Control of a separate 12v voltage

Hello guys,

So, I have a separate 12v lead whose output I'd like to control with arduino. This 12v is from a pc psu, and it'd control 12v fans by lowering or increasing voltage.

I know arduino doesn't take 12v, but is there a way to control it separately using some kind of a voltage regulator shield? Or a MOSFET?
I can do this with relays and diodes but this gives me very limited amount of control.

I'm not very skilled in electronics so I don't even know how to approach googling this problem as I just get completely different searches.

I'd be thankful for any help!

What do you mean "control it"? The PC PSU is a well-regulated power supply with about 5 or 6 different output voltages. You can't "control" them other than on or off.

The fans are controlled by the motherboard sending a PWM voltage- basically a very fast square wave. Technically it's called pulse-width-modulation, but it controls fan speed and LED brightness quite well.

pwm.jpg

pwm.jpg

By 'controlling it' I mean I'd use the 12v as input and get a variable output out of it.

Not all fans are controlled via PWM, these I own can only be done with voltage as they don't have the 4th, PWM control pin.

As I said, you can't control the voltage from a PC PSU.
If your current requirements are modest, you can build a regulator like this:

regulator.jpg

I would guess that you could control a Mosfet with a PWM signal from the Arduino and filter the output, then feed this to pin 1 on the regulator.

regulator.jpg

3-pin computer fans can be PWM controlled, and is usually done @30Hz.

Can be done low-side (in the ground line), but must be done high-side (in the + line) if you also want to use the tach output.
There must be a zillion web pages about this. Here's one.
Leo..

Alekky:
By 'controlling it' I mean I'd use the 12v as input and get a variable output out of it.

Normally you'd use PWM on the power line, switching the power on and off. That is a different form of PWM control than through a speed control input.

If using a linear regulator you're basically burning off the excess power, very inefficient and for higher power fans you need a big heat sink on that part to get rid of the heat.

[quote[
Not all fans are controlled via PWM, these I own can only be done with voltage as they don't have the 4th, PWM control pin.
[/quote]

That's very true. Do post a link to the specs of your exact fan you have for specific suggestions on how to control it.

Wawa:
3-pin computer fans can be PWM controlled, and is usually done @30Hz.

Can be done low-side (in the ground line), but must be done high-side (in the + line) if you also want to use the tach output.
There must be a zillion web pages about this. Here's one.
Leo..

I tried to control the + line with a MOSFET and this created some sort of buzzing in the fan as the speed is increased.
I've read that this can shorten fans life cycle dramaticaly so I strayed away from the PWM control on these.

wvmarle:
That's very true. Do post a link to the specs of your exact fan you have for specific suggestions on how to control it.

It's just a regular 3-pin pc fan, 12v, around 0.4W, but I'd like to control 4 of them.