Turret Board Revision 2

I received my turret boards from OSHPark. Here are OSHPark's generated images of the PCB.





I immediately set to soldering enough components to test the 3.5v power output from the voltage regulator. But ... after soldering on some capacitors, resistors, the regulator, and a JST connector, I had no power. I double-checked the schematic and saw that I completely screwed-up the power connection to the voltage regulator. I cut a trace with an X-acto and soldered a jumper and hooked it back up. I had very little power coming from the voltage regulator and it was quickly too hot to touch. I unplugged it before I melted something.

I'll have to go back to the schematic to determine why my jumper did not fix the power issue. I knew that I would have to perform multiple revisions but I'm disappointed to screw-up a board with such a basic mistake. I did not label my nets hardly on the schematic and I might have caught the issue if I had. My schematic for the main board is better labeled and I hope it does not suffer from such a basic mistake.

I tested the camera footprint and it fits mostly okay except the holes for the two plastic studs are mis-aligned. The holes for the metal tabs, though, work perfectly, even though they were kinda a guess. So I think that I will have this footprint perfect for the next revision, though I do think I would like to try a break-off board. This will allow me to place the camera pretty much wherever I want, instead of being forced to remain on the backside of the turret board. I can just run a 6-wire ribbon cable from the breakoff to the turret board. One potential issue: I do not know how much leeway I have, in terms of distance between the oscillator and the camera.

Something else I belatedly figured-out: The IR send library is hard-coded to use Arduino pin 3, because it relies on one of the ATMega's timers. In my main-board design (which has already been sent to OSHPark), I have the turret-motor Hall sensor connected to that pin. I did this because I wanted sensor on that fast-spinning motor to be connected to a hardware interrupt. Anyway, it should be easy to reroute the wiring so that the IR transmitter is connected to pin 3. I might just forgo the turret encoder when I hook-up this revision (this is assuming I can even run Blink on my first attempt at an ATMega standalone board).  Another mistake I realized I made before even I have received this board: I used inline resistors on the Hall-effect sensor lines, instead of pull-ups.

I've been playing with transistors to turn-off the IR beacon when the IR transmit is active (see last post), though I haven't determined whether it actually helps, since I do manage to transmit/receive signals when there is an IR light active, without the addition of this switch-off circuit.

Immediate to do for next version of turret board:
- Revise camera footprint and move it to a section of the board that can be broken-off
- Fix power circuit
- (potentially) add IR beacon turn-off circuit
- Add transistor to drive IR transmit LED, as it can use more current than the ATMega pin supplies

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