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

Another Project – TDCS Controller

CAVEAT: The design described here has fatal flaws. I’ve since re-designed it, and have left this here as a way to document the process and share the realities associated with designing even relatively simple things with whoever might read it. The current design is available here.

I don’t seem to be able to function well without some kind of project. Usually I have several waiting patiently for my attention. However, at the moment all my current ones require either time, money, or energy I just can’t afford to give. I have a coding project to finish the user interface for … Read the rest

Don’t Ask

How often do we casually ask someone we encounter how they are? Passing a casual acquaintance in the grocery store isle, the nearly universal greeting is to ask how they’re doing. Run into an old classmate you haven’t seen in a few decades who has their arms full of kids and is clearly on their way somewhere, and we ask how they’ve been. I know I’m guilty of it, and I’m pretty sure almost everyone else is too. This kind of callous or ignorant questioning needs to stop. We don’t really want to hear about our former classmate’s recent divorce … Read the rest

Grandpa’s House

When I was young my parents would take us over to my maternal grandfather’s house almost every Sunday evening. I have a great many memories of that house and the people in it.

My Grandfather’s house was a small pale-green concrete-block structure built shortly after World War II in Kearns, UT. As originally constructed, it had three bedrooms, two bathrooms, a small kitchen, a living room, a small family room, and not much else. I doubt it was much more than about 1200 square feet. Grandma and Grandpa occupied the master bedroom with its rather small attached bathroom. As you … Read the rest

Compromise

You say I block you from success,
That my needs cannot be met,
Without sacrificing what you need.

You have not listened to understand,
Nor given me time to teach,
What and why or discuss alternatives.

There is space in the ground between,
What you need and want aren't one,
Step back and then meet me in there.

We can do what needs doing together,
We can both find some room to withdraw,
And then forward together much stronger.


Quitter

I don’t have a lot of patience for quitters. I’ve spent so much of my life pushing hard through difficulty and frustration to accomplish whatever it was I was working towards that it irritates me deeply when someone (especially someone close to me) gives up on something that is ostensibly important. To some degree, giving up feels like a moral weakness or failure. Setting something aside for a while is one thing… An inevitable thing in mortal existence… An uncomfortable but bearable thing… An acceptable thing. Giving up with no intention to circle back and try again later is quite … Read the rest

Uncle John

My uncle John giving me my first salute as a Second Lieutenant

One of the core principles everyone who has ever gone through basic training will understand is that being invisible has it’s advantages. When your bus drives through the installation gate for the first time on your way to training, you develop a pit in your stomach and start to wonder just what you have gotten yourself into. As you watch others get chewed on, you try to shrink into oblivion and do everything you can not to get noticed. At least, that was my experience. No sooner had … Read the rest

Peter's Prose, Poetry, and Random Ramblings