Computer Fan Sensor Wire
Posted: Wed Jul 18, 2018 8:18 pm
I have a kegerator that I have successfully managed to setup temperature monitoring using 3 temperature probes one in the fridge, one in the tap tower and one outside to monitor the room temp. I also have grafana installed on the pi that graph the temp over time and will send out email alerts when the fridge gets either to warm or too cold. I have 2 80 mm computer fans hooked up 1 to circulate the air and the other as a tower cooler. They both have 3 wires. The yellow wire is currently not hooked up. Its my understanding that this yellow wire is used to determine fan state. My question is can I hook those yellow wires to the raspberry pi to tell if the fan is running. They are already running hooked up to a separate power supply so I am only concerned with the yellow wire. I know because these are 12v fans I can't just hook it up strait to the gpio. Could I drop the power down using a series of resistors perhaps 3.6 kΩ and 9.1 kΩ? I believe its called a voltage divider.