Electronics beginner here. I have Raspberry Pi 4 GB variant. I have the following power requirements:

  1. power a 5V cooling fan 12V cooling fan (a spare cooler master)thanks @Milliways
  2. safely (i.e. avoiding both backcharging & over-volt/amp problems) power the board via GPIOs, I have to use OTG mode sometimes so I am not using the USB-C port for charging.

How can this be done in least cost?
Inspired by @tlfong01 comment on this question, I am thinking a buying a 24v SMPS and divide its power between 1 & 2, but I don't know how to practically do it.

OTOH I already have a good fan, should I buy heat sink also?

  • Your question is unclear. If you are using OTG there is no way to avoid "backcharging" unless you design your own circuitry. Save yourself a lot of angst (and money) by purchasing a 5V fan. A fan will do little without a heatsink. You only need a tiny fan (and maybe not even this) . See raspberrypi.org/blog/thermal-testing-raspberry-pi-4/#comments
    – Milliways
    Dec 1, 2019 at 9:55


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