Maximum safe PWM Fan frequency

petrzmax

Hi!

I'm setting my Duet Wifi 2 up, and I came to a problem with PWM fan. My fan doesn't like to run on low PWM frequency. I have set mine to 32kHz and now it is running fine from 1% to 100% of it's power. It's drawing about 160mA @ 12V at full speed. Should I change it because my mosfet can fail or it will run fine?

Maybe it's better to use lower frequency and some filtering circuit?

Best regards from Poland,
Artur

nhof

The mosfet normally switches in less than 100ns so it should be fine. 32khz is reasonable for that switching time.

Phaedrux

I get the best sound out of mine at 30000Hz and they've been running like that for well over a year no problem.

petrzmax

@nhof @Phaedrux Thank You guys for help. I read that it should be kept low around 500Hz, so I was worried about some hardware problems.

Best regards from Poland,
Artur

Veti

@petrzmax said in Maximum safe PWM Fan frequency:

. I read that it should be kept low around 500Hz

that is for non pwm fans as they might not work at higher frequencies

petrzmax

@veti My fan is Sunon EF50151B1 and it's not a PWM fan.

dc42

Using high PWM frequencies, you may find that the speed range is restricted. It's all very well saying you can go down to 1% in the M106 command, but that 1% might give you 70% of the full-power speed.

4-wire fans that use a separate PWM control signal are usually design for 25kHz PWM.

petrzmax

@dc42 That's true. I don't have full range speed control, but I prefer at least some control rather than not working fan. If there is some hardware solution to get this fan working at full range I will be more than grateful for some schematic etc.

Best regards from Poland,
Artur

For a fan "full range" is usually limited by the lowest voltage the fan will run and start at (mind you those specifications are without any static pressure from a fan duct). But even at the lowest speed it will be running a lot faster than 1% of full speed.

In this case 4.5V, so you could try to measure the voltage and pick the frequency that gives you the combination of a voltage close to 4.5V for the lowest setting and smooth running. Then you need to decide if you want 1% to be lowest possible speed, or if you want to approximate the % setting to % of RPM, say having 30% equal to 4.5V and the lowest possible speed.