Speed-dependent rheostat cooling

[Crazy Jayhawk]

If you're using a rheostat to control fan speed like I am, you know that it becomes quite warm when turned down. Some of you may never experience this problem, but this is an overcomplicated solution, my trademark. :)

Basically, this involves affixing an HSF to the back of the rheostat. A resistor is added to the HSF live wire because the fan by itself will probably be almost unaffected by the resistance change in the rheostat. I'm not sure how many ohms you'd need.

How does it work? Simple. When you turn the dial, the two outer terminals change in opposite directions. Turn the fanbus voltage all the way up and you won't need much cooling for the rheostat. The HSF will almost stop with the proper resistor installed.

Turn the rheostat way down and you'll need to dissipate all that heat. When the fanbus is turned way down, the HSF is turned up, and vice versa.

This might work and it might not. And to prevent the rheostat terminals from contacting the case, there's a simple solution. Get heat shrink tubing large enough to fit over the terminals and you can effectively insulate them from the case metal.

[dimmreaper]

Why not just make a variable switching supply to run your fans off? I'm going to get around to doing that some day.

[Crazy Jayhawk]

Originally posted by dimmreaper
Why not just make a variable switching supply to run your fans off? I'm going to get around to doing that some day. Because that would be too simple.

Overcomplicated is my middle name. :D

[Patchmaster]

Other than because it's overcomplicated, is there some actual reason you want to put a fan on the rheostat? As long as you haven't exceeded its rated capacity, the rheostat should be fine. I have to admit, though, it's a clever and completely logical use of the other lead on the rheostat.

[Crazy Jayhawk]

Originally posted by Patchmaster
Other than because it's overcomplicated, is there some actual reason you want to put a fan on the rheostat? As long as you haven't exceeded its rated capacity, the rheostat should be fine. I have to admit, though, it's a clever and completely logical use of the other lead on the rheostat. Maybe if you're paranoid about it overheating...

And thanks for the compliment. :)

[SteenkyBastage]

my solution was to hang the rheostats in the fan's intake or exhaust, depending on whichever is inside the case. the fan will in effect cool its own rheostat.

however, this may not satisfy that "overcomplication" thingey...

[dimmreaper]

I just thought of something, and with the right size rheostat, I think it would work.

Wire the fan(or fanbus) possotive wire to the center terminal on the rheostat. Wire the PSUs +5V wire up, with a diod, to one of the side terminals. And wire the PSUs +12V wire up to the other side terminal.

This way you wouldn't be just relying on the rheostats resistence, but also a voltage change as you turn the knob from one side to the other.

I think this would work, but I think you should double check this with Hoot or Colin, as they are the CircuitHeads around here :)