I’m working on a project where I want to control the speed of a fan using a microprocessor.
I read several posts about using an Arduino Uno to control the PWM function on a 4 pin fan you find in PCs, and as I had the parts lying around I thought it would be a good place to start.
The fan is a Foxconn brushless 12V DC 0.6A – model number PVA080G12H-P01
My power supply is a 12V DC 1000mA probably from an old 3COM switch – model number 3c16741a
The supply has a barrel connector that fits the Uno so I thought this would work out perfectly.
I know the correct way to wire it would be to connect the fan’s power directly to the supply’s output and only have one control wire to the Uno, but as I was only at the ideas stage I didn’t want to hack into the cable just yet. The Vin on the Uno can handle 1A, so I thought for an initial test I would be fine to use the GND and Vin on the Uno to power the fan.
Briefly turning the supply on made the fan turn very fast, as expected. The Uno survived but there was a distinct electrical smell from the fan. It’s likely the fan has never been used before, and almost certainly not at unlimited speed, so I thought it would be fine to move on and work on the PWM side.
I used the code by dlloyd here https://forum.arduino.cc/index.php?topic=415167.0 and connected the fan’s control pin to the Uno’s 3 pin. Powering it over USB, it ran perfectly at three speeds for 5 seconds each, although at a low overall speed due to the limited voltage. I modified the code to add 0% and 100% tests, unplugged the USB cable and plugged in the 12V supply. The fan behaved erratically, spinning up, clicking, and slowing down randomly, before quickly going “pop” and stopped working all together. Connecting it directly to the supply does nothing so it’s definitely dead. The Uno continues to fun fine.
Due to the smell in my simple test, I’m assuming just connecting the fan to the supply would have resulted in the same death, but everything I’ve read suggests connecting a 0.6A 12V fan to a 1A 12V supply should be fine. Can anyone explain how it could have happened so I don’t make the same mistake again?