Single threads placed one at a time
Contrasting in color and tone
When viewed from the weavers stance
Seem random and jumbled - meaningless
Laid in over time and with great effort
It asks us to wait, then step away
To discover the grander design

Satan’s Laugh – Part 2

This is part 2 of the story. Part one can be found here.


Jim picked up his M9, loaded a round in the chamber, dropped the hammer, pulled the magazine, and added an extra round from a few loose ones he kept in one of the pouches on his vest. There were three more magazines in various locations across his gear, all of them full, none of them ever used. The handgun was a backup, and he’d never needed it. Without having to even look, he quickly secured the pistol in the holster attached to mollie straps on the left side of his chest.

He next picked up his rifle, verified that the chamber was empty, sent the bolt forward, rotated the safety selector to burst, inserted one of his seven magazines with a slap, and gave it a tug to ensure it was locked in securely. All it would take was a quick pull on the charging handle and he’d be in business. It was a motion he had become very comfortable with over the last year. He clipped the rifle to the single-point sling hanging across his chest starting at his left shoulder, then turned to walk through that door for the last time.

He paused briefly and looked up again at the familiar lettering, including the rough blot of paint covering over the first two words. The red of the original was starting to bleed through the white patch, and it was legible to anyone who looked at it more than casually. Maybe that was a good thing.

Jim sat, pouring over the four-foot wide by six foot long printout he had spread across the table in the ready room. He’d been feeding all the information they’d collected into an algorithm he’d developed during his time in graduate school. The result was supposed to be a neat breakdown of known linkages and interdependencies. It was also supposed to identify the most likely points of intersection that had yet to be positively identified. Find an unknown intersection, and the odds were very good that it contained a high-level facilitator or leader. That was the theory at least, and it had worked excellently on the test data he had culled from the Al Qaida of 2001 and 2002. In fact, he could claim credit – at least in classified settings – for several very high-level take-downs in Afghanistan.

It was one of those take-downs, he was sure, that was responsible for him being here now. Damn that briefing. He should have kept his mouth shut.

Things were different here. In theory he was supposed to do real-time analysis and use that to identify and roll-up the next target before the enemy could react. The fundamental goal, he’d been told, was to use his analysis to map out the local leadership hierarchy and figure out where the head of the beast was so the Army or Air Force could decapitate it. The idea was simple. Someone was behind the persistent insurgency, and all he had to do was to work his way through the data to map out the clans, tribes, and other social structures that determined so much in this sixth-century culture. He was to use that data to find the head and cut it off (or at least a relatively small handful of heads). Do that, and the beast would die. That was the theory.

The reality was a little different. In fact, the more data he gathered the more fragmented and fractured the results became. As they rolled up one warlord or cell after another, the map began to disintegrate into small clusters of genuinely unimportant thugs. Had that disintegration come with a similar destabilization of the insurgency he would have called it a success, but it didn’t. Something was eluding him. There was a missing connection somewhere. There had to be.

His eyes swept back and forth, but kept coming back to a cluster of people the team had taken a few nights back. They all seemed to have some connection in common, but he hadn’t been able to get that information out of them. The people they’d found were mostly just shopkeepers and craftsmen who had been coerced by brutal threats. If he could convince them they had nothing to fear, if his team could take out their controllers, they might be more willing to talk.

“Warlock,” Jim said when he saw him enter the room, “I think we need to take a flight to Mercury. I want to talk to the guys we rolled up last week.”

“I’ll call in and see what we can work out,” Warlock promised and then left the room.

Jim continued pouring over his diagram for several more minutes until Warlock came back in.

“Chopper’ll be here in an hour. But it’s headed to Bucca. Your guys got transferred there last night.”

“Fine,” Jim answered, “if that’s what it takes. I’ll probably be gone a few days.”

Warlock nodded, then turned and left him alone with his thoughts. He spent the next hour formulating a strategy for convincing the four men that he already knew what it was he was after. He scanned the chart again, and again, making sure he understood the connections well enough that he could catch enough of their lies to corner them.

The helicopter arrived as expected, lifting off and banking away from the outpost before Jim had a chance to strap in. Once above the range of RPG and small-arms fire, the pilot leveled off and delivered as smooth a ride as can be expected in a Blackhawk. By the time they had landed Warwick had called ahead and explained the purpose of the visit, so a small team had gathered to meet him as he stepped away from the aircraft.

“Jones, S3,” said a tall, lankly looking Major who seemed to be the head of delegation, “but I go by Lurch most of the time. Warlock tells me you go by Shepherd.”

Jim grimaced. He’d been trying to avoid a call sign, but the team had recently branded him after asking what kind of rat-dog was next to the unicorn on the picture Lilly had sent. Immediately, a universal cry of Sheppard went up, and when he tried to protest they offered only one alternative… rainbow unicorn. Shepherd would have to do.

“Warlock and I go way back,” Lurch said by way of explanation. “Anyway,” he continued, “Grammar here will set you up with an interrogation room and will keep you company while you’re in the compound. He’s pretty new to the interrogation game, but from what I hear, you’ll end up doing all the talking anyway.”

Jim handed Sergeant Grammar a folder with info on the prisoners he wanted to talk to. “I’d like to see if we can talk to these guys today, then let them stew on what I tell them overnight and hit them again early in the morning.”

“Yes sir,” Grammar answered, handing the folder back to Jim. “Mister Warwick sent over the info electronically. Paper copies can be dangerous around here. Anyway, I’ll round ’em up as they leave chow. You’ll only get a few minutes each this round or else the other detainees will figure out that you’re talking to them. We’ll have to arrange medical appointments or the like tomorrow if you want more time.”

“That’ll have to do, I guess.”

“In the mean time,” Grammar continued, “I’ll show you to a rack you can use tonight, then I’ll take you to the chow hall for some hot food. It’s about the only advantage to working here.”

The thought of hot food brightened Jim’s mood significantly, and within a few minutes he was sitting at a table eating hot beef stew, fresh local flatbread, and cold ice cream with real utensils. He’d forgotten how much he liked food given that all he’d eaten for quite a while now was MREs. He stood and walked over to the ice cream machine to refill, then sat back down and ate it as slowly as he could without it completely melting.

Just when he was finishing up, Sergeant Grammar walked up and informed him that the detainees were prepped and ready. He stood and followed him to a nearby room built from concrete block and plywood containing nothing but a small table and three chairs. Jim took one of the chairs, and the interpreter (who had appeared seemingly out of nowhere) took another. Grammar turned and went out to collect the first detainee for questioning. Less than a minute later, he returned with a handcuffed figure who was unceremoniously dumped into the third chair. Apparently, Grammar would be standing.

“Remember,” Grammar cautioned, “anybody finds out who you are talking to, they might as well be dead. We can’t keep these guys out of the block for more than a few minutes today or their `mates’ will assume they’ve been talking.”

These pleasantries over, the interrogation started and continued for roughly fifteen minutes before the detainee was returned to their cell. This processes continued three more times in rapid succession. It wasn’t much time, but it was enough for Jim to make his case and plant the seeds of doubt he hoped would germinate overnight.

“Shephard,” Lurch said, lightly shaking Jim by the shoulder, “wake up.”


“We’ve had an incident.”


“Your boys are all dead. Targeted in their sleep.”

Jim sat up with a start, briefly believing the discussion had to do with his team back at the COP. “What happened?”

“Don’t know for sure, but at least a dozen other detainees used bed sheets to hold them down and beat them to death. Best guess is someone figured they’d been talking.”

Jim felt sick to his stomach. Still disoriented he asked, “What time is it?”

“0330. I know it’s early, but I thought you ought to know.”

“Damn. What next?”

“For now? Go back to sleep I guess. We’ll figure out logistics tomorrow.”

Lurch turned and quietly left the room. Jim rolled over and fell back into his customary restless sleep.

“What a waste,” Jim said to himself as he stuffed the few things he had with him in is ruck. “All I have to show for it is a few half-decent meals and a few more bodies in my count.”

As he moved to zip the bag shut, the contents of the folder that had contained dossiers were briefly exposed. The dossiers had been replaced. Almost hesitatingly, he pulled the folder from his bag and opened the cover. The pages that had been a picture and detailed description of low-level insurgent nobodies were indeed gone, replaced with copies of a flier advertising movies that played in the evenings when the chow hall doubled as a theater for off-duty staff. Someone must have switched them when he briefly left the table to refill his ice cream. Those men died because he decided to indulge in an extra helping of ice cream and had been careless with a piece of paper.

Warlock was waiting for him as he walked through the door into the ready room. He wanted to talk, but Jim was in no mood. He waved Warlock off, went through the room to a small maintenance area, retreived a can of paint he’d noticed a few weeks ago, and returned to the ready room. Pulling a chair over, he used a folded up wad of paper towels as a brush and painted over the first two words above the door.

“Plan to kill everyone you meet” was all it said now. Nothing about being polite, nothing about being professional, and now… nothing about having a plan. Each truncation of the original quote had brought the sentiment closer to the reality of this God-forsaken place.

“What’s your callsign?” Jim asked the driver.


“Capstone, slider,” Jim called over the radio mounted just to his left.

“Go ahead slider,” came the answer.

“Loaded up and headed out.”

“See you in a few hours. Safe travels.”

Jim put the microphone back and turned to the driver, “Lets hit the road.”

“I’m so lonely here,” Leslie sobbed uncontrollably. It was the first video chat in over a month, and it didn’t take long to confirm what he had suspected for a while. After the first admission, a string of confessions came out, each one piercing him. Making him feel like he had abandoned his family. It wasn’t what she had intended, but that didn’t really matter. Her herculean efforts to hide her pain, depression, and worry from him had collapsed.

“I’m so sorry,” was all Jim could say. He didn’t know what to say. There was literally nothing he could do.

“Everyone just assumes you’ve left us.”

It was too true, and it hurt to hear her say it. He had left, but not of his own free will.

“Let them assume what they want. You know they’re wrong.”

“I’m so tired too. Lilly cries herself to sleep almost every night, and she wakes me up over and over again having nightmares.”

“I’ve been worried about you.”

“And when I do manage to fall asleep, I have nightmares about what you’re going through over there.”

“Don’t worry about me, I’m in the best hands possible.”

“I need you. So does Lilly.”

“I need you too.”

The conversation continued like this for most of the next half an hour, during which time Jim felt more and more miserable and powerless every minute. Finally Leslie calmed down a bit, giving Jim a chance to think.



“Load the car up and go to your mom’s for a while. You need some help, and I can’t give it from here.”

“I can’t just leave the house empty,” she protested emptily.

The convoy had come to the outpost to deliver supplies, so neither the trucks nor the drivers were his guys. The only people he knew were K9, Killroy, and Cooter who were each in a different vehicle. That was a mixed blessing, he decided. If something happened to one of them, it would only happen to one of them. On the other hand, he didn’t know the crew of his truck, and so didn’t trust them particularly.

They drove onward without a word among the crew for several miles before the driver broke the quiet.

“I heard you rolled up a bunch of the Sadr organization.”

“Not so much Sadr, they seem to have stayed in their sandbox.”

“But you got a lot of bad dudes, right?”

“Ba’athists, old-fashioned Al Qaida, Iranians, Yemenis, Saudis, Palestinians, Chechens, Americans, Brits, Canadians, Pakistanis, Turks, Uygurs…” he trailed off as if to say there were plenty more.

“Roads have been pretty quiet. We should be in Ramadi in about 40, and have you in the Green Zone within another two hours after that. Maybe an hour and a half.”

Jim just nodded in acknowledgment.

“You rotating home?”

Another nod.

“Gotta be nice. The rotator leaves tomorrow, so you won’t even have to stay in Baghdad longer than overnight.”

“I’m not on the rotator,” Jim admitted. “My flight leaves as soon as I make the plane.”

“Sir,” Warlock said as he approached from behind.

“Don’t tell me,” Jim said acidly, “another hot tip like the last one.”

“About sums it up.”

“When was the last time we had a hot tip from someone that actually panned out to be more than a small-scale IED factory? About the only good tips we’ve ever gotten we’ve developed on our own.”

Warlock shook his head silently. Truth be told, almost all the hot tips turned out to be nothing at all except an excuse to survive another ride into the hostile unknown.

“Never mind. I don’t suppose it really matters,” Jim said, cutting himself off. “This one might be the final straw that breaks the insurgency, right?”

Warlock twisted the corners of his mouth into a doubtful lopsided grin. “Yeah, I suppose so.”

Both of them had become jaded over the last several months. The hope they had of making a real difference had been trampled by hard experience. It was a sure sign that it was time to find someone else for the job, but unfortunately, that didn’t agree with CENTCOM’s calendar masters.

“Well, let’s go fishin’ I guess.”

The team spent several minutes doing what by now was completely routine planning. Ingress and egress routes, locations for security pickets, identifying who would be on the entry team. It was all so familiar any of them could have done it in their sleep, and this particular neighborhood had become so frequent an objective that they really didn’t need the map.

