Disclaimer (can be skipped):
This seemed like the correct sub-forum for this question, please move it if I’m wrong. It also seems like noob question, and it sure is, but I haven’t found an answer to it. I didn’t look under every rock on the Internet, but I feel like the answer should be easier to find. For instance, none of these pages mention anything about the subject:
And make no mistake, I am a complete noob, even with electricity, let alone electronics or the Arduino.
Best to look at the rough circuit I made. It is not complete, but should give an idea of what’s going on. A FT232RL breakout, a Pro Mini and a shift register are involved. An appropriate external power supply can handle all those devices, but there are at least two issues.
If external power is disconnected and the breakout is connected to USB the breakout is powering everything! I’m not sure I’m reading the FT232RL datasheet correctly, but it looks like it can source a maximum of 50mA through its +V pins. Even if I misunderstood the specs the load could require much more current in this kind of circuit. Am I right in assuming this could be a problem and if so is the only solution to disconnect the rest of the project from VCC or even all Pro Mini pins while programming?
Is it an issue if both the USB to breakout and external power supply are connected at the same time? I know grounds should be connected, but I still can’t wrap my brain around what would happen if I basically power my circuit from two different supplies at the same time. They could even be at slightly different voltages! Is simply disconnecting the external power while programming and disconnecting USB while running enough? Assuming, of course, the 1st issue is solved.
That’s it for now, hopefully these are not too annoyingly dumb questions. Any help, tip or link appreciated! Especially about this whole ground connecting business and how it works with different power supplies, even with different voltages apparently!