Sunday, April 10, 2016

The Lamp Matrix v1

So I got my lamp matrix PCB design manufactured from Dirt Cheap Boards:
After some messing around with the programming, it actually seemed to work:

I couldn't really get the light bright enough when they were strobing as fast as they could.  But then I noticed some oddities.  My TIP107's were heating up a lot.  Still not exactly sure why.  Then this happened:

Also notice the slight modification I had to make to that ULN2803 chip - had to bend the com leg out.  Poor design on my part.   You may not have realised yet, but I don't actually know what i'm doing.  A lot of trial and error goes into this.

So trying to pump 5+ amps through a tiny little trace like that turns out not to be such a good idea.  I needed to re-engineer.  Since i didn't want to wait for new boards to be manufactured and didn't want to have to re-solder all those components.

This seems to work a lot better.  The puzzling thing is that my TIP107's still heat up significantly.  The current draw also steadily increases as they heat.  Still haven't worked that one out.  Since each globe is 0.25a and there are max 8 ever on at once, surely the max draw of this would only be 2a.  This is the case when permanently on, but when it strobes fast (say 74khz), the draw goes up.  I have a feeling i may not be using the tip107's properly, so I need to go back to the drawing board for that.  Still, progress has been made!

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