“Cookie cutter,” Monkey observed.

“Wrap and pack,” K9 agreed.

“Careful,” Warlock warned, “don’t get lazy. That’s a good way to get killed.”

They all silently agreed, and went back about their business. Within an hour, the entire team had assembled their gear, loaded the trucks, and were ready for departure. Now it was just a matter of waiting until the witching hour. Everyone except warlock and Jim found a semi-comfortable position in the ready room and tried to sleep. There really wasn’t any better way to pass the time, and they had all mastered the fine art of sleeping on command. They planned to be on-scene an hour before sunrise.

“You should try and get some sleep,” Jim cautioned.

“And you shouldn’t?”

“I snuck in a nap earlier today,” Jim lied.

“Yeah, me too. While we were standing with our eyes open.” Warlock was starting to look tired. Not sleepy, but tired in a much deeper sense of the word. Jim was pretty sure he looked even worse himself.

“What do you have to go back to?” Jim asked. They’d never talked about home before, but somehow it just seemed like the time to ask.



“Nothing. Wife left me two deployments ago after selling off everything I owned. Blew all the cash on drugs before I got home, so there wasn’t anything to argue over in the divorce. We never had kids. Parent’s died a few years back while I was in Afghanistan. This is all I have left. I’ll probably start angling for another deployment as soon as I get back.”


“What about you?”

“Wife and kid.”

“I know that much,” Warwick admitted. “They surviving okay?”

“Not really. Timing was really bad for my family.”

“So I see the Air Force cares about as much about that kind of thing as the Army.”

“We’re just numbers,” Jim said flatly. “The bean-counters don’t see you. All they see is an MOS, rank, and date of last deployment.”

“What you goin’ to do after this?”

“Dunno. I’m kinda worried about being around normal people again.”

“It takes a while,” Warwick admitted before turning a crooked smile toward Jim. “Most people on the outside frown on caressing an M4 in public places.”

Jim stopped, realizing he had been doing exactly that. Warwick just laughed quietly and gave his own rifle a pat. Those inanimate pieces of black aluminum, steel, and plastic were some of the closest friends anyone on the compound had. If given the choice between a supermodel and their rifle to take to bed, most would pick the rifle at this particular point in time.

“Why do you always take point when going into a building?” Jim asked. He’d noticed the unusual behavior quite a while ago, but had never asked.

“If anyone’s going to take it in the face on my team, I don’t want to live to see it. They’ve all got something to go home to or at least look forward to. Me… all I have to look forward to is an aluminum box, a flag, and a last salute at Dover.”

Jim just nodded with a sense of finality and understanding, then changed the subject to ask about Warwick’s pre-army life. The two talked for another hour before Warwick started nodding off like the rest of the team. It was the first time Jim had talked of home with anyone, and it was something of a relief. Being the only officer on the outpost could be extremely lonely. Everyone was respectful, but there was a barrier there. He’d never have the kind of brotherhood that existed between the other team members. Now with Warwick asleep he was alone again with his thoughts. He had come to hate that condition.

It didn’t last though. The next he knew, he was being nudged awake. Dreamless sleep. A rare luxury. Dreams lately were either nightmares or just made him long for home and things that couldn’t be. If he could have found a way to satisfy the physical need for sleep without ever having another dream he would have instantly traded away the best dreams he’d ever had for a few nights of quiet rest. None of that really mattered at the moment, though. It was time to load up. Everyone silently geared up, mechanically checking and re-checking weapons, ammunition, armor, and anything else they relied on. Then they shuffled to the waiting trucks.

“QRF’s on standby,” K9 reported.

“Let’s get this over with,” Jim directed. On-command, the trucks all started and began rolling towards the gate without headlights or anything else that might give away their position and intent. A few minutes later they arrived at the objective and the full team rolled out of the truck in a single motion. The pickets set up a perimeter while the breaching team blew the lock with a 12 gauge shotgun and a swift kick. The clearing team entered the house and began sweeping from room to room. Jim and the remaining team members followed a few meters behind, carrying what had become their standard forensic equipment – essentially just a computer and cameras – in addition to their battle rattle.

As the clearing team entered a small room, Jim heard a deafening explosion and chunks of concrete pelted him in the face. He hurried to the source of the explosion, scanning carefully as he entered the room to ensure there weren’t any tripwires or pressure plates.

Warwick was down. So were Monkey and Mutt. In the middle of the room was a mangled upper torso and head of a young child. He couldn’t have been more than six. Some sick son of a bitch had rigged the kid with a suicide belt.

“Wolfpack three, wolfpack one,” Jim said into his radio.

“Go for three.”

“We’ve got three down. Call for immediate medivac, and get the QRF en-route.”


“The building hasn’t been cleared yet. We’re going to hole up where we are until help arrives.”

While Jim made the radio calls, K9 and Killroy were already down and working on the two younger soldiers. Jim moved over to Warwick and started assessing him. There was a blood-tinged clear liquid dripping from his nose. He was totally unresponsive.

“Don’t quit on me Warlock,” Jim shouted angrily.

“Monkey’s gone,” Killroy announced.

“What about Mutt?”

“Not dead sir, but pretty roughed up,” K9 responded. Mutt hadn’t been fully in the room when the blast went off, and had been partially shielded by the wall. He was bleeding from his ear, and had several deep cuts on his face and arm from shrapnel. He would be going home, assuming he survived. K9 had just finished tightening up the windlass on a tourniquet, and was working to bandage the more severe wounds on his arms.

Killroy came over and took over Warlock’s care. “He’s in a bad way sir. But if he can make it to Balad, I think he’ll have a chance.”

Gomer, who had stepped into the room to help with the injured, looked at the scene and growled angrily, “he’s lookin’ at a full-on comedy tonight. Just roaring with laughter.”

Jim turned and looked around the room. No bomb making equipment. No computers. Nothing but the fragmented remains of a little boy. The only addition to the room that he hadn’t seen on his initial entry was another body, a woman wrapped completely in a black shawl except for her hand. In that hand was an improvised switch with frayed and burnt wires laying on the floor. Jim was certain there would be propaganda claims on the streets before they got back to the compound that his guys had killed the both of them.

“Been uncommonly quiet on this corridor lately,” the driver said over the drone of the engine and other road noise.

“Sorry, what?” Jim hadn’t been listening.

“I said it’s been pretty quiet in this sector for a while now,” he almost shouted.

“We’ve spent months trying to shut down that kind of thing. Both Bucca and Abu Ghraib are full of guys who have a vendetta against my team.”

He couldn’t bring himself to share the fact that the end result of all that work hadn’t really been a reduction in the number of roadside bombs. If you actually looked at the numbers, the current lull was nothing more than a statistical anomally. In fact, he’d been able to show pretty conclusively that all his work had done was to break up the larger and more organized cells into smaller and more independent units. It was like the mythical hydra – for every head they had cut off at least two new ones had grown back in. Not only that, but with every dead leader or shut-down cell the newcomers got wiser and wiser about staying out of sight. The hunting had been difficult lately. Worse, they had been hunted.

They were down three. Three in a single mission that hadn’t even resulted in any useful outcome. The three most experienced men. Two were gone forever. Why? What purpose had their deaths served? He didn’t have an answer.

He’d just gotten off of a phone call with Leslie. Lilly had refused to even talk to him, and only screamed when Leslie put the phone to her ear. He knew at some level that it was just the nature of a seven year old, but it still hurt. Hurt more than he dared let on. Thankfully, Leslie had told him she’d started sleeping better, and had quit talking so much about the possibility of her dad dying. He hoped it wasn’t because she was forgetting him… but he had his doubts. It had been almost a year since he’d spent more than a few days at a time with her.

The conversation with Leslie hadn’t gone particularly well either. He couldn’t say anything about the failed mission the week before. Couldn’t tell her about the image of the little boy haunting him around every corner. He couldn’t tell her about how close he was to being in the room when the blast occurred. In short, he couldn’t tell her anything. It stayed bottled up inside of him. On the other hand, she had broken down completely. In fact, most of the conversation had been nothing more than the sound of her crying. He felt like a miserable failure.

He’d failed at finding the mythical center of mass for this elusive enemy. He’d failed to protect his team. He’d failed to see the pattern of testing their responses that had resulted in a series of tips that went nowhere but revealed their operational techniques. He’d failed his family by leaving them. He’d failed himself, though he couldn’t put his finger on exactly how. He’d failed to find any meaning in this war that was progressively sucking the life out of him and everyone around him. Failure all around. What was the point?

He looked at the holstered M9 on the shelf. Every time he’d picked that weapon up lately he had flashes of fear – usually accompanied by images of him using it on himself. Sometimes those images would invade his sleep. Sometimes they persisted well after he’d put it out of sight. Always, at least so far, he’d managed to write it off as irrational. Lately, those images came accompanied by little visual snippets like the rolling eyes of the girl killed on his first raid. Were humans worth saving? Nobody else around here seemed to feel any need to value human life… why should he?

He’d seen the lights go out in people’s eyes enough times now to know how death progressed. Put the bullet in the right place, and all it would take is a single trigger pull. He’d never even hear the blast. Wouldn’t feel anything. It’d just be over. What would that be worth?

His memory told him he once believed it actually wouldn’t be over, that there was more after this life, but none of that made sense in the context surrounding him. How could it? He couldn’t remember at the moment why he’d ever believed. Couldn’t remember what it had felt like to believe. Couldn’t believe. If there was a God, how could he let people become this depraved. If there was a God, why would he take so much away from him. If there was a God, why would God abandon him and leave him on his own. That sense of abandonment, the sense of being cut off, the knowledge that it didn’t used to be that way. Those things hurt deeply.

He thought about how it would hurt Leslie, but that didn’t make sense either. Every raid the odds of him coming home in a box increased, and that was apparently acceptable. He could roll out tomorrow night and never come home. Everyone accepted that. However, if he did die on-duty she’d never know exactly how or why. Too much of what he did was classified. If he died here, on his own terms, he could leave a note at least so she would understand. But then, there was no way he could write down what he felt… he didn’t even understand it all, little lone know how to communicate it.

Then there was the reality of going home. It terrified him. Assuming he survived, he wasn’t the man she had married. He was broken. He was very broken. Wouldn’t it be easier for her to deal with the death of her husband in a war zone far far away than deal with the dead, but still ambulatory, one the Air Force would return to her?

And Lilly… wouldn’t she be better off if Leslie got remarried to someone who could be there for her? She was young enough that she wouldn’t even really remember him in the long-run.

He slowly and deliberately reached for the pistol and unholstered it, turning it over and over in his hands, looking at it, feeling its weight in his hands. The metal felt cold and smooth against his skin. It’d be easy, he told himself. Everyone would be better off this way, he told himself. It was the only way to fix things, he told himself.

He ejected the magazine, checking to make sure it was full. It was. He reinserted it. He checked the chamber. There was a round in the pipe. The safety was off and the hammer down. It would be a long trigger pull. He cocked the hammer to make it lighter. He put the muzzle in his mouth, pointed slightly upward. The metallic taste made him gag, and he set the pistol back down. “You insignificant, weak, stupid man,” he told himself, throwing himself backwards in the chair in disgust. He was a failure at even this.

He reached for the pistol one last time, determined not to let anything stop him. Just as he got a firm grip, and was lifting it from where he’d set it, a booming voice rang out.

“Sir, put the gun down!”

K9 was standing just to his right. Lost in his mental abstraction, he hadn’t heard the giant approaching. Before Jim could do anything, K9 had put one enormous hand on his shoulder, and the other on his wrist, pinning it against the table until Jim let go of the gun.

Jim collapsed into the big man’s arms, sobbing uncontrollably.

The convoy had entered the outskirts of Ramadi. It was a ways from where their outpost had been, but he knew the streets here very well. How many times had the come down here to roll someone up. As he surveyed the destroyed buildings on either side of the road, he tried to remember just how many his team had been responsible for. It couldn’t be that many… Maybe two or three dozen? Fifty at most. Either way, it was a drop in the bucket.

Seeing the place in the daylight was different. Almost every time he’d been here it had been between one and four in the morning. Black. Most the rest of the times he’d flown overhead in a helicopter. It looked bad from the air, and bad in the dark, but the sun shone light into corners that were otherwise invisible. Corners that looked much better unseen. You couldn’t see the kids playing in the rubble from a helicopter. At least not well enough for it to really sink in.

He wondered why anybody had stayed here when things got hot. Why would you stay somewhere that was killing you (slowly or otherwise) when everything you had or cared about was being taken away? Why not pack up what you could carry and leave?

