It's been awhile since I have been here. I took a long hiatus to work my business, and my real job. But now I have time for my hobby, so I have a question…

I have a few PIC microcontrollers that are USB capable, and I want to use one of them to control the fan speed (individually) of the numerous fans in my PC, using software I create. Some fans will have speed reporting, some will not.

I was hoping that someone here has done this, and can help me pick the right semiconductor device to control the fans, the right mosfet, or whatever, and the way the speed is controlled. Either by voltage level, or something pulse-width modulated.

I just received my 5lb Mouser catalog and that pushed me to get back into developing with the PIC. I want to do something that I can send a command to my device and increase/decrease the speed of an addressed fan.

All I want is references to schematics, device reference numbers, et cetera, so I can make this happen.

Thanks!

Gary.Hop

EDIT: For sake of clarification, the fans are 12vdc, don't know the amperage, but I'm sure it can't be that high. They are either similar, or exactly like Panaflo fans. 80mm.

For a start I would suggest you test the fans to see if you can use PWM to control their speed! - most fans use DC brushless motors, and the internal electronics might not work fed from PWM.

Hmm, to test them, I would still need a mosfet or something like it wouldn't I? I doubt if my fingers could move fast enough on a SPST switch to simulate PWM (sorry, a little humor).

Thanks Nigel for the suggestion though. I was going to use PWM, and I didn't know about the problem with brushless motors. I just need some suggestions for a mosfet(s) that would be good for the job. There are so many to choose from.

Thanks again!

Gary

You could use a MOSFET, or a conventional transistor, and use a 555 to generate the PWM signal - there are various designs like that on the net, for speed control.

Those are good links. Thank you. I did a google search with the subject line of this thread and found a bunch of others too. I guess I should have googled first, but I like the advice I have gotten here, so I gave it a shot.

Sucks about the speed reporting made inaffective by using PWM. I'll see if that happens to me. I guess I could shoot an infrared beam through the blades to get the speed if I need to so that's no biggy.

Thanks for the help!