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Fan Controller for big fans

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OP
gbaz

gbaz

Member
Joined
Feb 23, 2003
Location
New Orleans LA.
the controller can use 5-15v, and can controll a motor up to 100v, 7.5A. No multi controller ive seen comes near that. Dont like the way it looks? dont mount the pot on the pcb, use wires to remote mount it.
 

L337 M33P

Member
Joined
Jun 5, 2003
Location
TEH INTERNETS
I was about to write a damn ARTICLE on this for the front page! ARGH

But my design has two channels, runs off 12v and has a power-on delay to run the fans at 12v for a couple of seconds. Meh, I suppose it's different enough to warrant an article :)

That fan controller is Pulse-Width Modulation. It *may* work with the sort of fans found in computers but they are DC brushless fans - electronics inside controls the stationary coils that attract or repel magnets on a ring on the outside of the fan. Switching them on and off at high speed is not going to make them happy, and the fan may not work.

In a short while (and Ed willing) I will have an article on the front page detailing how to build your own two-channel high power fan controller. It can do 3A on each channel, is ~85% efficient and has smoothing circuitry which means that a) fans with RPM sensors will still give readable signals and b) it will work with brushless motors. The price of components will be about $20 if you already got some stuff lying around.
 
OP
gbaz

gbaz

Member
Joined
Feb 23, 2003
Location
New Orleans LA.
I was wating for your artical and got bored. Ill give it a this thing a shot, if the fan freaks out ill wate for your artical :) If ed wont post your artical ide still like to read it.
 

mccoyn

Senior Member
Joined
Nov 17, 2003
Location
Michigan, USA
Don't most motherboard connectors use PWM?

Its strange, when I set my multimeter to DCV, it gives anything below 12V depending on what speed I have the fan running at. When I set it for ACV it gives 24V no matter what I set the speed at. I always assumed this is how my multimeter reads PWM.

Hmm, I'll have a homemade oscillascope soon I could check it with. I won't have time to work on it until after new years.
 

L337 M33P

Member
Joined
Jun 5, 2003
Location
TEH INTERNETS
If they were using PWM then they would be able to handle much more current than the 350mA or so that is the typical maximum. I think they use standard linear MOSFET operation or something with a controller chip.
 

mccoyn

Senior Member
Joined
Nov 17, 2003
Location
Michigan, USA
PWM still needs a MOSFET to turn the power on and off. There is no way they run the entire current for the fan through all the logic that generates the PWM signal.
 

L337 M33P

Member
Joined
Jun 5, 2003
Location
TEH INTERNETS
Some images of my fan headers: (56k beware, 800kb each)

http://www.uploadit.org/L337M33P/Fanheaders.jpg
http://www.uploadit.org/L337M33P/FanheaderCPU.jpg


What I meant to say was:

Because there is a 350mA limit on fan headers and no obvious large MOSFET around with no heatsink on, I will assume that the output is linearly controlled via a Digital-analogue converter with an output transistor driven by the Q-fan chip or whatever, that is tied into the hardware monitoring chip. A basic PWM design would mean that not all fans will work with the pulses, so a form of smoothing needs to be implemented. There is only one small cap near each of the fan headers which is not enough to smooth out the voltage enough. There is probably a small MOSFET knocking around somewhere near the fan headers, but I can't see it in the photos. Unless you get an oscilloscope on a fan header that is under a reduced speed you cannot be certain.
 

mccoyn

Senior Member
Joined
Nov 17, 2003
Location
Michigan, USA
Alright, I'll do just that. I couldn't find the parts to make my oscilloscope work so I had to order them. I should be able to verify it (for my board at least) in a couple weeks.
 
OP
gbaz

gbaz

Member
Joined
Feb 23, 2003
Location
New Orleans LA.
cant get to your pictures l337 :( And i bet most mobos use same way to controll fans, if yours does use PWM chances are most of them do.