Sitting at his desk, he opened the ruggedized laptop and logged in. The process generally took several minutes, and once the login was complete, it took several more minutes for email to update over the sketchy internet connection here. He stood and stepped to the door of the hooch, squinted against the intense sun. Nothing had changed. At least not visibly. Everything was sandy brown and outright ugly. He had two months left here, but going home was just as scary as staying here. He felt stuck in between. Between what, he couldn’t have told anyone, but one thing he could say with certainty was that there were few places in the world he hated more than this small outpost in a destroyed city in the desert. But it wouldn’t do to think those thoughts now. He still had to survive two more months.

Returning to his computer, he found that email had updated, and that there was one from Leslie. He opened it fearfully, but hoping for good news. She had been so low the last time they talked. The way she talked she wasn’t doing any better than he was. He wondered if he would ever be able to tell her about his own struggles, but decided they would remain his own for now at least. Sharing that burden with her wouldn’t lighten his own load and would only make things harder for her.

As he read a small burden lifted. She’d been thinking about what he’d told her and had decided to take Lilly and make the road-trip to her mom’s house in Idaho. It was a solid two-day drive from San Antonio, but she had made arrangements to stay a few days with friends from a previous assignment who were currently living in Albuquerque. Her plan was to stay at her mom’s house until he got home.

“Good,” he thought, “I need her to have the help.”

As the convoy left Ramadi, Jim thought to himself how quickly the relative green of irrigated fields evaporated into barren desert. He was so tired of the brown. Especially the empty, wasted, barren brown of a God forsaken desert. Why would anyone fight over this place. What drove men to do that?

“Gomer,” Jim said angrily, “what do you mean?”


“What gives you the right to talk about laughing when we’re in the middle of shit storms. Every time something goes really wrong, you start talking about laughing.”

“That’s Satan’s laugh, sir.”


“If you listen, you can hear Satan laughing at the awful things men do to each other. Sometimes it sounds like gunfire, but usually I don’t so much hear it as feel it.”

Satan’s laugh. He could hear it now. Gomer had been the first in the team to recognize it, but now everyone else understood and recognized it. For months now, they had started every mission with a silent prayer of “Lord, no laughing tonight please.” He had uttered those same words under his breath as he had been climbing into the truck he was now in.

The worst thing for Jim was that he now he heard it all the time. It didn’t matter where he was or what he was doing, he could hear and feel that cackling hateful laugh. He could sense the devil’s glee in the destruction, moral breakdown, and general despair all around him. It helped him understand why Gomer was so quiet all the time. It also made him feel empty and angry, and it was his most constant companion.

“Sir,” K9 said, sticking his head inside the hooch.


“We’ve got an unscheduled chopper coming in about half an hour.”

“What for?”

“Didn’t say, other than to make sure you were here when it arrived.”

Jim couldn’t help but wonder if word had gotten out about his near suicide. Maybe he was being relieved. Had he failed that badly?

Maybe it was an investigation of the raid that had killed Mutt and Warlock. Would they be here to accuse him of failing to take care of his team? Would they try and pin the blame on him for not recognizing the pattern of testing and response that had preceded the deaths?

His mind raced from one scenario to another, and back again. How could he know anything based on the description K9 had given him? That ignorance did nothing to stop his mind from attempting to fill in the blanks with anything and everything… just so long as the end result was bad and pinned on him.

Jim turned to his work and tried to distract himself the way he generally did when thoughts took on a life of their own. It wouldn’t work. His ability to shut out the unwanted was failing again. He stood, walked outside, and began pacing the yard – weaving in and out of the trucks and barriers. Movement helped, but it wasn’t enough. He continued to pace nervously until he heard the thumping of a helicopter in the distance. He turned and scanned the sky, searching for whatever was coming.

Almost without warning the helicopter appeared just beyond the outer wall of the compound and swept past in a wide arc, climbed a bit, then slowed to a hover directly overhead and gradually came down. As the gear came down to about head-height everything disappeared in a cloud of dust. It always happened this way, but that didn’t make him feel any better about it. Anything that blocked his visibility was becoming a problem for him, and this particular scenario was particularly bothersome. As the dust settled, three men stepped off the helicopter. Two of them approached him, and the third moved towards Lowry.

“Major Harwood,” the Colonel said, extending his hand with the greeting.

“Sir,” Jim answered, shaking his boss’s hand.

“Do you have a place we can talk for a minute?”

Standing next to the Colonel was a chaplain he’d never met before. A Colonel with a chaplain in tow was a bad thing that had only occurred once before when Warlock and Monkey died. Immediately Jim began to steel himself for news that Mutt had succumbed to his injuries as well. The team didn’t need this right now.

“We can send everyone out of the ready room if we need to, but there isn’t really anywhere that will be private,” Jim said. “Even if there were, there aren’t any secrets with much of a lifespan around here.”

Apparently the Boss didn’t plan on staying long, otherwise the pilot would have started shutting down by now. As they turned to walk that direction and escape the noise of the still idling helicopter, the third man said something to Lowry who then directed several of the men to unload a few bags.

“I can’t stay. A major dust storm is only a few clicks away and inbound. Once it hits, we’ll be grounded for a while.”

Jim nodded acknowledgment and glanced over to where the third passenger was talking with his team.

“Specialist Maples’ replacement,” the Colonel said, answering the slient question. “Most of your team already know him from Bragg. He’ll fit right in.”

“Mutt will be hard to replace,” Jim said. He was waiting for the bad news, and decided to push the point rather than wait for the boss to get around to it. “Have you heard how he’s doing?”

“He made it alive to Landstuhl,” the Colonel said sadly, “but I don’t know any more than that.”

So this wasn’t about mutt… and it left Jim wondering what else this could be about. The Colonel didn’t wait long to relieve him of his curiosity. As soon as the door to the ready room closed behind them, hushing the worst of the noise, the Colonel half sat, half leaned against a table and asked Jim to sit down.

“Jim, we got word a little over an hour ago through the Red Cross. Leslie and Lilly were killed by a drunk driver last night outside Shiprock New Mexico.”

An explosion a few yards in front of the truck blew a large crater in the road and threw an enormous amount of dirt into the air. The driver, unsure how to get past the hole, slowed to a halt.

“Don’t stop now!” Jim shouted, but the driver never heard him.

Satan’s Laugh – Part 1

Packing Up

He sat on the edge of his cot, rifling through the papers that had been collecting in the small corner of the hooch he used as an office. Reports, maps, dossiers, printed emails… worthless – all of it. As he worked through a drawer full of folders, only glancing at one after another before adding the contents to a growing pile, he paused on a rather thin one and pulled out the few papers that were inside. These he would keep, nothing else. Setting them aside, he grabbed the rest in single motion and threw them down on the discard pile without inspecting the contents. He felt an intense desire to burn the few he’d held back, but they were necessary until he had processed out of country. He looked again at the pile of discarded work and picked up a memorandum peaking out of the folder on top. He held it up, staring at it briefly before crushing it in one hand with all the violence and malice he could muster, his forearm and fist trembling with the exertion.

“Major Harwood,” SSgt Meyers said, standing on her tip-toes so she could just peak over the cubical wall.

“Yeah?” Jim asked without looking away from the report he was desperately trying to finish before calling it a day. He had been staying late for the last week in order to wrap this project up. It was his first formal product since checking into the unit, and he wanted it to make a good impression. The thought of it hanging over his head for a three-day weekend was too much to bear, so it had to be done this afternoon. He had also promised Leslie that he was hers for the full three days, starting with dinner at her favorite restaurant later that night.

“The Colonel needs to see you.”

“Coming,” he said, saving his work and simultaneously standing and stretching his back. “I probably need to step away from this for a minute anyway.”

He followed her to the Colonel’s office. The boss, standing in the doorway waiting, motioned for him to enter and gently pushed the door shut with his foot after they had both crossed the threshold. The grim look on the Colonel’s face didn’t bode well for Jim, but racking his brain didn’t result in anything that could explain this unusual interview.

“I debated holding off until after the weekend,” the Colonel started, “but I think you’ll need all the time you can manage.”

Jim stared blankly, trying to figure out what on earth he’d need the weekend for that could possibly involve the boss. All he could manage was a quizzical “Sir?”

“You’ve been tapped for a short-notice deployment. Came down this afternoon.”

Jim felt the weight of every book, plaque, trinket, piece of furniture, and other movable object in the office come crushing down on his heart and lungs. He’d been non-deployable for years due to the nature of his previous assignments, and knew that he was due. However, he had hoped for a bit more than the minimum 45 days on-station prescribed by policy. They’d only just found and moved into a rental that Friday and boxes were still stacked everywhere waiting to be unpacked.

“You’ve got two weeks until you need to report for pre-deployment training,” the Colonel said as he handed Jim a manila folder that apparently contained information about the deployment. “Don’t bother with any more work here. Get going with outprocessing and spend the rest of the time with your family.”

“Yes sir. I’ll start making arrangements,” was all the reply he could muster.

He turned and left the office, walked back to his desk and flipped through the paperwork. Checklists, training requirements and dates, and a letter from the CENTCOM J3. As was his custom, he glanced at the letter in it’s entirety looking for anything significant in the structure. Immediately a few features caught his eye. First, it was a scan of another document. The general had personally lined through the traditional introductory “Major Harwood” and written “Dear Jim” in ink above it. This kind of personal touch was usually reserved for congratulatory notes on birthdays and such. It was also wet-signed in blue ink and dated by hand with the same pen only the day prior. This was a rather marked deviation from the much more ubiquitous and impersonal digital signature the DoD had been adopting for everything.

This whole thing felt funny. As far as he’d ever seen, deployment taskings didn’t come in a manila folder, generally requested a generic capability instead of targeting any specific individual, and weren’t lavished with personal attention from one of the busiest generals in the DoD. He turned back to the papers that described the scheduled training and started scanning the familiar format looking for the few bits of real information buried in bureaucratic formality. Defensive driving, two different urban combat and small-team tactics schools, three months at DLI learning Arabic, SERE training. This list was significant and disturbing given his background and the associated role guys like him typically played in a combat environment.

Having completed this exercise, he returned to the letter and read through its contents carefully. It described an experimental program designed to break down Al Qaida by embedding analysts like him with special operations teams. It was supposed to shorten the analysis timelines and get inside the enemy’s OODA-loop – there was a term he hadn’t heard in a while… “Observe, Oreint, Decide, Act.” Whoever wrote this was clearly somewhat long in the tooth. Boyd’s work hadn’t been all that popular in military culture for years. In fact, the last time he’d seen that term he was still in ROTC. This brain-child may actually have come from the general himself.

He had been individually selected for this assignment, the note said, because of his experience and demonstrated prowess at tracking and analyzing the clan structure and tribal alliances in the specific region where he was being assigned. That meant Iraq, almost certainly Al Anbar, and probably Ramadi. There weren’t any worse places at the moment. If there was going to be a major firefight and significant casualties on any given day, the odds were pretty good it would be there.

He had spent the last five years since 9/11 becoming the Defense Intelligence Agency’s top expert on the people of that region, and had made a name for himself almost by accident. He was supposed to be a Korea expert when he checked into his unit, but there wasn’t much new to do on that front so he’d branched out to keep himself entertained. When the Pentagon began seriously prepping for the invasion he had been asked to present some of his analysis to a small group. One of those in the room at the time owned the signature on this letter. He’d been specifically tasked, by name, by someone almost nobody could refuse.

While this information explained why the Boss hadn’t tried to reclama and keep him home a little longer, it really didn’t make him feel any better. He was going to leave his wife and daughter to fend for themselves for almost six months of training followed by another six months of deployment. The previous year had left them all fragile, and now, when things had finally begun to settle down, he would be leaving them alone in a new city far away from friends, family, and help. Why couldn’t they have at least told him before they moved? He could have left them in Virginia where they had a functioning support network.

The extensive list of pre-deployment training was highly unusual too. Staff weenies working in Qatar or even Baghdad and Ramadi didn’t need that kind of training. He briefly toyed with the idea of hiding the nature of the deployment from Leslie under the formalism offered him by the “data masked” location, but he quickly put that thought aside. He knew she needed to know the full truth, and would find out eventually regardless. However, knowing he had to tell her wasn’t enough to guide him on how to do it. How could he break this kind of news to her given what they’d just been through? He dropped the folder on his desk and walked dejectedly out of the office.

Surveying the pile of paper, he realized that everything he’d been working on for the last four months existed digitally now. Paper was pointless. Even in digital form, he was convinced, its value was questionable. Yet these white ghosts bleeding with black and blue ink had been piling up since he got here. White ghosts were his business, but he had come to realize that they were absolutely irrelevant. He grabbed the whole stack and walked it outside to the already lit burn barrel and threw it in. As the papers on the outside layer charred and began curling in the flames, he caught sight of one paper underneath he hadn’t intended to include. It was a simple sheet of copy paper, but instead of toner from the printer or ink from his pen it was decorated with crayon.

In a silent panic, he plunged his hand into the barrel and retrieved the errant piece of paper, dropped it on the ground, and quickly but carefully pushed sand over it with the toe of his boot to extinguish the flames that were curling the blackened edges. Retrieving the paper from the sand, he looked at the damaged artwork and raged within himself over his lack of attention and the near loss of so precious an artifact.

