So, it appears that after all my lofty proclamations about posting more often, somebody, as they say, thought they had a better idea. And it wasn’t me, honest. Well, maybe it was me just a little bit. Okay, 100%. Whatever.
Anyway, I have got the most delightfully tedious trivia for you. As I’ve mentioned, I’ve been tinkering with an old Mobile Armatron with the aim of putting it under autonomous computer control. I partially rewired the motors and built a small power supply for the eventual onboard logic, and then began on a motor controller that would fit in the Armatron’s "trunk space". I ordered a few L293 chips, since they seemed to be ideal for the purpose, and lots of people seemed to like them.
Unfortunately, I learned that setting up the circuit on a piece of protoboard would definitely not work. I ended up with a spaghetti nest of jumper wires that was so thick I couldn’t even fit them all in. Obviously, I’d have to design a board. I set that project aside for a while in order to do some reasearch on how to do that. I finally discovered three techniques which made it relatively easy.
One discovery is Eagle, a printed circuit design application, which makes designing boards easy (for limited values of easy.) You draw your schematic out in the schematic designer, choosing parts from a vast library and wiring them together. It is not a launch-it-and-go application. Eagle is quirky and odd and has a definite learning curve. I would definitely advise anybody to run through a few tutorials before trying to design a masterpiece. It took me a few hours, but I did get the hang of the basics.
The next discovery was of the toner-transfer resist method. Laser printer and copier toner can be transfered from paper to a copper-clad printed circuit board with the use of a simple clothes iron. Of course, using the correct sort of paper makes a big difference. It’s been said, and I must agree, that magazine paper works quite well.
The final piece of the puzzle was the cupric chloride etching method. A reusable etching fluid can be made by combing ingredients from both the drugstore and from the hardware store. And it works pretty well. I did notice that the etching process was pretty slow, but I eventually realized that was because it was a cold night. I had set my etching container in a Pyrex dish to catch any spills, so pouring hot water into the dish warmed the etchant and sped things along.
So, you may be wondering, what do I have to show for all that work? Well, it looks sort of like this: