I'm going to play around with moving heads running of a Falcon PiCap attached to a Pi 3B+. I won't be using it for pixels or any other functions other then running DMX moving heads off the cap for testing and my show. My question is, can I power the Pi and the Picap from a usb power supply such as the 5v 3amp ones you can buy in a shop or do I need to power it from a 5v or 12v power supply so that it can power the DMX on the picap?
If you set the PiCap for 5V power input, You should be able to plug the 3A power supply into the Pi and it will also power the PiCap. If you run into issues, you could save a little power on the PiCap by removing the large chip which is used to level shift the GPIO output voltage from 3.3V to the 5V needed for pixels, but I don't think you'll need to do that. Ditto for the RTC chip if you aren't using that.