“Hey Boss, we’re done unloading. Mail came in too.”

“Anything interesting?” Leslie had told him she had sent a care package a few weeks ago, but he’d almost given up on ever getting it. Deliveries to these small outposts could be erratic at times.

“Not for me, but looks like yours is here,” he said, tossing the package to Jim before ducking out to let him open it alone.

He paused for a few moments, looking closely at the curved and neat handwriting on the label. He sniffed the box, hoping without reason to smell something other than the world around him. Having completed these rituals, he pulled a pocket knife and carefully sliced through the packing tape. He set the knife down and gently unfolded the cardboard flaps to expose the inside. On the top of the open box sat an envelope that was decorated with large hand-drawn and lop-sided hearts and addressed in purple crayon by an unmistakable and very young hand. He’d start there. He again picked up the knife and inserted its blade into the envelope, cutting a clean slice down its spine. As he lifted the enclosed paper free of its wrapper, a ridiculous amount of red, sliver, and pink glitter spilled out, covering both his uniform and the floor of his hooch.

Shrugging off the almost impossible to clean up mess, he turned to the letter. The team would never let him live down the glitter no matter how hard he tried to clean it off, so why bother? On the front of the paper was a highly embellished stick figure unicorn, what looked like a smiling dog – probably their German shepherd Lola – and several brightly colored butterflies framing a few words written in a rainbow mixture of crayons – “Dad, I love you. Please don’t die.”

He initially grinned at the simplicity of a six year old, then turned the paper over to read the few lines penned much more neatly on the back. “The magic of the unicorn is supposed to keep you safe, and Lola is there to protect you. The butterflies are just because they’re pretty.” Before looking at the rest of the package contents, he walked to the wall of his hooch and hung the paper proudly on the wall. Standing there looking at his new protectors, it sank in just how much was contained in that simple picture. Sammie was worried. She knew he was in danger, and didn’t know how else to express it other than to call on the only magic she understood. How do you console a child who barely knows how to share their grief and anxiety? Plumbing his feelings and experiences, he came up dry; so he turned to Leslie’s letter hoping for something else to brighten his day.

His hands trembling with a mixture of eagerness and fear, he opened the envelope and began to read. In the opening passages Leslie included the traditional declarations of love and longing. It always made Jim smile to read these. She was a marvelous woman, and he missed her intensely. She then addressed typical business items like doctors appointments, activities at church, and news from family members. His spirits started to droop as he realized what wasn’t included. It didn’t look like it would be included. He read on hoping he was wrong until coming to the end without satisfaction. She had said nothing about how she was doing. Nothing about how she was adapting. Nothing about how she felt beyond wanting him to return home safely. The nothing spoke volumes.

Jim looked at the pile of uniforms and other stuff now piled on his cot, contemplating just stuffing them randomly into the duffel bag instead of neatly folding and organizing them. They all would be trashed when he got home anyway, and he wasn’t all that sure why it made sense to drag them that far. None of that mattered, though. After briefly stuffing a few items haphazardly into the bag, he reversed course and decided it would be easier to get everything in if it were neatly done. He then emptied the bag and mechanically folded and packed each item.

Fumbling blindly in the desk drawer near his cot, he pulled out his padlock, folded each of the grommets around bag’s opening over the metal fastening loop, and latched the lock through the loop to keep it all together. That was the last of the packing. He stood slowly and stepped back to contemplate the result. The strip of duct tape inscribed with his last name in permanent marker was still there from the last time he had packed this particular bag months ago. In fact, if it weren’t for wear and tear on the contents, he wasn’t sure there would be a distinguishable difference between this bag and the one he carried when he left home.

“Major, welcome to COP Nowhere!” CW2 Warwick shouted over the roar of the rotor wash and turbine noise as he picked up the decidedly new duffel Jim had kicked out of the helicopter. Jim had been able to see Warwick as they approached the landing zone right up to the point where the open door was filled with flying dust. Warwick had been standing with his M4 hanging vertically in the center of his chest from a sling, his bare arms folded across his chest and the palm of one gloved hand resting on the butt of his rifle. He was positioned just off to the side of the improvised helipad with goggles covering his eyes and the remainder of his face covered by a tan and black Keffiyeh. Jim wasn’t sure how the pilot had any idea what was below or around him, even less idea how Warwick had been able to see enough to approach the helicopter. It made him nervous to ever get back into a helicopter in this barren desert. Somehow Warwick had navigated through that dust, and he was at the door by the time things settled enough to see more than a few inches.

“Mr. Warwick, good to be here,” Jim lied.

“I go by Warlock. You’ll find everyone here uses a call sign. You’ll earn one too, soon enough…”

The two stepped to the side, silently acknowledging that any further conversation would be best suited for after the delivery bird left. Immediately, a crew of six men from the outpost rushed to the helicopter, forming a bucket brigade and quickly unloading the weekly supplies along with Jim’s gear. Within five minutes, everything was piled up a few meters away and covered with a tarp.

“Sir, you might want to turn around before he powers up,” Warwick shouted when the crew was done unloading. “You don’t have the right kind of protection on, and it wouldn’t do to evac you on your first day because you got sand in your eyes.”

Jim turned around, and right on queue the pilot powered up. Sand with characteristics identical to materials ranging from talcum powder to pea gravel began to pelt him from every direction, completely filling every exposed bodily orifice almost instantly. He instinctively buried his head in his arms and took a knee with his back to the now quickly rising helicopter in an effort to protect himself. Then, as the rotor wash faded away, Jim stood and turned to watch the green shape climb to altitude and turn back to the main base, abandoning him in this hell-hole far from all comforts and most help.

He looked around the hooch, scanning for anything he had forgotten… anything he actually wanted or was required to return. His bags were packed and had already been loaded on one of the trucks, but he couldn’t quite convince himself he wasn’t leaving something behind. He looked under and behind the few pieces of furniture. Nothing. There wasn’t really anywhere else to look, but he kept scanning back and forth trying to be sure.

“Sir,” Killroy said, sticking his head in the door and grabbing the duffel, “let me take this to the truck.”

“Oh… yeah,” Jim said, “Thanks.” He hadn’t heard the normally boisterous hothead approach. Either he hadn’t been listening or Killroy was being uncharacteristically quiet. He turned and followed the young Sergeant as he walked over to where the convoy trucks were staged.

As they were crossing the compound an explosion shook the area immediately outside the sand-filled barrier directly across from them. This was followed by a dull thud from off in the distance to their left. A mortar, apparently, fired from somewhere relatively close. Neither man reacted much, but continued what they were doing as if they were completely oblivious to the sound other than a sideways glance at each other and a slightly raised eyebrow from Killroy.

With a half-grin, Killroy silently counted backwards from five on his fingers. Before he had folded the last finger into a fist, there was a short whistle and a much louder thud – counter-battery fire from the artillery unit nearby. Five more followed in quick succession. For the life of him, Jim couldn’t figure out why anyone would lob a mortar anywhere near the FOB. The futility of doing something you knew was likely to result in your corpse being picked up with a vacuum or a spatula (if at all) didn’t seem to register for the seemingly infinite supply of gullible young men who had been manipulated into believing it was Allah’s will that they be liquefied by the US Army. What a waste.

“This round’s only worth a chuckle,” Killroy said matter-of-factly.

“Par for the course,” Jim answered flatly. “Hopefully today’s comedy doesn’t make the old’un break out into a full laugh again until after we make it back inside the wire.”

Killroy nodded agreement and shifted his course towards the trucks.

“Tell the drivers I’ll be ready in a few,” Jim said as he turned towards the ready room. He had a few things to do before they could depart. Killroy nodded, but didn’t say anything.

“Dinner’s ready,” Mutt sang out as he walked through the ready room tossing MREs out of the case in his hands, each one landing expertly in front of whoever it was intended for.

One by one, the team slit open the heavy plastic envelope of food and started inspecting the contents. Jim’s was a ham and egg omelet, his least favorite. In fact, that particular menu item was so despised that nobody even bothered asking for a trade when they got stuck with it. You just knew that whoever drew that particular honor was stuck with it. About the best you could hope for was that someone would be kind enough to donate an extra ration of Tobasco to cover the flavor. You couldn’t do anything about the texture except warm it up, and that was rarely worth the work. Maybe he’d do without the main entré tonight and satisfy himself with the crackers and other such stuff.

Suddenly a crashing, whizzing sound tore through the air, followed immediately by the bang of an explosion. A mortar had landed just outside and shrapnel had torn through one wall, shattered one of the fluorescent light fixtures, and stuck in an opposite wall. Jim dove to the ground and covered his head with his arms, waiting for further impacts. He heard additional thuds of distant explosions, then silence. Nothing else came near. After what felt like an eternity of quiet, he peeked out from under his arms to see the entire team still sitting or standing upright and watching him silently.

“If you hear it,” Warlock said calmly, walking to the wall and using the pommel of his knife to knock a two inch piece of hot jagged metal loose, “it’s nothing to worry about.”

“They never lob more than one at a time,” someone called Monkey added, “because that would take the odds of surviving the payback from bad to zero.”

“Finish your food,” Warlock directed to the room in general before turning back to concentrate on eating his own.

“Sir,” K9 said with a light touch on his shoulder. Staff Sergeant Kelnhoffer was a mountain of a man who could fill a room without saying anything, and when his physical presence combined with his voice it tested any safety margins engineers may have put into the walls and ceiling. But here he was gentle in a way that might have stirred ideas of a giant silver-back gorilla caring for one its young. Might have, that is, if anyone had been aware enough to notice. Jim wasn’t. He barely stirred at the touch while staring blankly at the doorway in the opposite wall. The doorway that opened up to the outside. The doorway through which he would walk for the last time in just a few minutes.

“Gear’s on the truck except this,” K9 continued, gesturing to the pile of battle rattle belonging to the boss. “Convoy’s all geared up and ready to roll. Killroy, Cooter, and I will be going with you as far as the green zone to set up logistics for the swap-out. We’ll come back on the supply bird tomorrow if they can get airborne. Otherwise, another convoy is scheduled to COP Grant in a few days and the guys here can come pick us up there.” All he got in acknowledgment was a nod.

“SPC Maples,” Jim started, extending his hand for a handshake.

“Everyone here just calls me Mutt, sir,” he interrupted. “It makes it easier.”

“Alright, Mutt, got a minute to show me around?”

“Not much to show, sir,” Mutt offered by way of explanation. “You seen pretty much everything already walking across the vehicle yard. We do pretty much everything here in the ready room and some of the hooches. Follow me, and I’ll show you yours. Some of the team are already unloading your gear into it. They built up the buildings about a month ago and took down the tents, so there’s at least that… the tents were a real bitch. Didn’t even try to keep the sand out, not to mention the scorpions.”

Mutt turned to go out the door with his new boss in tow, but didn’t make it far.

“Have a plan to kill everyone you meet,” Jim said aloud as he read the hand-painted four inch tall blazing red letters above the door.

“Borrowed that one from Mad Dog Mattis,” Mutt explained proudly. “Not sure who actually painted it though. Used to have a sign when we were in tents, but pretty sure one of the Red Horse team building the palace here lifted it when we weren’t lookin.”

“Seems a little harsh,” Jim said mostly to himself, but loudly enough Mutt felt the need to explain further.

“Nah,” he said with a shrug as he shouldered through the door into the blistering heat and blinding sun, “we steal stuff from them all the time. I guess it was only fair.”

Jim peeled his eyes away from the door. How many times had he crossed under those words, rifle in hand and weighed down with gear, on his way to pick through and analyze the shattered remnants of someone else’s life. It’s funny, he thought to himself, how quickly the people whose things he picked over became something less than human. They were objectives. One objective led to three or four more. Those objectives, dealt with according to custom, generally led to more. That’s how the game was played. Played on a giant chess board that used to be a large province. Played only with pawns, and under control of kings and queens who were far from the action.

Jim stood and walked over to where a large laminated map was hanging from some nails driven into the plywood walls. This map had been pristine when he had first hung it here. Now it was almost completely covered in red or black exes, many of them clustered closely together in a few hot-spots. It didn’t look much like a chessboard, but then again, the rules they played by didn’t look much like chess.

“You got a bunch of them, didn’t you?” CW2 Lowry, Warlock’s replacement, said quietly. He had come in unnoticed and was standing just behind and slightly to his right.

Lowry, who went by Cooter, had come in early when Warwick had been evacuated. He was originally scheduled to come in with a complete team to replace the COP’s veterans in just under a month. The powers that be, noticing the high success rate of this small outpost, opted to use the excuse to enable a longer hand-off period and sent the new team lead in early.

“Doesn’t matter, though, does it Cooter?”

“What do you mean? You took down all those bad guys. That matters,” Cooter said trying to sound encouraging.

