PWM Fan Speed Control Audible Noise

hello, i make project to control PC fan by temperature,then temperature increase fan speed going higher then temp goes down fan speed goes down , but i have problem fan making noise something like "BZZZ". I'm using 10k ohm thermistor to read temp and 12v fan. Can somebody help me make it right? what components i should use? thanks

PC fans are designed to be driven by PWM at a much higher frequency than the Arduino's default hardware PWM. That is probably the cause of the noise.

You can change the PWM frequency - http://arduino.cc/playground/Main/TimerPWMCheatsheet http://arduino.cc/playground/Code/PwmFrequency

dxw00d: PC fans are designed to be driven by PWM at a much higher frequency than the Arduino's default hardware PWM. That is probably the cause of the noise.

You can change the PWM frequency - http://arduino.cc/playground/Main/TimerPWMCheatsheet http://arduino.cc/playground/Code/PwmFrequency

Yeah, the default's right smack dab in the voice/ear sweet spot of the audible range at 976 Hz. Probably for newb's like me to hear it when we hook up a speaker to it in our "PWM, hello world sketch"! XD

Thanks for the references.

Here is something fun you can do with PWM - a nightclub that fits in your pocket -

http://www.youtube.com/watch?v=fTmLKKLv5cE

All the sound is being generate by one Arduino Uno using 8 bit PWM from pin 6.

I am writting up the project at the moment and hope to publish the source code and schematics in a day or two - its very simple to built - 2 pots, 4 leds and resistors and your pretty much finished.

Duane B

rcarduino.blogspot.com