Tuesday, October 9, 2012

Target stand V2

I've made a new target stand. And a lot of errors... that I've since corrected.

The main error I've made is that I tried to violate one of the core rules of engineering: Don't build it if you can buy it. I tried to build a DC motor controller.

I was building a DC motor controller because this new target stand is powered by a DC motor. It has to turn both clockwise and counter clockwise. I already needed such a motor controller for my big moving table, so I figured I'd just finish making it.

So I built an H-Bridge. Initially it was able to show me +/- 5V when I asked it to. Perfect, works the first time! And it burnt out once I put it on a 12V power supply. Some internet searching and logic informed me that it turns out is suffered from something called 'shoot through'. This can be solved with the use of special H-bridge motor controllers.

I build a new motor controller on the perf board of the old one, and it didn't work at all. I build it on a proto-board and it didn't work. I tried two different kinds of H-bridge motor contollers and they didn't work. Maybe the old perf-board mosfets were more fried than I thought. Maybe the proto-board was broken from pushing parts that were too big into it. I don't have another day to waste on that. Fuck it.

Since this is a low power motor controller, I just bought one. I don't need a high power controller like the table will. They're like $6. What was I thinking?

Slap that shit together and now the table works, again powered by an arduino. At the end of the video you can see it fall apart, turns out I only put a single spot weld on the axle holder. The next day I painted that steel on thick and it works like a charm again.

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