“Yes. I suppose it does,” Jim said tiredly, “but I’m pretty sure we created almost as many as we got rid of. Maybe more. Such a waste.”

“They keep makin ’em, we’ll keep takin ’em,” Cooter said, trying to be helpful. He had only arrived on station a month ago, and didn’t seem to understand what Jim meant.

“I’m glad you understand it that way. The team needs that,” Jim said with a sense of finality in is voice.

“They told me the other day that your replacement washed out of training. Got hurt.”


“I was planning on having a few months at least for you to train me. Now I lose even that,” Cooter said sorrowfully.

Jim struggled within himself to keep from telling the new guy how selfish and irrelevant that point was given the circumstances. It’s not like things here had turned out like he’d planned. In fact, if he’d been given the choice of going home under the current conditions or staying here, he’d have stayed here until hell froze over. He made a conscious effort to unclench his fists and stretched out his arm, placing the tip of his index finger on a single red ex piled on top of four black ones. “This was the first,” he said, but didn’t say more.

Warwick had the newly printed and laminated map spread on the table in front of them. On the map were a series of grease pencil marks indicating both the objective and planned ingress and egress routes.

“Another team over in Ramadi id’d this one a few hours ago. They called in saying it promised to be honey hole,” Warwick said with a grin.

“Don’t get too excited Warlock,” Jim said, struggling to suppress a yawn. He’d only fallen asleep an hour ago, and the mission wasn’t real enough yet for adrenaline to compensate. “Do we know anything else about it?”

“Not much, sir. The area has been pretty quiet. Word from Brigade is that patrols have only encountered the occasional pot-shot. Should be a pretty good place to get your feet wet.”

“You worried about me?”

“Sir, no offense, sir,” Warwick said bluntly, “but you’ve already got three strikes against you. First, you’re not an operator. I’ve never seen one of your type who couldn’t get into serious trouble when surrounded by a squad of my brothers.”

“Your team is anything but ordinary from what I understand, and I know enough to not let my ego get in the way of you doing your job. I’m here to take advantage of what your team can provide… not to run your team.”

“You might not actively try, but it’ll take time for you to make good on that promise. Besides, you’re still a Major,” he said somewhat apologetically and with a hint of warning in his voice. “Second,” Warlock continued, “you’re intel. There ain’t any desks or power point slides out where we go.”

Jim grimaced, but didn’t say anything.

“And third, you’re Air Force. If the Army does a bad job training management for this kind of work, I have serious doubts about anyone else doing better. Three weeks of pre-deployment training ain’t going to count for squat out here.”

Jim wanted to be angry, but this was exactly the kind of open feedback he’d told Warwick he expected. Experienced operators like him tended to overlook many of the traditional customs and courtesies in favor of avoiding an untimely death, and it wouldn’t really change anything to tell him the training had been more like six months when all was said and done. It didn’t hurt his decision calculus that his survival depended pretty directly on Warwick. A flat “thanks for the vote of confidence,” was all the reply Jim offered.

“Well, sir, keep your eyes open, mouth shut, and ears tuned-in when we’re outside the wire and you’ll do fine. Should we call in the crew and get ’em spun up?”

“Yeah. We need to get on this one before word gets out and the cleanup crew arrives.”

Warwick stepped out of the ready room to rally everyone, leaving him alone with his thoughts. Warwick was crusty. He’d been here four months for this tour, and already had four other tours in this god-forsaken country under his belt. He knew what he was doing, and had long ago lost the ability to be political or polite when it came to getting a job done and coming out alive. There was no way to misinterpret anything that ever crossed his mind or lips. He knew Warwick meant what he said in the kindest possible way, but it stung a little to admit that he was almost certainly the biggest liability on the mission.

Aside from the quick tour by Mutt, he hadn’t had much time with any of the team other than Warwick who seemed somewhat irritated at having to relinquish his position – especially to an outsider. That said, Warwick had dutifully handed over the reigns and provided an exhaustive in-brief earlier in the day. He couldn’t help but wonder how many of the anxious looks he had been intercepting from the team, especially the more experienced ones, were due to their distrust of how he would handle himself in a firefight. Moments later, Warwick returned with the full team who all circled the map, focusing intensely on the objective and instantly beginning their individual analysis of the situation as Warwick briefed them on the details.

Jim shook himself, blinking his eyes hard to pull his focus free, and looked wearily at the pile of dirty body armor and other battle rattle on the table. He wasn’t all that convinced it would be worth the work to button up. Would it be all that bad, he thought to himself, to just get it over with quickly if something went wrong?

He checked himself. He’d told himself over and over again not to let those kinds of thoughts creep back into his mind, but his success rate seemed to strongly favor his unseen opponent. It was a tenacious beast that had been growing stronger for a while now, and had made a habit of rearing its unwelcome and ugly head more and more frequently.

He picked up the plate carrier and held it out at arms-length from him. It’s familiar smell made him nauseous. Months of sweat, sand, dust, dirt, blood, and all the other contaminants endemic to a destroyed city in a war zone permeated everything in spite of vigorous attempts to clean it all off. No matter how hard he scrubbed, some of the stains were still there, visible or not. All the scrubbing had done was to wear the fabric covers threadbare in spots. A few in particular seemed to have been indelibly marked against any means of removal.

“Wolfpack one, wolfpack two,” the radio crackled in his ear. It had felt like an eternity since they had gone in. Hearing Warlock call him without having heard gunfire was an inexpressible relief. It meant they had been a nasty surprise rather than encountering one.

“One,” he answered tersely.

“Objective secure. Come work your magic.”

“Copy. Headed in.”

“All clear, sir,” the gunner in the turret called down. “Entrance is three meters, right side. Can’t miss it.”

Jim grabbed his rifle and ducked out of the truck with two more of his team and an interpreter close behind, leaving the drivers and gunners in the four trucks behind in case the team needed to make a hasty egress. Somewhere just out of sight there were half a dozen of his men who had been the first out of the trucks when they had halted. He couldn’t see any of them, but was infinitely glad they were there.

The door to the building, what was left of it at least, was leaning haphazardly against the shattered door jamb. Apparently the breaching team had opted for shaped charges on the hinges and latch instead of just kicking it in. As he looked at the splintered wood, he couldn’t help but wonder if it had even been locked. This thought didn’t last long, however. There was a mission to accomplish, and it had nothing to do with the door. He entered the small dark space, scanning it through the still uncomfortable green glow of night vision goggles. It was empty except for his two protectors. He stepped forward into the darkness, but a dull pain in his chest made him realize he had been holding his breath. He consciously started to take a slow, deep, breath, but the pungent residue of explosives hanging in the air seemed to sear his lungs and triggered an involuntary cough.

“Don’t worry about that sir. You’ll get used to it,” the young soldier in front of him said as he deliberately worked his way forward into a long narrow hallway, checking each connected room as he went. “I kinda like it now. Smells like work.”

“Don’t listen to him, sir,” countered the other soldier keeping watch behind them as they moved forward, “Monkey just likes blowing stuff up. I still hate that smell.”

“I’ll take your word for it,” Jim grunted. He didn’t like having to search through the labyrinth of rooms in this unusually large building, it was making him uncomfortable. He keyed the mic on his radio, “Wolfpack two, wolfpack one.”


“We’re in, but don’t see you,”

“Last door, up the stairs. Building’s clear.”


The three moved swiftly to where the rest of the team was waiting. A dim light from an infra-red glow-stick cast grotesque shadows into the corners and over the faces of everyone there. The entry team was spread around the room with two watching out the windows, two watching the door, and two more towering over a collection of hooded and flexi-cuffed people.

“Warlock, can we get some light in here?” he asked. Watching the world through NVGs was disorienting, and with the combination of anxiety and sleep deprivation he was near enough to puking without adding anything else. They needed to come off.

“Monkey, find a light,” Warwick commanded.

A moment later the light from a single bare and dim light bulb completely washed out his NVGs. He flipped them up out of the way and scanned the room with his natural eyes. He wouldn’t have believed it possible, but the green scene in his NVGs was less disturbing than the shadows and darkness he saw all around him. Against one wall was a low table stacked with a jumble of large plastic containers and seemingly random scientific equipment. Against the opposite wall were a number of sleeping mats with blankets randomly scattered around. Apparently the captives had been asleep prior to the team’s arrival – just like planned. Other than these features, the room was barren.

There was nothing hanging from the mud brick walls. Nothing covering the rough planking of the floor. Nothing but the single light bulb hanging from the ceiling. For the life of him, he couldn’t figure out what the place had originally been intended for. Perhaps some kind of apartment building, or maybe a feeble attempt at an office building back before the city had descended into chaos. Whatever it had been, it wasn’t that anymore. Like everything else he had seen, it had first been stripped of anything useful, then co-opted into the fight.

Jim moved over to the chemistry set and poured over its contents. It was just a simple IED factory. Nothing sexy. The intel must have been over-played. The smell of diesel and nitrate fertilizer hanging in the air was all the evidence he needed to know what this crew had been up to.

“Grab everything with wires that isn’t already attached to a container. Leave those ones to Warlock,” Jim commanded. “Keep your eyes peeled for shaped charges, or even plain copper discs. Anything paper goes too. Keep your gloves on, and bag everything so we don’t lose any finger prints.”

“What about all the chemicals?” Gomer asked.

“Just fuel and fertilizer. Nothing to worry about unless we get stupid, and not much we’ll learn about them we can’t get from the photos.” Jim paused here and thought for a moment.

“Monkey,” he continued, “this place needs to have an industrial accident when we leave. We can’t haul all this crap with us, and we can’t leave it here. Make sure the place is empty and torch it off.”

Immediately, two of the team started photographing the workbench and methodically collecting the items he had asked for, while Monkey went down to the trucks to collect what he needed for the fireworks show.

“Alright, let’s see who our little chemists are,” Jim said to nobody in particular. He moved to the nearest one and pulled off the hood. A pair of terrified looking brown eyes looked back up at him. She couldn’t have been more than twelve. Maybe fourteen if she was of the petite persuasion.

The interpreter stepped to Jim’s shoulder, ready to be of use.

“Ask her what clan,” Jim commanded. The interpreter complied, and Jim stood silently watching while the translator worked.

“She says she was brought here from Yemen as a laborer, and that she doesn’t know anyone locally. She says the ties binding her hands are hurting badly begs you to loosen them.”

“Go ahead and loosen them,” Jim said. The interpreter immediately moved to comply.

Warwick, who had been working over the chemistry set, stopped what he was doing, turned, and just managed to bark a loud “Sir!” when the girl leaped up with a knife in hand that she had apparently been hiding under her long black dress. She lunged at Jim, but Gomer, who had been down on one knee a few feet away inspecting what looked like a remote-control module, turned instinctively when Warlock shouted, raised his rifle, and released a three round burst. At least one of the rounds caught the girl in the back just below the last rib on her left side. It exploded out of her right side just below the breast, leaving a gaping hole and splattering both the wall and Jim with bits of blood and lung. She dropped the knife and collapsed on the floor within a foot of Jim’s feet. Bright pink foam was starting to leak from the corners of her mouth and from the exit wound as she tried to speak.

“She prays,” the interpreter said matter-of-factly, wrinkling his nose at the smell of fresh blood that was beginning to mingle with the smell of burnt gunpowder. All Jim heard was the ringing in his ears and the beating of his heart, but he understood what the interpreter meant.

“What the fuck did you do that for?” Warwick screamed loud enough that it pierced through the ringing. A stream of uninterrupted profanity and reprimands for being an incompetent desk pilot son of a bitch officer filled most of the next several minutes while the rest of the team methodically identified and photographed the rest of the prisoners and collected evidence. “The next time you even think about risking my team like that Gomer’ll let the little whore cut you! Nobody here is innocent! You get that! NOBODY! We find a six year old kid in a place like this, they’re a killer no different than Haji Abdulla, and we treat them accordingly.”

“The old man is laughing again,” Gomer said to himself, but loud enough that Jim heard. It didn’t make any sense. Neither he nor Warwick were laughing, and there weren’t any men over twenty among the captives.

Jim looked down at those brown eyes as they rolled uncontrolled in the young woman’s head. Most of her internal organs had been devastated by the tumbling bullet, but it still took several minutes before she stopped struggling to breathe. The metallic taste of blood filled his mouth and nose, and he could feel the progress of a drip of sticky hot liquid as gravity slowly pulled it down his forehead. The nausea got the better of him, and he involuntarily puked all over the dying girl.

Jim retched as he pulled on the vest. It had been an involuntary part of the routine for months, and he couldn’t wait to turn the awful equipment back in to supply and be rid of it forever. Thankfully, nothing came up; a consequence of his not having eaten that morning or even the night before. He wasn’t going to go back into the world of men covered in vomit.

