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PWM Fan Controller

N

NeRd

Limp Gawd
Joined
Dec 11, 2001
Messages
171
Considering that I’ve fitted a noisy delta ’screamer’ in my Core 2 Duo box, I decided to set about making a simple PWM signal generator based on pot position.

I ended up developing a simple circuit to take care of the loud fan, and you can see my thoughts on this in detail here.

Here are some images on my progress:

IMG_1864.jpg


IMG_1873.jpg


IMG_1872.jpg


And here is the PWM signal in all it's glory, applied to the gate of a power MOSFET (IR640), as it's all I have here. You *could* use a power transistor if you wish.

(Min dutycycle)
IMG_1865.jpg


(Max dutycycle)
IMG_1868.jpg


For those who don't know, the duty cycle is the percentage the pulse is high for during a period, i.e. a PWM signal with 50% duty cycle would be a perfect square wave, and if the voltage is Vcc (5v), the avg voltage would of course be half that, 2.5v!

This design is simple, and that's how I wanted it - to control a single fan. That said, it is also scalable to the extent of,
  • controlling multiple fans from a single reference (pot)
  • a reference pot for each fan (tacky imo for over say 4 fans...)
  • buttons to control a menu driven on a LCD, save settings to EEPROM which are loads on the next power cycle..
  • use a graphic LCD :D

..it's very flexible, which is something I like quite a bit!

If you have any questions, just ask :)
 
Oh yea, it's running at a fixed frequency atm, but I plan to throw in a breadboard-mounted pot to select the operational frequency, and check how the fans react based on experimentation. From what I've read the usual range is 30 - 200 Hz...so that would be the swing offered by the freq. pot.
 
deltas dont like PWM... they have bearing rattle..

I wanted to use 2 with my t-balancer (pwm) and they would not get quite.....

they do work with a rheostate
 
Thanks for the heads up, I'll give it a shot and see hrm. Worst case I can throw in a digitally controlled pot and couple it with a VReg (LM317T) and by adjusting it , I can alter the regulated output voltage...

We'll see..
 
yeah i bought my $100 t-balancer so i could have a software controlled MBM5 fan bus for my 2 deltas and 2 panaflos.... but the deltas rattled soooo much... my scythe 60cfm fans are much better but they are quite at 12v so i dont really need the t-balancer :(
 
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