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Topic: Running a 4-pin 12V Fan with a Potentiometer  (Read 1 time) previous topic - next topic


May 21, 2017, 09:28 pm Last Edit: May 21, 2017, 09:35 pm by mrskelital
Hi all, I'm stuck in a bit of a predicament.

I have a project that needs to be done by the 26/05/2017... Just 5 days away from the date writing this so fast replies would be much appreciated.

I am trying to run a 4-pin 12V PC Fan using an Arduino Nano, a Fairchild FQP30N06 N-channel MOSFET and a 10k OHM potentiometer; I'm using a 12V battery to power the fan.

However, I am very very new to this; I have no understanding of C and I have no idea about electronics; I'm a complete beginner. I have looked all over youtube and the internet but all guides for this seem to be non-noob friendly.

Would anybody be able to show me a noob friendly link or would anybody be able to give me a digram on how to wire it properly and how to program it? I want the potentiometer to change the speed of the fan as it is twisted.

I copied a simple circuit which was designed for a 2 pin DC-Motor but only the last couple of mm's of the twist would move the fan and it would move at a very slow speed; that was using the TACH pin on the fan as it would not work with the PWM pin.

Could anybody please teach me what I need to do?

Thank you all.


May 21, 2017, 11:07 pm Last Edit: May 21, 2017, 11:14 pm by Whandall
I think your problem is discussed in depth here: arduino-how-to-read-and-control-the-speed-of-a-12v-four-wire-fan.

You have a tachometer output and a pwm input from and to the fan.
Maybe the PWM has to be 12V... I only had a quick look at the link above.

PWM Control Input Signal
The following requirements are measured at the PWM (control) pin of the fan cable connector:
PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHz
Maximum voltage for logic low: VIL = 0.8 V
Absolute maximum current sourced: Imax = 5 mA (short circuit current)
Absolute maximum voltage level: VMax = 5.25 V (open circuit voltage)
4-Wire Pulse Width Modulation (PWM) Controlled Fans
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of. (D.Adams)


Thank you for the reply, I'll have a read into it!


May 22, 2017, 08:37 pm Last Edit: May 22, 2017, 09:16 pm by Whandall
This PWM frequency library can produce a 25 kHz PWM signal (tested on a Mega pin 11).

Code: [Select]
  Frequency: 25000 Hz
  Number of Possible Duties: 321
  Resolution: 8 bit
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of. (D.Adams)

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