Legal Removal Request

Post: Using GPIO 17 to drive a relay via a transistor shouldn't cause any problems with the ADC DAC Pi, as long as the current being drawn from GPIO 17 isn't too high. I think the current limit on any GPIO pin is about 10mA so you just need a current limiting resistor in between the GPIO pin and the transistor to keep it below 10mA. Are you powering the relay from the 3.3V rail or from an external supply? The ADC DAC Pi uses the 3.3V rail as the voltage reference so any sudden large changes in the current draw on that rail could cause the voltage to drop which would in turn cause the ADC DAC Pi to give an incorrect reading. With relays, it is always a good idea to use a reverse protection diode across the coil so you don't get any negative voltage spikes on the power lines which could damage the raspberry pi. The main thing you have to check when you are using the ADC DAC Pi or any other ADC on the Raspberry Pi is you have a common ground between the Raspberry Pi and the battery you are measuring. If the grounds are at a different potential then that could cause problems with the values the ADC DAC Pi is reading.