He plopped the Kevlar bucket on his head and adjusted the magazine holders and other gear. All told, the load added up to almost sixty pounds, and it had felt oppressively heavy when he first arrived here. However, it was just a matter of course now, and felt about like a heavy blanket draped over him. About the only part of him that registered the weight were a few bulging discs in his back, and he had gotten good at ignoring them with the help of large doses of Ibuprofen. The doctors would probably give him a hard time at his next physical, and his kidneys might never work the same again, but at least he had been able to function.

As he finished the ritual buttoning up, he felt an irrational desire to burn every piece of clothing and equipment he had on. He wanted to watch the flames purify it of all that had been absorbed from this putrid place. But the rules were the rules. He had to wear it for the convoy and turn in everything but the uniforms at his home station. He would definitely burn the uniforms though.

Albuquerque has its Good Points

The brown sort of desert that is Albuquerque isn’t my favorite environment. I miss trees and brush that are even slightly green, and I could happily go the rest of my life without ever running into a cholla cactus again. That said, new Mexico has it’s charms. One of them is quick access to the trails in the Sandia foothills, some of which are within a mile of my front door. The last two Saturday’s in a row, Michael and I have hiked one of them to a large granite formation that looks almost like a dam. This last Saturday, Liz came with.

Access to daylight is important to my well being in the winter, so hikes like this are something of a lifeline.

Michael packed a carrot for his snack. It was 20 degrees when we left, but by the time we stopped and were in the sun it was quite comfortable.
An accidental picture… so flattering. I think I was trying to look at the picture of michael eating his carrot. Anyway, it does show the ridiculously blue skies we get here. That and the amazing sunsets are two of the best things about New Mexico.

It is kind of funny hiking the foothills though. You can hear the dull roar of the city while being completely in the wilderness. That is a little hard to get used to.

TDCS Controller Step 5 – Making Electrodes

I’ve finished the updated design for my TDCS controller, but I’m waiting for a few parts that I didn’t have on-hand and couldn’t strip off of the board that represented my first attempt. Rather than just sit around and wait, I decided to figure out how to make a decent set of electrodes without ordering stuff online.

I used a standard 3.2mm mono-jack to connect the leads, and had intended to build my own cables. However, I don’t have any wire around the house that is suitable for this use. All of it is either way to heavy a gauge, or it’s solid core and stiff. I can either wait for the parts to arrive, or I can improvise. If you know much about me, you know I’m fond of improvising so long as it isn’t unsound. I had a cable from a pair of headphones laying around, and the only difference between a mono jack and stereo headphones is an extra conductor that I can completely ignore.

Headphone wire is well enough for the cable, but breaking out pigtails requires slightly more robust stuff. Again, I didn’t have any wire laying around that was suitable, but I did have an old DC motor I scavenged years ago, and the power leads to it were just right. I clipped those off, soldered and heat-shrinked (is that a word?) them, and soldered on some alligator clips. To make the actual electrodes, I cut two pieces of 14ga solid copper wire (taken from some extra ROMEX wire I had laying around) and coiled it into about a one inch disc.

Stage one of my electrodes for TDCS. The copper coils are 14ga copper from wiring leftover after building a barn out back several years ago.

From what I’ve read, the electrodes can burn you if the current isn’t distributed over a large enough area. Standard practice is to use saline soaked sponges, so I went to the local WalMart to see what was available. All of the sponges I could find in the cleaning isles contained an antimicrobial substance (you can tell because it warns you against use in aquariums). I don’t like the idea of that kind of stuff migrating from the sponge into my head, even though that’s a mostly irrational concern. I kept looking for a sponge that didn’t have that stuff in it. The make-up isle had the answer.

Make-up sponges don’t have antimicrobial stuff on them except for some vitamin E. They are also about the right size. I bought a bag for a dollar and headed home. Using a utility knife, I sliced a pocket inside two of them and inserted the wire coils. After soaking them in salt water, I stacked the two on top of each other and connected them to my first controller design (it generates the right current, it just doesn’t show you it’s working and the safety features won’t work right). The controller reliably produced the correct current through the pads.

To make it easier to distinguish anode from cathode, and to keep the whole thing together, I made small pouches out of red and dark blue material to stick the sponge and electrodes in. While I was rummaging through my wife’s sowing kit, I also grabbed some elastic and velcro to make some bands to hold the pouches in place. Here’s the end result

The electrode sponges fit inside the pouches. Red for Anode, black/dark blue for cathode. I was somewhat limited by the range of fabrics in Liz’s scrap pile. Dampened with saline, the sponge/pouch combination lets plenty of current flow.
I sewed velcro onto a few bands of elastic (no comments on my sewing skills… I’m an engineer, not a seamstress). Two for the head, one for the arm.

Now… I just need those parts to arrive and I can test it. If all goes well, the last step will be to design or buy an enclosure. I haven’t decided yet if I’ll have a friend 3-D print one, or just buy one from the electronics hobby type stores.

TDCS Controller Step 4 – Redesign

An unfortunate outcome of many first attempts is the learning that goes along with failure. My initial design for a TDCS controller had some weaknesses (okay… outright failures). At first, I attempted to fix them on-board by cutting traces and soldering wires to re-route power, or by dead-bugging extra components onto it. However, you can only do so much without having to shift gears and start over. This post is all about the redesign.

The driving force behind the re-design was my inability to make the TSC888 current sensing amplifier work like I wanted. However, I can accomplish the same thing with a simple op-amp. In fact, the LM358 that I used as a voltage comparator can work pretty well, and I have a few extras of those around. The trick with using this kind of set-up is to either reference the current sense voltage to ground, or to build up a differential amplifier. The simplest method I could think of was to put the current sense resistor in the circuit after the load and make it the last component the current flows through on its way towards ground.

The basic current regulator is unchanged. It worked so well, I can’t come up with a reason to change it. With R2 at 68ohms, the regulator (U1) is hard-wired to produce 1mA. When S2 connects iwth R1, the effective feedback resistance generated by connecting R1 and R2 in parallel is 34ohms and results in a 2mA current.

The LM334MX is set for either 1mA or 2mA depending on the position of switch S2

The nature of the LM358 calls for another change. It can have an offset voltage between inputs of several milivolts. With a 10ohm sense resistor like I had in the previous design, each milivolt of offset represents a 10% error at 1mA of current. However, increasing the sense resistor to 100ohms increases the sense voltage by a factor of 10, so a 1mV offset would only represent a 1% error. That’s good enough for me. Adding an extra 100ohms of resistance into the circuit shouldn’t really be an issue for my application.

With a 100ohm sense resistor (R3), I need a gain of 10 to produce 1V output per miliamp. Configuring an LM358 (U3A) for a gain very near 10 with a 91K (R10) and 10K (R9) resistors will replace the TSC888, and do so in a package that is easier to solder. I also added a 1uf capacitor (C1) to the output lead to absorb any transients that might inadvertently trigger the crowbar. I also added a 2.2K output resistor (R14) feeding another 1uf capacitor (C2). The resistor capacitor combination gives a 2.2ms time constant, so it will take about 10ms (5 RC time-constants) to react to changes in the output. This will help to further damp out any transients, but do so quick enough that a failure that result in a relatively high current won’t injure anyone.

R3 is in series with the load resistance (i.e. my head ultimately). The current flows out of the regulator (U1), out through the load resistance, and through R3 to ground. C1 is there to dampen transients at power-up. The LM358 amplifies the voltage by a factor of 10.1 thanks to the feedback resistors (R9 and R10) to produce an output of 1.01V/ma on pin1. R14 and C2 form an additional dampener against transients.

In order to determine if the output current is above 5mA, I can use an op-amp to compare the output of U3A with a 5V reference. However, that means I need a stable reference voltage. Since the supply voltage can vary from about 9V to 24V, I can’t use it directly. I could use a regulator like an LM7805, but there will be very little current drawn from that source so that would be overkill. Instead, I used a simple 2.2K resistor (R8) and 4.8V zener diode (D3) to derive the reference. The 4.8V zener blocks current until the voltage across it reaches the zener voltage (4.8V), at which point it lets current flow. R8 limits the current that can flow through the diode so it doesn’t melt once it starts conducting. I originally wanted a 5V reference, but the 4.8V zener was substantially cheaper than the 5V option and was close enough to meet my needs.

The 5V reference source is derived from a 4.8V zener diode (D3) and a 2.2K resistor (R8)

As before, I used an LM358MX op-amp for the voltage comparator. Each device comes with two op-amps in the package, including the one I used for the current sense amplifier. Ultimately, I need just one more amplifier to sense an over-current condition and trigger the crowbar, but I would also like some status indicators. Since the LM358MX is relatively inexpensive (and I have several extra available) I decided to add another one to the circuit.

The crowbar driver (U4B) is very simple. The inverting input (pin 6) is tied to the 5V reference and the current sense output is tied to the non-inverting input (pin 5). When pin 5 is less than pin six, the output on pin 7 stays low (ground). However, if the output from the current sense circuit exceeds the reference voltage (approximately 4.8mA), the output on pin 7 rises to the supply voltage and triggers the SCR (U2). U2 then latches on and shunts the supply to ground. Once that happens, the fuse (F1) opens up and cuts off power to the whole circuit.

Pin 5 of U4B is tied to the current sense amplifier. A 1V signal on pin five corresponds to a 1mA current through the load. If the current exceeds 5mA, the output of U4B goes high and triggers the SCR (U2), blowing the fuse and cutting power.

For convenience, I want two indicators: one to show when the 2mA setting has been selected, and one to show when the circuit can’t supply at least 1mA. The circuit for status indicators (LEDs) is similar to the crowbar driver, but I use a voltage divider (two resistors) off of the 5V reference to set the threshold voltage. I could have gotten rid of the indicator LEDs, and used one amplifier to run both the crow-bar and for current sensing, but they are cheap and easy to work with, so I opted to add another chip. The voltage divider on U3B set by R11 and R12 set a 1.4V reference on pin 6. If the output of the current sense circuit is above 1.4V (1.4mA output), pin 7 goes high and LED1 turns on. The divider on pin3 of U4A sets a 0.84V refrence. If the current sense voltage drops below 0.84V because the load resistance is too high (like when it’s disconnected) or because the battery has dropped too low, pin 1 goes high and turns on the red LED in LED2 (not shown). R5 and R13 limit the current through the LEDs to keep them from burning out.

U4A lights up the red half of LED2 when the current sense voltage drops below 0.84V to indicate a continuity problem or a low battery. U3B lights up LED1 when the current sense voltage is above 1.4V to indicate the 2mA output is active.

The final change I made from the previous attempt was to add diodes in line with the battery and power jack. If you’re only going to ever run this thing off of one or the other power source, there isn’t a need for the diodes, but if you happen to have a 9V battery plugged in and you connect a 12V power supply, you’ll end up with current flowing from the power supply into the battery. That can result in some nasty stuff. The opposite condition can occur if the battery voltage is higher than the power supply voltage. Two cheap diodes (D1 and D2) are all it takes to prevent that possible outcome.

D1 and D2 prevent current from backflowing if both a battery and power supply happen to be connected. F1 is a 100mA resetable fuse.

So, putting it all together, here’s the end result:

Copyright by Peter Johnson, February 2019 and released under the terms of the Gnu General Public License (GPL). This design comes with no warranty whatsoever, express or implied, for any purpose. It is provided for educational purposes only. Send recommended improvements or polite inquiries to Peter@diligent5.org.

With the new design comes a new board layout (slightly larger, but easier to fabricate at home). The mask sheet containing the photomasks for both the photoresist and the solder mask can be downloaded here. The capacitors are Panasonic outline B, diodes are SOD-123 packaged, resistors are 0804 size, LED1 is 0804 and LED2 is a custom two-color LED footprint. The ICs are all SO8 packaged. The process I use for fabricating boards is described here if you want to try making one for yourself. The .brd and .sch files for Eagle Cad can be downloaded here.

I had to order a few extra parts with the redesign, and am waiting for them to arrive. Once they do, I’ll test the resulting circuit and post the results. Until then, if you make improvements or just decide to build your own, I’d love to hear about it. Leave me a comment below.

The almost completed board. There are a few resistors, capacitors, and diodes that are still on order, and I need to connect the switches. The two vias in the center of the board are reserved for connecting an optional panel-mount voltmeter to display the current.

TDCS Controller Step 3 – Testing the Design

In previous posts, I described the process I went through to design and fabricate a circuit designed to safely apply 1mA of current to any load (including potentially a human). Up to this point, things had gone well. The TSC888 amplifier intended to measure the actual current flowing turned out to be a little small for hand-soldering, but my practiced and patient hands managed it okay. I wouldn’t recommend it to someone who is just starting out with surface mount components though.

With the board built, I plugged in a 9V wall-wart transformer, connected a 1K resistor to substitute as a human, and switched it on. The LED blinked, then turned off. A little probing revealed that the fuse had been tripped. connecting my oscilloscope to a few test points and cycling the power switch revealed that the crowbar was working beautifully except for the fact that it was tripping due to power on transients. In an effort to continue evaluating the rest of the circuit, I added 1uf capacitors to the output of the TSC888 and to the input pin on the SCR. They are the blue cans visible in the picture below.

