Noisy DC motor with PWM

Projects General Guidance
1

Hello all,

I am using PWM to control the speed of a 12v DC fan. The fan emits an annoying whine when it is run at less than 100% (PWM 255) power. The fan is being powered through a SSR (IPS6021PbF).

Is there any way to reduce/eliminate this whining noise? :astonished:

TIA

2

Hi, you are probably hearing the PWM frequency.

Try changing the PWM frequency?: See http://arduino-info.wikispaces.com/Arduino-PWM-Frequency

3

Thanks for the tip Terry.

Should I try to increase the frequency? (The max for the SSR is 1.5khz.)

4

Pokey:
...Should I try to increase the frequency? (The max for the SSR is 1.5khz.)...

Hmm. Yes, increase the frequency, but 1.5 KHz may be worse than 500 Hz?

Let us know how it goes...

5

Yes you were right, the higher frequency was worse. The sound was louder and the pitch got higher—it was screaming! :astonished:

I took it all the way down to 12.5Hz, and now the sound is just a low hum. :slight_smile:

Thanks for your help.