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Is Manual And Auto Fan Speed Control Possible?


ShyGuy91284
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I've got an A7N8X mobo w/ a Barton 2500 o/ced. I've got a SLK-900 and Tornado fan cooling it, and an Enermax Ultimate Controller to control it. I see how I can control the speed of the fan using the dials, and that the alarm will go off if the CPU temp gets too hot. But is there any way to force the fans to regulate the speed to keep the CPU below a certain temp by default, and still crank them up if I want to?

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you can add a thermistor (thermal resistor) to the + wire and mount it somewhere close to the base of your heatsink but this might just slow down the fan - some fans (smart fans) have thermistors mounted to them (little green or blue "match head" looking thing) and have that hooked upto your fan controller but the downside to that is at FULL voltage the fan might only spin so fast if that thermistor is cool and will only spin faster if it gets hot

 

i would advise against mixing the 2 types of fan controllers

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AFAIK thats not possible, it has to be either on or the other, but what minddrive said might work.

What minddrive said is kind of the opposite of what he's looking for; The thermistor would be a lower temp limit and you could choose to run it hotter. Just give me the weekend and I'll try to get the motivation and see if I can create one requiring only a trip to radio shack. If you're really lucky, I'll share it with you guys too. :P

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actually - the hotter a thermistor gets - the more electricity its able to conduct - thats why they put them on fans - they get hot - they spin faster - add that to a variable resistor (fan controller) and you will have an automaticly adjusting fan with the options of turning it up even faster than the thermistor will allow the fan to spin by applying more voltage

 

also - by using a fan with a thermal controller built into it, its lowest speed is say 1100 at its coolest and its fastest is 2200 at its hottest, well with an added fan speed controller you could get from 0 rpm's to prolly 2500 rpms - i use speedfan 4.09 to measure my fan's speeds (it also has fan speed settings)

 

if you mix a "smart" fan with a fan controller - the dial should be set to 1/4 or 1/3 its max setting for "quiet" mode

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If you were to connect the variable resistor in series, the thermistor would act as a cap on the fan speed (thus it couldnt cool the area below a certain point).

 

A thermistor is simply a resistor that varies with temperature. High temps = low resistance. Low Temps = high resistance. Now, if you were to add in a variable resistor between the 12V supply and the fan (in series). The variable resistor would only be able to increase the resistance. A higher resistance means a lower fan speed and higher temps. A fan controller will work the same way, when it is turned "up" all the way, the effective resistance is rather low and when turned "down" the resistance is high.

 

And now that I think about it, you will have a fair bit of fighting between the thermistor and variable resistor. If you were to increase the variable resistor, the temps would rise and the thermistor would decrease its resistance. And if you were to decrease the resistance, the temps would drop and thermistor would increase its resistance.

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Ok, so I've determined the super cheap way to do it and also a nice custom fan controller (which I'll make so you can get all the parts at radioshack just for convinience). I'll try to find the time this week to make a nice pretty guide of the whole thing. Also, I'll include various spin offs such as how to connect it to your mobo's fans. If there are any features that you would like as options, or you think are absolutely needed, speak now or forever hold your peace...or just tell me some other time. I mean, its just a schematic. Not that hard to change.

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