Dual PCB problem


I thought with 2 5v PCBs you could use both at the same time without any issues while not needing a toggle switch to only feed power to 1 at a time, but I just tried wiring both together and anything that is wired to both is automatically set to on without even holding the button/direction down. I’m using an agetec pcb with a saitek p150 and I get this problem. Am I forgetting to do something or is it just required to use a toggle switch no matter what?


Thats a bit of a mistake. No, you dont HAVE to have a toggle switch or diodes, but its recommended so you dont fry anything if you leave it plugged into two systems at the same time.

BUT, no matter what, no matter which PCB is actually being used, no matter what protection you put in to protect the systems (or none in your case) BOTH need to be powered. So if you’re not going to bother with the toggle switch or diodes, then connect the +5 on both PCB’s with a piece of wire. Your description of the problem is exactly what you should expect if only one of the PCB’s is getting power. Power them both and you’ll be fine.

The golden rule of multiple PCBs are that they ALL must be powered for any of them to work.


Ok I understand what you meant by both must be powered at the same time now. Didn’t really understand what the issue was before because I’ve plugged both pcbs in before and had no issues, but now I see what would cause the issue is if the 5v from each pcb are wired together then both were plugged in at the same time. It’d really be some really random occurance to have both a DC and PC near each other and plugging in both systems at the same time, but I guess you can never be too safe. If I got diodes, what kind of diode do I get for this and where would I end up wiring them inbetween? Thanks for the help Toodles.


shut up jake


(power from DC cable)----|>|----+-----|<|------(power from USB cable)
 (DC PCB)-----------------------+-----------------(USB PCB)

Just about any kind diode should work. In both cases, the end of the diode with the stripe goes to the PCB’s, the end without the stripe goes to the power from one of the cables.

Really, before bothering with this, you should connect the +5 lines with wire and test that they work at all before adding diodes into the mix


From the looks of that diagram, I am going to have to clip the power wires and put the diode inbetween. That’s pretty much the major reason why I didn’t want to use a toggle switch in the first place because I don’t want to clip the power wires of my pcbs. Well I suppose just using diodes means I don’t have to drill a hole for the toggle switch, but is there any way you know of to get around clipping the +5v wire? Guessing not, oh well. I’ll deal with it.