PC Fan Controller

Hey guys,
Hoping someone might be able to help me here with some simple-ish electronic stuff, that i haven't learnt yet.
Looking at making a Fan Controller for my PC.
Making, why? Because i want a custom one that i am able to turn on/off fans, control the speed and a small LED to say if they are on/off..

I've done a fair bit of research but i can't really work out exactly what i need without asking someone..


If i run 12v power, into a switch, then through to an potentiometer, how do i determine the size of the potentiometer?

I am running these fans: Click here
which run from 12v, current is 0.14A(+-10%)
I think this working out is correct:
Vf = Fan Voltage desired
Vs = Power from the PSU (12V for the yellow wire, 5V for the red)
Rf = Fan Resistance (in Ohms)
Rr = Potentiometer Resistance needed (in Ohms)
Vf = Fan Voltage (12V, 7V, or 5V)
Va = Fan Amps (usually between .1 and .5)

Formula:
Rf = Vf/Va
Vf = Vs(Rf/(Rr+Rf))

5 = 12(120/(Rr+120))
.418 = 120/(Rr+120)
.418(Rr+120) = 120
Rr+120 = 288
Rr = 168 Ohms
So the potentiometer should be 200ohms?

What i really want to know is, will the attached diagram work - with the correct components?
what size resistor will i need after the potentiometer to run the LED's? Or is that tricky because the potentiometer is varying the current?

Appreciate any help in advanced..

I would lean towards using a circuit more like the attached. The major fault with even the attached is that the LED simply tells you there is power to the fan but noy if the fan is moving any air spinning. The series LED resistors in the attached are based on a LED with 1.2 V forward voltage drop and about 15 mA forward current. The series resistor for the LED will have a value that is a function of the LED current and voltage.

Vsource - V LED / LED Current

About the same for the fans but I used about 150 mA max. I figure about 50 Ohm pots should work.

There are PWM circuits out there for fan speed control also but if you just want a few pots and switches with LEDs the attaches should work.

Ron

Thanks for the reply Reloadron!
That circuit looks perfect, thank you very much for drawing that up, and with the details. What software did you use?
You actually did everything i wanted.. you're a champ, thanks!

No problem, my pleasure. I used a version of Orcad Capture but only because I had just gotten to work and was having coffee when I drew it. Most people here use a few pretty good schematic tools that are free. Eagle has a light free version as well as others. If you start another thread just ask, the guys will give you some great suggestions as well as help using it.

Ron

How about that?

It fits into a 5 1/4" bay of the PC (size of CD-DVD readers/writers) and controls 4 fans independently. It also features optical and audible alarm at over temperature.

It is delivered with four temperature sensors and four 3-wire cables for fans with tachometer output to indicate fan rpm.

Check out reichelt elektronik - OnlineShop für Elektronik, Notebook, PC-Komponenten, Flachbildschirm, Festplatte, Karten, Kabel, LED for FANMASTER SF509.

Boncuk

Reloadron said:

No problem, my pleasure. I used a version of Orcad Capture but only because I had just gotten to work and was having coffee when I drew it. Most people here use a few pretty good schematic tools that are free. Eagle has a light free version as well as others. If you start another thread just ask, the guys will give you some great suggestions as well as help using it.

Ron

Click to expand...

Cheers for the quick touch down. Got Eagle and running through some small tutorials, legend!

Boncuk said:

How about that?

It fits into a 5 1/4" bay of the PC (size of CD-DVD readers/writers) and controls 4 fans independently. It also features optical and audible alarm at over temperature.

It is delivered with four temperature sensors and four 3-wire cables for fans with tachometer output to indicate fan rpm.

Check out reichelt elektronik - OnlineShop für Elektronik, Notebook, PC-Komponenten, Flachbildschirm, Festplatte, Karten, Kabel, LED for FANMASTER SF509.

Boncuk

Click to expand...

Hey, cheers for the suggestions, never seen that before. Great suggestions, will look into it more