Hey Guys,
I want to make a PWM fan controller from my PC because the stock one is just horrible.. But i need help designing a circuit and finding parts..
It needs to follow this standard 4-Wire fans
I plan on being able to change the fan speed through usb..
If any one could give me a hand, that would be greatly appreciated..
you can use an arduino, see Controlling 4-pin computer fans - PWM at 25khz? - Interfacing - Arduino Forum.
Sometimes you can get away with a lower pwm frequency, but this may shorten the life of the fan(controller), it also makes things a little noisy (fan may start to whine, or suddenly go flat out to max rpm at a low duty cycle).
It is recommended to put an optocoupler on the tacho line, and add some serious decoupling to remedy the electrical noise from the fan.
Also, make sure that when there is no control input, the device keeps the rpm a a safe minimum level (make it "fail-safe"), otherwise your CPU is going to be in thermal protection mode before your OS (and thus the control software) has finished loading.
Pieter
ok I will have a look at that.. and there is not need for a fail safe.. the Intel standard requires fans to max rpm when there in no signal