Question about PWM fans

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lapoltba

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Dec 23, 2008
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So I understand how PWM fans work etc. etc.

Since PWM fans were designed to be compatible with this method of control, is it safe to assume that it will react nicely wne used with a controler that only has a 3 pin connector but uses PWM to control the speed of the fan?

To be more clear.
I will not be using the 4th pin on the fan connector (PWM Signal) and only the first three. (gnd, 12, rpm) So the internal circuitry in the fan that regulated the speed according to the PWM signal is not used. Will this fan run without the "growl" associated with non-PWM fans?

-Brian
 
lapoltba said:
So I understand how PWM fans work etc. etc.

Since PWM fans were designed to be compatible with this method of control, is it safe to assume that it will react nicely wne used with a controler that only has a 3 pin connector but uses PWM to control the speed of the fan?
Click to expand...
I would think so.
To be more clear.
I will not be using the 4th pin on the fan connector (PWM Signal) and only the first three. (gnd, 12, rpm) So the internal circuitry in the fan that regulated the speed according to the PWM signal is not used. Will this fan run without the "growl" associated with non-PWM fans?

-Brian
Click to expand...
It might depend as much on the controller as the fan.
 
Thats kinda what i was thinking.

I dont really know how the internals of the PWM fans are differnt from the others. IE. I dont know why they work better using PWM. If that is the case then I am probably right and they will work fine.

I plan on getting a Matrix Orbital or Crystalfontz controller. They both use microprocessors to create accurate PWM.
 
I have owned one PWM fan that without the signal on the 4th pin, defaulted to slowest speed, and I owned another fan that without the signal on the 4th pin defaulted to the hightest speed. If your fan defaults to the lowest and you use a fan controller, it would be real slow. For the fan that ran default slow, it was the stock 100mm fan on a CoolerMaster Hyper 6+ heatsink, and I remember at the time reading on forums that you could feed it a signal from a 5v source and it would cause the fan to run at 100%.

PWM fans are also designed to run at variable speeds with the same input voltage, where most fans are designed to run at full speed (and sometimes slowing them down will cause them to stall) or if they are the 3pin auto fan, they usually are resisting the voltage internaly, and the motor is designed to be able to run on a lower voltage.

So in your case, using a PWM controller to feed a PWM fan, if the fan runs 100% with no 4th pin PWM signal, then it is the same thing, your PWM controller will be pulsing 12V power to the fan.
 
I think the last line is exactly what i wanted to hear.

I guess i just didn't know if the pwm fans were quieter than the regular fans with PWM because of HARDWARE differences or if it was just because the PWM was doen onboard the fan. If that made sense...?


Thank you.
 
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