12V PC fan controller

[cooee2]

This is my first post and I'm new to electronics.
I want to build a circuit to reduce excess speed/ noise on a (12v 0.08A) fan in my PC. It's a two wire setup I rigged to actively pull air into the PC case.
Then, with a separate circuit, I'd also like to be able to control the speed of my (12v 0.28A) CPU cooler. It's also way too fast and noisy for its heat sink which is virtually always cold. This CPU fan however uses three wires and gets its feed from the mobo CPU fan hook up.
I tested a 1k carbon potentiometer on the 0.08A (two-wire) fan, it worked fine, but started to get a little warm. I want it to be reliable and I'd like to take heat away from the carbon pot - the Tandy guy suggested a transitor. Any thoughts and (easy to understand) diagrams please.
Regards, cooee2

 

[justDIY]

if your 80mA fan is making audible noise, it's time to replace it ... are you sure it's not 0.8a?

as for the cpu fan, search out a program called speedfan - it will control your cpu fan via software. your motherboard BIOS should also have an option to control the cpu fan. any sort of external speed controlling device you cook up will prevent your system from monitoring the cpu fan, which in general is a bad idea.

"Tandy's" suggestion of a transistor is good, it is easy to heatsink a transistor and have it burn off current to slow the fan down.

Most people seek fan controllers for systems which have 10s of watts of fans (mine has three 18 watt fans (1.5a) and several smaller ones). I use an external pwm circuit to control the big ones, the small ones are controlled by my motherboard via speedfan.

this site has some good info for you regarding fan noise control:
http://www.cpemma.co.uk/index.html

this site has a nice and simple linear temp control circuit:
http://www.heatsink-guide.com/control.shtml

good luck!

 

[Sceadwian]

If your PC has a feedback wire on it's fan it should have bios option to automatically adjust the fan speed. Mine does and it's a pretty old motherboard (Asus A78NX) The rest of the fans are probably not needed as long as you get the airflow in the case right. I only use the power supply fan to exaust heat from my machine and it's always cool, even with both the video card and CPU/mem are overclocked.

 

[cooee2]

Hi JustDIY and Sceadwian,
The mechanics (bearing surfaces) of the fan are fine and the blades are clean. It's a fluid dynamics issue. The speed is excessive, hence the wind-noise. Thermally, at current RPMs, things are overcatered for.. the fans don't need to rev so high. A 40 to 50% reduction in RPM would still be adequate for cooling.
I want to be able to proportionally vary the voltage - reliably and efficiently. I'm generally good with a soldering iron and would like to 'perfect' this project.

Re: "any sort of external speed controlling device you cook up will prevent your system from monitoring the cpu fan, which in general is a bad idea" I take your point. Hmmm - so where to from now?

It is definitely (zero-point-zero-eight ampere) 0.08A. Rather efficient for a 'standard' 80mm fan, but it's not really the noisy one. The noisy one is the CPU fan which is 12V 0.28A - with 3.5 times the power consumption.

I did check out the BIOS (beforehand) and I have no means to regulate the speed via this method. I can only Enable/ Disable but little else. The BIOS option is annoyingly very limited despite it being a 4yo Gigabyte GA-8IPE1000 Pro2 mobo. And yes 'fan feed back control' should mean "control" but it doesn't (much) in this case. "Full bore" is all it seems to understand. I'll report back re those sites you recommended JustDIY.

I live in hope that my next PC mobo will have several BIOS fan speed control options.

Re PC case air temperature concerns: I designed a PC air filter for the fan driven incoming air. Internally, I now rarely have to clean my fan blades, heat sinks, PSU, etc. I come from an audio background and I want (am aiming for) an absolutely quiet PC. If my radio or hifi had hum, it'd be a fault, and so I'd have it fixed or relegated to a noisy environment. Seems PC engineers and their companies are mostly too busy 'gaming' aka, playing with themselves to worry about a more discerning market. 'Just quietly', this could be 'game on'. Thanks guys. Regards, Cooee2.