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.