how to use a potentiometer

[Dolla]

Hi,
I was wondering if somebody could tell me how to use a potentiometer? How would I place a POT in my PSU so I can control the fan - as seen in this article -
http://www.silentpcreview.com/modul...ons&file=index&req=viewarticle&artid=9&page=5

I would like to do what he has done. Are there any risks I should consider? How would I connect the wiring onto the POT (there are three connectors, 2 wires...).

Thanks in advance.

-$-

 

[ScottMac]

Well, first off, you shouldn't be screwing around power supplies if you don't know what you're doing. IT's dangerous, you could hurt yourself or others, and potentially start a fire.

That being said, the answer to the question is that there are three legs on the potentiometer ("pot" for short), the two on the outside are the two ends of the total resistance path (if you have a 10K pot, the two ends are and always should be 10K ohms). The middle leg is attached to the movable arm connected to the stem that you twist when you want the resistance value to change (like a volume control).

When you only use two of the three arms, you're really just using the pot as a Rheostat (variable resistor), FWIW.....

Anyway, one side should connect to one of the outside legs (usually the right side, so that "loud / up" is a clockwise rotation), and the other lead goes to the middle leg.

Be very careful to choose the right voltage, current, and wattage rating for your pot...if you do it wrong, lots of things are likely to go up in smoke.


Good Luck

Scott

 

[ClaudiusD]

There is a more conventional way to use the pot for your application. A pot is made to be used as a voltage divider. Using it, you can basically tune down the voltage from whatever the original voltage is to 0V. This is how you would use it with a fan:
The fan should have 2 wires going to it. Lets say that one is red and one is white (just for reference, if your wires are different colors it won't make a difference). Snip both wires. Connect the red wire that goes to the fan to the center leg. Connect the other piece of red wire to an outside leg. Now connect both white wires to the other outside leg.
This will act as a voltage divider. When the pot is turned to one side, the fan will get maximum voltage and when it is all the way to the other side the fan will get 0V. You can now tune down the speed of the fan until the noise level is satisfactory.

 

[HouRman]

I did it on my case, it's very simple to do and I mounted the knob externally.

Choose a rheostat that's at least 4 watts and you'll be OK for PC fans. The resistance will vary due to the amperage your fan uses. For example, a 25 ohm rheostat works perfectly with my 120mm fan. The fan never stalls and can be adjusted from quiet, to roaring.

Do a google search for rheostat and you'll find the math.

I just soldered the black wire of the fan to the rheostat and mounted the rotary knob on my case, simple $4, yet effective to adjust the fans rpm.

Link

 

[Dolla]

HouRman,
I went ot your computer page and I noticed that you use a lot of Dynamat... Can I haveyour opinion on this? Does it actually work?
I'm in the process of making my computer silent (will probably place adjustable Enermax or Panaflo fan(s) into my PSU and also replace the intake fans with panaflos, also am getting Barracuda IVs... all of these are in the mail).
Once I set all tha up, hopefully things should get decently quiet. However, there may still be some noise... therefore I need opinions on how effective the Dynamat and Pax mate stuff is...

Thanks in advance.

-$-