Two power systems, reading voltage off both without magic smoke.

Projects General Guidance
1

Hello and thanks in advance for any advice you can give!

I'm building a little remote controlled webcam + RC car project and would like to monitor the levels of two power systems. The first is a 5v USB power pack running the Raspberry Pi (which is in turn running the Arduino, wireless and camera) and servo, then a 9.6v RC battery pack running the wheel motor.

I think I have things mostly nailed down, I just have a couple of questions to make sure I don't blow anything up. :slight_smile:

Question 1: Will tying the ground of both power systems together cause any system destroying issues? From what I've read it should be that way or the voltage readings to the Arduino will be wonky.

Question 2: Should I be slapping a diode from ground to the voltage reading analog inputs for protection?

*edit: oops, re-uploaded a smaller image, my bad. :wink:

RCElectronics.png
RCElectronics.png780×581 57.4 KB

2

urizen:
Question 1: Will tying the ground of both power systems together cause any system destroying issues?

No.

urizen:
Question 2: Should I be slapping a diode from ground to the voltage reading analog inputs for protection?

That would only provide protection against reverse voltage by shorting out the battery. The diode would then die, followed by the Arduino. A diode in series would protect against a reversed battery but it would offset any voltage reading by the voltage drop of the diode. Use a voltage dividers to get the voltages being read down to a safe voltage (typically 5V or less).

3

Awesome, thanks! I will make sure to leave some overhead on the dividers in case something freakish happens. :slight_smile: