PWM Fans Question

[Hi P]

PWM Fans are the ones which speed can be controlled, right? and non-PWM are always running at 100%

 

Aside from noise, what are the advantages of PWM over non-PWM fans?

[IdiotPenguin]

I believe PWM is just another way to control fan speeds because I can control my 3 pin fans in the bios via voltage

[jakep0802]

14 minutes ago, Hi P said:

PWM Fans are the ones which speed can be controlled, right? and non-PWM are always running at 100%

 

Correct. As for the second question, I don't know too much about that.

[Jurrunio]

1. Yes

 

2. No. Those connected directly to the power supply with a molex connector will run 100% speed all the time, but those connected to motherboards that support DC mode in fan control can still adjust their speed.

[Kc7vwc]

This is flagged as answered, but a bit more:

Both methods allow for variable speed, but Pwm offers finer control, faster updating and smoother transition.

Voltage controlled fans tend to 'jump' right from one speed to another & have few 'steps' in-between. 800Rpm then straight to 1300rpm, for example, even if all you need is 1K Rpm.

Pwm will let you hit the exact speed you need, usually using 100-200 Rpm increments. 

[EsaT]

16 minutes ago, Kc7vwc said:

This is flagged as answered, but a bit more:

Both methods allow for variable speed, but Pwm offers finer control, faster updating and smoother transition.

Voltage controlled fans tend to 'jump' right from one speed to another & have few 'steps' in-between. 800Rpm then straight to 1300rpm, for example, even if all you need is 1K Rpm.

Pwm will let you hit the exact speed you need, usually using 100-200 Rpm increments. 

Actually there's no 100% guaranteed relation between PWM duty cycle and at what percentage of full speed PWM fan runs.

And minimum duty cycle or lower has even more varying range of results.

Those depend on manufacturer of fan.

And with more makers joining in it will get more varying.

 

And actual voltage control definitely makes fan speed scale very smoothly.

In SilentPCreview site and forum votlage control was used 15 years ago, before any of this PWM fashion.

Sure if your controller has only 1V steps then there are steps in speed, just like if there are steps in PWM duty cycle control.

Also speed not dropping at first might mean you having some dirty PWM chopper feeding fan square wave AC on top of DC offset.

Decade ago had such result with one of the fans I tested.

Don't remember if that fan was also one of those which started making electric squeeling/whining noise when fed such crap.