Tapestry

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: Convoy

Previous – Part 1: Packing Up

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 … Read the rest

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 … Read the rest

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, … Read the rest

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 … Read the rest

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 … Read the rest

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 … Read the rest

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 … Read the rest

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 … Read the rest