Rheostat/Potentiometer help

[Blebbz]

Ok so I'm going to make a Baybus, using some potentiometers/rheostats, but I'm not sure how much resistance each would need if they had a 12v line going into each of them to take the voltage down to 5v. Any help on which ones I should get?

[dgrmkrp]

That's not how it works. Each fan has a different current draw, so a different resistance to calculate. You could do a purely resistive controller, by using 3 resistors: 1 20 to 50 ohm resistor for the main part, this would have to be rated at a few watts. Then a 1 or 2 ohm resistance for limiting the current through the pot and a pot. This should be like 5k or 10k or whatever. It doesn't mater.

Wire the thing like this:

http://img297.imageshack.us/img297/9962/32128256gv5.jpg (http://imageshack.us)
this is a variable resistor, with a 20 ohm resistance :)

hope you like it, but I do recommend building a controller using a transistor or voltage regulator... Have to go, but hope I helped.

[Blebbz]

Erm... helped a bit, but I'm still clueless :S
Thanks for help

[Kill_Switch]

Try reading this

Link (http://www.valvette.us/dcca02.html)

It may seem like mumbo jumbo if you don't have any electronics training or knowledge. If you got any questions post here and I'll try and answer them for ya.

Also Basic Resistor theory. Skimmed through it, looks pretty good for novices with electronics.
http://www.electronic-circuits-diagrams.com/tutorials/resistors.shtml

[Blebbz]

Hey I can answer my own question! I found a site that's really helpful here, it's got LED barcharts to show how much power is going to the fans. Well circuit diagrams anyway. Here's the link (http://www.cpemma.co.uk/) I hope it helps everybody as much as it has helped me