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I just got an old PC fan from a computer that was taken apart at my school and I want to try and figure out how to make it turn on using the GPIO ports on a Raspberry Pi 3 Model B. It is a DC 12V fan and it has three wires. One red, one black, and one yellow. I looked it up online and it looks like the black is ground and the red is the 12V- wire. Is there any way I could control this straight from the GPIO pins. Thanks.

Edit: Is there a way that I can control the fan directly from the GPIO without a motor driver chip?

  • the fan is a motor ... google RPi control motor – jsotola Sep 27 '18 at 2:45
  • what do you mean by that? – rrr Sep 27 '18 at 2:47
  • the yellow wire could be used as a control line to control the fan speed or it could be a tachometer signal to read the fan speed .............. the fan voltage is probably printed on the fan itself – jsotola Sep 27 '18 at 2:54
  • yeah it is a dc 12v motor – rrr Sep 27 '18 at 2:56
  • I made an edit to the original question that might clarify my question. ^___^ – rrr Sep 27 '18 at 2:59
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There is no way to control safely any motor directly from a Pi GPIO. You always need to use a motor driver board or the equivalent in discrete components.

  1. The Pi GPIO are all 3V3.
  2. A Pi GPIO can only supply a few milliamps of power (say 20 milliamps).
  3. The back EMF generated by a collapsing motor field can destroy the GPIO and the Pi.

You can buy a suitable L9110S or L298N based board quite inexpensively from the likes of eBay.

You could use a discrete motor driver chip such as the L293D or for limited control (not direction) a ULN2803A.

You could implement your own circuitry with suitable transistors, resistors, and diodes.

  • The pins on a raspberry pi can be up to 5v though and it is right next to a gnd pin – rrr Sep 27 '18 at 14:48
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    @rrr Yes, you can power a small motor from the Pi's voltage rails. The motor will be running whenever the Pi is powered. That wouldn't be counted as motor control though. – joan Sep 27 '18 at 15:01
  • if i wanted it to be on whenever the pi was on could i attach the red wire to the 5V and the black wire to the ground pin and not use the signal wire? Would that be safe? – rrr Sep 27 '18 at 23:15
  • That would be fine (as long as the motor doesn't need more current than the Pi can supply, if it does the Pi will keep rebooting). – joan Sep 27 '18 at 23:21
  • it needs 12V but it should be able to run off of 5V right? It just wouldn't spin as fast? – rrr Sep 27 '18 at 23:33

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