This seems like a question that has been asked before, I couldn't find on the forum, or elsewhere, a fitting answer.
I am trying to measure V and A of a 12v battery using a shunt connected via a negative.
I already purchased and fitted a shunt (https://www.amazon.com/gp/product/B013PKYILS), and the schematics of the circuit is:
Note the 4 wires from the shunt that feed the monitor. I want to connect them in parallel to the rpi.
Do I need voltage dividers? Optoisolators? I also have 4 of these monitors. Do you think I can connect all 4 (each with 4 individual wires) to the rpi?
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The GPIO pins on a Pi (any Pi) are limited to 3.3v and 16mA. They are also all digital. What you probably need are a couple of AD converters, either with suitable output limits, or running through level shifters (and, probably, optoisolators).
The typical A to D converter used with a RPi has a range of several volts. No problem to use a resistor divider to reduce the battery voltage to match that. However the voltage dropped across the shunt will be much lower and may require special attention.
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