Controlling 8x 12v 4 pin computerfans with arduino relay/mosfet?
Does this work, see photo? Would it be better to use a mosfet? I have 8 fans
4-pin fans already have all the needed electronics inside the fan (3-pin fans don't).
No extra parts needed.
4-pin fans should be controlled with ~25kHz PWM.
Plenty of examples on the net.
Google "Arduino 4-pin fan control".
Youtube video.
One Arduino PWM pin should be able to control eight fans (same RPM).
Leo..
I've got a one pin fan. What to do with it?
Ok, thanks. I saw the video. It looks simple. But what fan is telling the correct rpm? Or does it not matter? Can i put too much current into the fans if i wire them like in my diagram, but without the relay, but with them same 4pin to 4pin split cables, using only one pwm wire and one rpm wire to the arduino?
Measuring/displaying RPM is optional. Don't use tach of the fans(s) if you don't need it.
Otherwise use one of the eight fans for that, as reference. The others should spin about the same.
No, you can't put... Fans take the current they need.
Just connect all fans to the 12volt supply.
Connect ground of the 12volt supply to Arduino ground.
Connect all PWM control pins to the PWM pin of the Arduino
(they might already be joined by the splitter cable).
Maybe wise to experiment with just one fan, before connecting eight of them.
Most (not all) 4-pin fans have a minimum RPM, which is the same as ~20% PWM.
If you want to stop the fans, then you need that relay in the (+) line of the power supply.
Leo..
Ok, thanks!
Hi,
Do you need to control the fan speed?
What is the application?
Thanks.. Tom... 
Its just goint to be temperature regulated, I think. Its better if I can run it on lower speeds for durability, but if it doesnt get cooler I can run on max speed for a while.
Hi,
What are you regulating the temperature of?
It may be easier to run, 1, 2, 3, or 4 fans to regulate flow.
Thanks.. Tom...
Eight fans at low speed might be quieter than a few on high speed.
Leo..
watching that tutorial on youtube wawa recommended makes it look easy to controll eight fans with pwm. I just need to figure out how to use the temperature sensor, but that I have to do anyways. I was thinking about using the i2c temperature controller you can see in the picture, from adafruite. Do you recommend anything else
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