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I have looked around here and on the Raspberry Pi forum, but I cannot find a conclusive answer to my question. Is there a max voltage I should allow to go through the GND pins on a Raspberry Pi header? I would like to attach a 5 volt I2C port expander and a 7-segment display (through the I2C expander). Can I safely connect the common-cathode of the LED's to the Raspberry Pi's GND pins?

TO clarify, can I attach the ground pin (such as on a led or a microchip) to the raspberry pi's GND pin if that circuit is operating at 5 volts. I am not directly shorting the pins.

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    You cannot allow voltage "to go through the GND pin" or indeed any pin on any computer. Voltage only exists between 2 points. You need to ask a sensible question with more detail of what you are trying to do. – Milliways Feb 20 '17 at 22:49
  • @Milliways Updated my question to make it clear. I am not shorting pins, but I want to have a 5V led's negative side go into a ground pin. – user173724 Feb 21 '17 at 3:18
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The supply (+5v) and ground in your project are likely shared between all components. Between the Pi, an I2C expander and some 7 segment displays you'll be fine connecting all the +5v together and all the grounds together.

As @Milliways says, there is no concept of a max voltage you can connect to a ground pin. I think you are confusing things with how much current a (GPIO) pin can sink or source

For the supply pins (+ and -) there is no real limit to the current you can use other than :

  1. The limits of what your power supply (batteries, mains, charger etc) can provide
  2. The gauge of wire you are using for connecting them (draw too much current through thin wires and they'll begin to melt)

NOTE: if you are using a +5v I2C expander you do need to check/verify the I2C pin voltages - as the Pi SDA and CLK work at 3.3v levels, and you might need to use a level shifter...

  • Thanks. I'm not worried about i2c. The pi can handle it according to everything I have read. – user173724 Feb 21 '17 at 14:11

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