After the boards are cut out, I solder on the components. Surface mounts can be hard to deal with if you haven’t done them before. First, solder flux is your friend. It can help stick the components in place, and makes the solder flow well. Second, a dental pick in your non-dominant hand can help pin the part against the board while you tack it down with the soldering iron. Get some solder on the tip of the iron and use that. Drag the solder across the fluxed pins and the solder should flow pretty evenly. If you get too much and short out pins, solder wick is an easy way to clean it up. I’d also keep some chip-quick around for removing components that didn’t go on like you thought they would or that let the smoke genie out.

With the capacitors in place, the low setting seemed to work well. I measured 10mV across the 10ohm sense resistor, so the current source was working as designed. I switched the board to the 2mA setting, and so far so good. To test the ability of the regulator to handle extreme cases, I shorted the output leads together, and the low-current error light turned on. Weird… With the leads shorted, the current should be the same or higher than if the leads were disconnected. After a little fumbling and scratching my head, I realized what I had done wrong.

Consistent with most of the application notes and examples in the datasheet, I tied the power supply pin of the TSC888 to the output of the current regulator. This works fine when the load resistance (your body resistance) is relatively high, but when the resistance is low, the output voltage from the regulator drops very low to keep the current constant, and the TSC888 starts to behave erratically. It quits working all together if the connection is shorted because there is no power to drive its amplifiers, and that’s exactly when I want it to work the most. I had to pull off the chip, cut a trace, and tie the power supply pin (pin 5) to the input supply voltage (Vcc). A perfect example of why chip-quick is helpful… I know of no other way to reliably remove a surface mount component without destroying it (and often the board traces) in the process.

The output regulator worked perfectly everywhere from short-circuit to 10K ohms. If I didn’t care about monitoring or safety features, I’d be good to go. However, as I turned up the resistance, there came a point where the output of the TSC888 would drop out. Current would still be flowing, but the indication output would be 0V. I again connected my scope and dug in. Apparently the TSC888 is cutting of after a brief period. It’s unexplainable behavior. It could be because I damaged the IC by getting it too hot while soldering-removing-resoldering it, but if that’s the case, I should probably find something less sensitive. Otherwise, there is some “feature” I didn’t account for, and that part isn’t suited for my application in the first place.

The yellow trace is the indicated current flow. It turns on like it should, but then shuts off a very short while later. The actual current flow continues. The power supply line and sensing lines are clean and within specs, so I’m at a loss as to what causes this.

So. To summarize… After all that work, I have to go back and redesign. The core building blocks all work, but there are definitely things to change:

  1. Add a diode in line with the battery terminal and power jack to prevent current backflow if someone connects external power while a battery is installed.
  2. Add filter capacitors to the crowbar signal to suppress transients that erroneously trigger a shutdown.
  3. Move the 10ohm current sense resistor to the load low-side and build my own op-amp detector to sense current flow instead of the TSC888. If I use another LM358, I can use the remaining op-amp to drive an indicator for whether 1mA or 2mA is flowing.

More to follow. I’ll redesign the circuit, build another board, and come back when I have something to report.

TDCS Controller Step 2 – Building The Circuit Board

In the previous post, I described a circuit design for a TDCS controller I’m developing. Because I’m working almost exclusively with surface mount components, I can’t really breadboard the circuit. The best option I have is to build a circuit board and use that for testing. Conceptually, I could send the board out to a fab shop and have them produce one. However, doing a 1-off build, especially when the design hasn’t been proven, is expensive, risky, and takes a while. Because I’m impatient and like to do things myself, I make my own. In this post, I’ll describe the process I use for making my own boards.

If you happen to be interested in trying this yourself, you’ll need a few things:

  1. A circuit board layout
  2. Dry-film photo resist
  3. Double-sided copper-clad circuit board(s)
  4. 300-400 grit sandpaper
  5. Printable transparencies (ink-jet printable in my case)
  6. A good quality printer
  7. A laminator
  8. A laminator pouch that has been through the laminator
  9. Latex gloves
  10. Washing soda (sodium carbonate)
  11. Copper Etchant (I use ferric chloride)
  12. UV curable solder mask
  13. A UV light source (a black-light works well)
  14. A rotary tool (Dremel) and carbide bits
  15. A hacksaw to cut out the finished board
  16. Soldering Iron and solder

I make my boards by laminating bare copper clad board with dry film photoresist. I then print the pattern negative onto an inkjet printable transparency to use as a photomask while exposing the photoresist. To make the mask, I use Eagle CAD to build the board layout as part of the circuit design. However, I don’t like the way Eagle exports the graphics. I turn off all the layers but pads, vias, and either top or bottom layers and export the result as a PNG at 1200 dpi. However, the exported graphic isn’t quite ready for exposing a board. First, it isn’t black and white. In order for the photomask to work right, it needs to be either transparent (white) or black. Second, with the latest version of Eagle the signal names are printed on the traces and need to go away. Finally, the drill-holes are almost filled, and it’s much easier to hand-drill if the etched copper acts as a sort of pilot hole to guide the drill.

Using Gimp and a round brush I erase (paint over in black) anything that blocks the drill holes. Then I use the threshold tool to turn it to black and white. Once that is done, I mirror-image the bottom layer and add any graphics (like my logo) and text I want or have room for. In the end, anything black in the image will be areas where the copper is etched away.

To build the mask for curing the solder mask, I turn off all the layers in eagle except either the tStop or bStop layers, change the fill pattern to a solid color, and export it using the same settings as the board layout. Using Gimp, I use the threshold tool to make it black and white, then invert it so that the pad areas are black (black areas won’t cure and can be wiped off when the mask is applied).

Printable transparencies are kind of expensive, so I try to cram as much onto each one as I can. To do this, I use Scribus to lay out a full page that includes all the masks I need. A calculator and the properties dialog box are handy to make sure the relative geometries of tiled masks are the same. Finally, I use Scribus to export the result as a PDF for printing. Generally, I’ll print out a sheet on copy paper and make sure things line up, and that device footprints match the components I have on-hand. Make sure you don’t have “shrink to fit” selected on the printing options, and when you print the actual mask, set the print quality to maximum and resolution to at least 600dpi.

Printed mask sheet. The top right is the top of the board, bottom left the bottom, and the right side are the respective solder mask patterns for the top and bottom.

To laminate the dry-film photoresist onto the copper-clad board, I start by using 320-grit sandpaper to sand off oxidation and contamination from the board. I’ve tried using brillo pads and cleanser, but have had issues with the film not adhering strong enough and pulling loose at inopportune times. Once the copper has been sanded bright, I clean it off with acetone to make sure I didn’t leave any oils on it. I also wear cheap latex gloves from Harbor Freight any time I handle the board to make sure I don’t get skin oils on it.

Once the board is clean, I cut a piece of film about 1″ wider and longer than the board I want to laminate. I also cut a piece of card stock about 2″ longer and wider than the board. The dry-film photoresist is protected by a thin sheet of plastic on both the top and bottom, and one of these protective sheets needs to be removed in order for the film to work. To separate it, I sandwich the corner edge of the film between two pieces of scotch tape (sticky-side to sticky-side) and peel the tape apart. One side of the protective film will peel away (usually the inner side based on the way it wants to curve). If it doesn’t, try again, maybe on a different corner.

Stick tape to each side of the film and pull it apart to start separating the protective plastic from the film. Usually the film on the inside of the curl will pull away. Only pull the plastic off one side of the film at this point.

I then tape the top-edge of the film face-down (protective layer up) on the card stock. I align the board underneath the film and feed the film into a hot laminator taped-end first. The laminator will grab the paper and begin pulling it through. Gently lift up on the film to keep gentle tension on it and avoid bubbles or wrinkles as it feeds into the laminator. Once it’s been through, I usually run it through two or three more times just to make sure it’s good and stuck. At this point, the film around the edge of the board is laminated to the cardstock, so I cut around the board with a utility knife to get the board free. Then, I turn the board over and repeat the process for the bottom.

Tape one edge of the film (film side down) to a piece of card-stock. The card-stock helps pull the board through the laminator, taping the film to the paper makes it easy to put a little tension on the film to avoid bubbles and creases.
Run the cardstock-board-film combo through a laminator set for it’s hottest setting. Put gentle tension on the film as the board is fed through the laminator to prevent bubbles and creases in the film. I usually run it through the laminator 3-4 times in a row. To laminate film on the bottom of the board, flip the board over and repeat.
When the board comes out of the laminator, it’ll be stuck to the paper. Use a utility knife to cut around the edges of the board to release it.

To align the top and bottom masks I cut them out, leaving about a 1/2″ margin around the pattern, and use a piece of left-over circuit board to act as a spacer between them. I tape one of the masks to the piece of board, then flip it over and tape the other mask down so that it’s aligned. It isn’t exact, but it’s about as good a way as I’ve found for consistency. When I’m ready to expose the board being etched, I slide it between the masks, and sandwich it between two pieces of glass that I took out of a thrift-store picture frame. Rubber bands, binder clips, or clothespins work pretty well to keep it all together (you have to flip it over without messing with the alignment, so it’s important to get at least some tension on it).

I’ve seen lots of folks on the web double-layering their masks to get stronger contrast, but in my experience this is totally unnecessary, and can make it really hard to work with small features. It’s almost impossible to get them exactly aligned, and variances in the printer can make it absolutely impossible. Using a single layer mask I’ve reliably made boards with traces down to about 10mils (1/100th of an inch) that turned out crisp. However, I do prefer to keep all the clearances and trace widths 15 mils or larger just to make it easier on myself.

I tape the mask to a section of scrap PCB to keep the separation right and hold them aligned with each other. The photoresist under the black areas will wash away when developed, leaving exposed copper which will be etched away by the etchant solution.
I sandwich the mask and board between two thin sheets of glass I took out of a thrift-store picture frame to keep the mask tight against the board. The rubber bands keep the whole thing together so I can flip it over and expose the back side without changing the alignment.

The photoresist is sensitive to UV light (and to a lesser degree it’s sensitive to the blue-end of visible). Some people have had success using fluorescent lights a few inches above the board, but that didn’t work particularly well for me. Others use sunlight, but I like to be able to work when it’s dark or cloudy outside, and the UV from the sun can vary widely based on time of day and cloud conditions. My solution was a 13W black-light LED bulb I bought at Lowes or Home Depot. I rigged up a fixture that holds it about 4 inches above the board. In this configuration, a 5 minute exposure is about right. Your mileage may vary, and you’ll likely have to experiment with different exposure times to get consistent results. Take good notes and it won’t take long to make beautiful boards.

To expose the board, I put it about 4-5 inches below a 13W LED black light I bought at Lowes. 5 minutes exposure seems to be just about right with this geometry. After five minutes, I flip the board over and do it again on the back side.
After the exposure is done, you should be able to see the pattern in the photo resist. It may seem a little blurry, but seems to sharpen up when developed.

To develop the photoresist, carefully peel off the protective plastic. Use tape on the corner and lift up if you can’t get it with your fingers. Be very careful and gentle, pulling the plastic outward and upward to avoid tearing the film. This is one point where you find out if your board was totally clean and if the laminator was hot enough. If the photoresist starts to peel off, clean it off with acetone or a long bath in hot water and washing soda and start over. Assuming the plastic comes off cleanly, drop the board in some luke-warm water with washing soda* dissolved in it. It isn’t critical how much. I usually use about a teaspoon or two per cup of water. If the water is too hot, you may end up washing away both the developed and undeveloped portions and have to start over

*you can find washing soda in the laundry isle of most grocery stores, or you can make your own by heating baking soda in the oven at 350F for half an hour or so.

To develop the photoresist, drop the board into a solution of washing soda and luke-warm water. Agitate it gently, and gently rub it with a soft-bristled toothbrush to work the softened mask loose. Be very gentle or you may damage the finer features.

Gently agitate the board, and lightly rub it with a paintbrush or soft toothbrush (I used cheap acid brushes from the plubming section at Harbor Freight). The unexposed areas will soften and gradually wash away. Keep going until all the copper you want to etch away is completely exposed. You can patch up areas that are accidentally exposed by drawing over them with a sharpie after the board has dried off and before etching, but I prefer to just re-do the exposure since it turns out much neater that way. When all the copper you want etched away is exposed, rinse the board in cold water to stop the developer from eating away the film you want to keep. Let the board dry before you try to re-touch any copper that got accidentally exposed.

The developed board should have sharp lines and good contrast. If anything isn’t right, start over. Once you start etching, it’s really hard to fix things that aren’t right.

