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Has anyone attempted a homebrew fan controller?

yeah he got the necessary link.

best are 50 ohm for case fans, 20 ohm for cpu, but I have looked, and can find neither that will support the required wattage, so you will have to go with an electrobus probably. I have most of the parts for my electrobus, but I still need the IC.
 
Make sure it's not like the "Drill speed Controller" I bought in kit form, assured by the shop dude it was what I was after... Works well, but it operates by sending pulses, hence, a nice whirring noise, changing pitch depending on speed... that was IC controlled too....
 
Around 50 Ohms at 2 Watts or more are good for fans up to 0.4 Amp or so - I got some 100 Ohm 2W pots from bgmicro.com that work fine for up to .4A fans but I don't get to use much of their rotation on some of my fans. Allelectronics.com had some 15 Ohm 15W rheostats that should be good for just about anything, but might not be able to slow down the low power fans as much as they could be. Over 0.4 A or so you might want lower Ohms with a higher power dissipation than the 100 Ohm pot.
. Fans also work best if they start at full speed and then throttle back if desired. You could rig up a timed relay that would bypass your rheostat for startup and when the timer kicks off (only a second or two), trips your rheostat into the circuit. This idea is good for both passive and active controllers.
. Many (if not most) of the commercial controllers actually use variable voltage regulators. At that point, lighter duty pots can be used as they won't be directly in the high power circuit. This works best because you don't have to worry about matching the pot to the fan. That low-loss automotive linear regulator mentioned in one of the bit-tech links looks like a great idea - wonder how $$$s they cost?...
.bh.

It's Sunday, have some :wine: !
 
What's the formula for figuring it all out?
0.4A is a good bit of current, even for a 120mm fan.
 
My little 70mm CPU fan pulls 0.4A at full cry - and cry's the word!
I(Amps)=E(Volts) / R(Ohms) restated as R=E / I so my fan is 12V / 0.4A = 30 Ohms - calcs the approx. (~) resistance of the fan. The commonly used DC fans generally operate from 60% of E to full so the pot should generally equal the fan in resistance - though one of my 120s only works from ~10V up...
. Then you calculate the power rating for the pot by determining at what point the most power is being dissipated by the pot. Power (W)=IxA for non-reactive DC circuits. Current (I) will range from the rating of the fan with the pot at 0 Ohms to about 60% the rating of the fan at the slowest speed. And voltage (E) drop across the pot will range from ~0 to 5 (assuming 7V is the stall point of the fan).
. See how it's far easier to just do an active circuit? Easiest for a passive circuit just to get the R close to that of the fan and get as big a Watt rating as it ever might see.

.bh.
 
It's the other part I couldn't remember.
I'm personally going with a variable voltage regulator, as I searched high and low, and could not find a rheostat around 150ohm. With a pot and variable regulator, I can use any pot out there, and then just get the right resistor for it, which is reasonably cheap and easy.

...too bad the Sunbeam controller is so ugly. Otherwise, I'd just use it.

Oh, and I can imagine .4A is loud. my Panaflo L is loudest single thing in my box, and it's way, way too much at < .1A.
 
Umm, how much are you looking to save? So aesthetics and ease of finding parts and assembly (none), why -don't- you buy one.
 
I just bough the sunbeam off of svc. I didn't get exactly what was in their picture, but its very nice and definitely worth $15.
 
I added front and rear fans to the kids case this weekend. The were nothing fancy, and a little loud, so I also added a rheostat from Radio Shack to control them. A 3 watt/25 ohm (or was it 30?) worked great, and was in-stock. Reduced the RPMs from about 2600 down to around 2100 and they are almost as quiet as pre-fan install. The rheostat is almost at its middle position, so I still have a lot of control left if I wanted to go slower. Still good airflow, without the helicopter effect! I just spliced the rheostat into a an extra Molex 4-pin extender cable I had (the yellow 12V wire, which is what these fans used), and then drilled a hole in the back of the case to mount it (3/8" main, 1/8" for keeper). I think the rheostat was $3.99. You could do the entire project for $20 and really help cooling while still being quiet!

I think the folks selling these on ebay must do something similar, but probably buy their rheostats in bulk to keep there prices down.
 
i've built this one and i like it. heres the link

the LEDs dim and brighten according to the turn of the knob which i thought was a nice feature.
 
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