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I have recently soldered a 90mm PC fan to a USB cable and it works great. I was wondering if it would be possible to power said fan off of the 5v output pin on the pico, and solder the black wire to ground. I would do it so I could run a script to power the fan on and off.

Sam Haydock
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2 Answers2

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Seeing as the Pico does not have a 5V output pin the answer is No.

The VBUS pin will have whatever voltage you put on it, which may be 5V if powered by USB and this depends on what it is connected to.

See https://raspberrypi.stackexchange.com/a/127865/8697

This will NOT control the fan and Pico GPIO pins are 3.3V low current.

Milliways
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  • Hello, Thanks a ton for the answer. Assuming the pico is powered off of 5v USB, would it power the fan. (off of the VBUS pin) If so, could it be programmed to turn on and off? Sorry if it is a stupid question I'm really new to this lol – Sam Haydock Jul 08 '21 at 02:50
  • @SamHaydock it depends on how much current the fan uses and how much whatever it is connected to can supply. I don't know what current the Pico would negotiate from a compliant USB source - I would assume 500mA as my iMac shows. You could control with a transistor, similar to the Pi, but there seems little point in a fan as the Pi doesn't need cooling – Milliways Jul 08 '21 at 03:08
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You can achieve what you want but not as you are suggesting. It does not matter if the fan is 5V 12V or 24V use a seperate power supply for it, do not power it with the Pi that is asking for destruction. Get yourself some MOSFETs or MOSFET modules that will turn on with 3V. The ones I use are opto coupled. With a MOSFET (N-Channel) connect the drain to the - or ground output of the power supply which is also connected to the ground of the Pi. Connect the + terminal of the fan to the + of the power supply, the - to the MOSFET drain. Now connect the gate to whatever port pin you want to use. When you turn that port pin on the MOSFET will turn on causing the drain to go to ground potential causing the fan to run. If you use the opto isolated switch you connect the (ground or 3V3 depending on how you want it to work) of the Pi to it and a Port pin. the other side of the isolated switch you connect the fan power supply and the fan there is no need to connect the grounds. This is based on the Pi's ability to sink or source current via its port pin. The connection is the same as a LED which the optocoupler input side is.

Gil
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