At this point, the board is ready to etch. At the moment, I’m using Ferric Chloride etchant, but you can find tutorials on the web for making your own etchant from hydrogen peroxide and hydrochloric acid (muriatic acid for cleaning swimming pools) you can buy at WalMart. Pour some etchant into a non-reactive container and swish the board around. The board will etch faster if the etchant is warm. Also be careful with FeCl… it indelibly stains almost everything it touches, especially clothes, skin and counter tops. Definitely use gloves, and lay down some paper towels or cardboard to protect your work surface. Check the board every few seconds. Quit when all the exposed copper has been eaten away and rinse the board with plenty of warm water. Don’t dispose of this stuff down the drain, the copper in it will kill aquatic life. I’m currently looking for a good chemist to show me how to precipitate the copper out of the solution so I can neutralize the remainder and flush it down the drain. Until then, I pour the etchant back in its original container and keep it.

The exposed copper with start to turn pink, and the etchant will begin darkening as copper is dissolved into it. Swish it back and forth gently. How long it takes to etch will depend on the strength and temperature of the etchant. When you think it’s done, rinse the board with water and look closely to be certain. If there is any copper that still needs to be etched away, put it back in the solution for a while longer.
At this point the etching is done, and the board has been rinsed off. There are two real options for removing the film. The quickest is a brief soak in acetone. The other is to throw it back in the washing soda solution overnight.

Depending on how impatient you are, and what you have available to you, a short soak in acetone will quickly loosen up the photoresist. I don’t really like working with harsh organic solvents like acetone, so I usually just drop the board into a solution of hot water and washing soda and leave it overnight.

The same solution used to develop the photoresist can be sued to take it off if you are patient. If not, hot water speeds up the process, or a quick dip in acetone will do the job.

If you are working only with through-hole components, you can stop after the film has come off, drill the holes with a dremmel or drill press, and start building the board. However, I prefer surface mount components, and those are much easier to work with if you apply solder mask. Besides, solder mask makes the board look better (even if you screw it up a little like I tend to). The soldermask I use is a UV curable epoxy paint that is heat resistant enough that it won’t blister when you solder components to the board. It’s available online from places like ebay and Amazon. To make it work, you need a thin layer, so I squeeze a small amount of the paint onto the board, then squeegee it under a sheet of transparent plastic (I use a laminator pouch that has been through the laninator). The biggest problem I’ve had is getting the paint too thick so the UV light doesn’t penetrate far enough to cure the deeper layers. Spread it out THIN. I’ve also found that taping one edge of the transparency to a piece of cardstock will help minimize the sheet or board slipping with respect to each other (not shown in the pictures).

Make sure the board is really clean and dry, set the board on a piece of card-stock or other disposable surface, then put a small blob of the solder-mask compound on the board. Put a piece of plastic trimmed to a little larger than the board over the paint (I use a laminator pouch that has been through the laminator because old-fashioned transparencies are hard to come by these days).
Use a flat surface (in this case a nylon kitchen scraper) to spread the compound out thinly and evenly. My biggest problems with producing good looking boards come from the paint being too thick and the UV light not making it all the way to the bottom and curing that portion of it. Make sure there aren’t any bubbles, and scrape extra paint out the edges and onto the paper.

Once you have a thin layer of paint, expose it using the same setup as was used to expose the photoresist. Five minutes seems about right with my setup, but you’ll likely need to experiment on some scrap boards to get it right. Don’t experiment on large areas. There is no way to peel off the stuff once it’s cured. It’s tough as nails. After exposing it, lift the clear plastic and wipe the board with a clean paper towel to expose the component pads and vias. Wipe it thoroughly. I’ve used an acetone dampened paper towel before, but you run the risk of blistering incompletely cured paint. Once the pads are clean and bright copper, put the board back under the light for another ten or so minutes to make sure it’s fully cured.

Place the board under the black light (with it turned off), align the mask on the board, and place one of the pieces of glass on it to hold it in place. About 5 minutes seems to be about right using the same setup as I did for exposing the dry film photoresist.

After wiping off the uncured paint, I put it back under the light for 10 or so minutes to make sure it’s good and cured. Once the paint is dry, I use a dremmel with bits I got on amazon to drill out the vias and through-hole components. Finally, I cut the board out. A hack-saw works okay, and band-saw works better (I don’t have one of those yet). A dremmel with a cut-off wheel will work in a pinch (what I used here).

You can see the blistered solder mask on the corner of the board on the left. I’m pretty sure it’s a matter of the paint being too thick, or the curing time being too short combined with the fact I used acetone to help wipe off the pads..

At this point, the board is ready to build up. Solder on the components according to the schematic and fire it up to test. Soldering surface mount components is an art form of its own, but the short version involves using plenty of flux paste, dental picks to hold things in place, and solder wick to suck up extra solder when you get too much. Be careful not to overheat the components. If things aren’t going as planed, stop and let things cool off.

After the boards are cut out, I solder on the components. Surface mounts can be hard to deal with if you haven’t done them before. First, solder flux is your friend. It can help stick the components in place, and makes the solder flow well. Second, a dental pick in your non-dominant hand can help pin the part against the board while you tack it down with the soldering iron. Get some solder on the tip of the iron and use that. Drag the solder across the fluxed pins and the solder should flow pretty evenly. If you get too much and short out pins, solder wick is an easy way to clean it up. I’d also keep some chip-quick around for removing components that didn’t go on like you thought they would or that let the smoke genie out.

There you have it. That’s how I build prototype circuit boards. Now it’s time to test it.

TDCS Controller Step 1 – Design

NOTE: This was an initial design, that evolved as I built and tested it. For the final design, complete with a description of each major component, see this post.

The fundamental building block for any TDCS controller is a current source capable of supplying between one and two milliamps of current through the human body. This can be a bit of a challenge because the resistance of the body varies with electrode placement, skin resistance (which can vary from one second to the next), body composition, and a bunch of other factors. The trick is to build a regulated current source capable of automatically adjusting the output voltage to get the desired current even with this rapid and unpredictable change in the person being exposed.

Digging through a pile of data sheets, I found a perfect solution already packaged and ready for integration. The LM334 current regulated source can be programmed to provide a constant current ranging from microamps to ten milliamps. All it takes it is a simple resistor to set the current. Two small and cheap parts are all that’s required for the basic circuit.

We’re I comfortable that nothing would ever go wrong, and didn’t want any feedback about what the thing is doing, that would be it. I could build one on a dime, and do it for just a few dollars. However, I’ve spent way too much time fixing electronics and have seen too many cases where the primary failure was a shorted out semiconductor to trust a piece of silicon to not short out. In fact, I made a good living in college taking advantage of that particular failure mode. If the regulator failed, there would be nothing to prevent a comparatively high current from flowing through my brain and doing significant damage. Clearly this thing needs a few more features.

First, I like the idea of being able to select a lower current setting. Most of the research I’ve seen uses either one or two milliamps, and I’d like to be able to use those two settings at least. I could pretty easily build in an adjustable resistor, but they are much more expensive than simple resistors, and I’ve not seen anything showing an advantage to being able to finely tune the output. Instead, I built in a switch and an extra resistor.

Pin 4 on the LM334 is the input power, and can be from 1 to 40V. The feedback resistance between the four output pins (R1 and R2) sets the output current.

Rather than switch R1 and R2 in and out of the circuit completely and deal with the undefined state that happens during the switch transition, I hard wired R2 into the circuit and selected it to produce a 1mA output. When the switch is closed, R1 is added in parallel with R2, cutting the effective resistance in half, and subsequently doubling the output current to 2mA. If the regulator doesn’t fail, the current won’t ever be anything other than 1mA or 2mA. A simple flip of a switch will seamlessly change the output between only these two values.

With that aspect of the design complete, the next step is to provide an indicator that the thing is on. It’s a simple matter of adding a resistor and an LED on the power line. The maximum voltage the regulator can handle is 40V, so I selected a resistor value that would limit the current to about 15mA or less through the LED at that input voltage. Lower voltages will still light the indicator, but it just won’t be as bright. For my purposes, that’s okay.

The LED is actually half of a two-color (red/green) led. When power is applied, the green LED will light up.

The last three things I want in the design can be incorporated with a single basic feature. I’d like some indication when current isn’t flowing, be able to monitor exactly how much current is actually flowing, and a safety feature to shut the thing down if the regulator fails for any reason. To do any and all of these things, I need to be able to monitor exactly how much current is actually flowing through the body.

It can be a little difficult to measure low currents without disturbing the system. Initially, I believed the pile of data sheets had a ready made answer. The TSC888CILT is designed to measure the voltage across a shunt resistor and provide a gain factor to make measurements easy. Combined with a 10 ohm precision resistor, the chip puts out a 1V/mA signal.

With a 0.1% Resistor on R3, and a gain of 100 built into the TSC888, the output on pin 1 comes out to a round 1V/mA so a simple panel-mount voltmeter can be used to monitor the current.

With a signal to monitor the output current I can do several things. First, and most importantly, I want the device to shut off completely if something goes wrong and current rises above a safety threshold. If the output current exceeds 5mA something has gone wrong, and 5mA is well below the damage threshold for tissue. The simple answer for circuit protection would be to put a fuse in the line. However, mA-range fuses are hard to find, are bulky, and may not react fast enough to satisfy me. On top of that, I’m not particularly keen on replacing fuses if I happen to accidentally short something out while testing. This is where the current sense signal comes in handy.

It’s pretty easy to set up an op-amp as a voltage comparator and use it to trigger a “crowbar” if the output current exceeds a set value. The idea of a crowbar is that it’s like dropping a metal crowbar across two electrical terminals to blow a fuse or trip a circuit breaker. With the 1V/mA sensing gain and a 5mA threshold current, all that is required is a 5V reference voltage on the inverting input and the current sense signal on the non-inverting input. For the reference voltage I used a simple zener diode and resistor. I also used a 4.8V zener because it was cheaper than the 5V ones available at the time, and because 4.8 mA is still high enough that I want to shut things down if the current goes that high.

U5 and R8 combine to form a constant 5V reference. If the voltage on pin 5 of IC1 exceeds this reference, the output of pin 7 goes to the positive supply rail. The other op-amp in IC1 is used as a threshold detector to turn on the red LED of U3 if the output current is below approximately 0.8mA. The voltage divider of R7 and R6 set the threshold voltage based on the 5V reference.

The output of the comparator then needs to drive the crowbar. I added a resetable fuse just after the power switch. This fuse is guaranteed to hold 100mA (plenty to run everything) and trigger before something like 250mA. The MCR08B Thyristor can handle 800mA, so it will happily load the fuse when triggered. The output of the voltage comparator will trigger U4, which will turn on and stay conducting until power is removed. When the SCR turns on, the resetable fuse opens up and cuts power until power is totally disconnected and the fuse cools. Theoretically, none of this part of the circuit should ever actually function, but I’m happier knowing it’s there. If the current regulator fails, the crowbar will shut things down without putting anyone in danger.

U2 is a 100mA resetable fuse which is tripped by U4 if the output current of the device goes above the safety threshold. This is a redundant safety feature to ensure that a short in IC2 (the current regulator) won’t expose anyone to dangerous currents.

Because the chip I used for the crowbar trigger has two op-amps, I have one to spare that I can use as a fault detector. If the output current falls bellow 1mA, either the electrodes are disconnected, the connections are poor (i.e. they are too dry), the battery is low, or something else is wrong. R6 and R7 form a voltage divider off of the 4.8v reference used for the crowbar, and sets an 840mV reference for the voltage comparator. Any time the output current falls below 0.84mA, the output of the op-amp goes high and turns the red LED on.

The last parts to add are jacks for power and to connect the output leads. I used a simple mono-headphone jack for the output, and a 2.1mm barrel jack for the input power. I also added a connector and a diode to make it so I can plug in a 9V battery instead of a wall-wart transformer. When connected to a human, you should run this thing on a battery all the time to make sure you don’t encounter any ground-loop issues. At a minimum, make sure that the output of your power supply is floating with respect to earth ground (if you don’t know what that means, use a battery). There are good reasons hospitals have outlets with the neutral floating with respect to the ground pin. Finally, I added some mounting holes to the diagram so they show up on the board.

All combined, the circuit looks like this:

The completed TDCS controller circuit with a 1mA/2mA current regulated source, a 1V/mA monitoring circuit, power and fault-indicator LEDs, and a safety crowbar to shut things down if something goes wrong. VDD is for powering a panel-mount digital volt meter hooked to TP1 to display the output current (optional), but I didn’t include that in the schematic.

I laid the board out in such a way that I can reliably make my own by using 15mil clearances between traces, and 20mil minimum traces. I could have made it much smaller if I were going to farm this board out to a fab house by putting components on both sides of the board, using small vias, and finer traces. However, I like rolling my own boards, so traces are pretty thick, all the components are on the top-side, and vias are large enough I can drill them, stick a wire through it, and solder it to both sides. The final board is just under 2″ on the long side.

Top board layout. The bottom board is almost all ground-plane with a few jumpers and pads for vias and through-hole components.

Now, on to making the board.