Potentionometers

I need a refresher electronics course - How do you hook up a pot ?  I want to be able to vary the speed of a DC fan (for light show purposes) and cannot for the life of me recall how to wire the pot !  Can anyone assist ?
It has three leads off of it - looking at the front of the pot - with the shaft pointing up - I have one on the left, one in the middle, and one on the right (prongs) pointing right at me.

Usually the middle prong is the "wiper" or moving contact, and the other two are the ends of the resistor strip.

Watch the power rating of the pot, it has to be enough to control the power you will be running through it - most of them won't handle a lot.

I would be running 12v DC through it - the pots LOOK beefy enough - they are 1K OHM. So - I know the 12v positive lead is going to go to the pot - but HOW exactly ? I have drawn a complete blank With the three leads to choose from - I am about to just strip some wires and test !

Do you know how much current you'll be pulling? ( V x A = W )

Connecting power to one of the outside leads, and the center lead to the motor, should do it. Which outside lead you use will decide which direction you will have to turn the knob to turn up the juice.

Are they wire wound pots (do they make a slight zzzzzz sound as you turn the shaft)?

Ragnarok said:

Do you know how much current you'll be pulling?  ( V x A = W )

Connecting power to one of the outside leads, and the center lead to the motor, should do it. Which outside lead you use will decide which direction you will have to turn the knob to turn up the juice.

Are they wire wound pots (do they make a slight zzzzzz sound as you turn the shaft)?

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Well, it's a12volt, 400ma dc power "wall wart" type. so - around .5 Watts (right ?)

no - they are the carbon ones - should I get the wire wound ones instead for this ?

Well, 12 volts times 0.4 amps gives 4.8 watts. Most carbon type pots are designed more for signals than for power, so you might roast it on 12 volts depending on how much current the motor actually pulls.

Me, I'd hook it up and try it out. If it gets slightly warm at full blast after running for a while it'll probably be ok. If it gets hot in a few seconds to a minute, I'd find something more robust, like an actual controller such as the example here:

http://www.bakatronics.com/shop/item.asp?itemid=383

i think "wire wound" means a reostat. i may b wrong but try pos from source to one side term, neg to center, thenuse the other side to your motors pos,and get your neg to motor from that same center term. in other words power in is an outside connection(+) and the center connection(-) and power out is the OTHER outside connection(+) plus the center(-) connection. center is common. but PLEASE, before u do anything i suggest, check w/ a multimeter. even though i have fixed/repaird stuff that surprised hell out of me, i have destroyed far more...i call it "learnin thangs" but now i think on it u may be better off w/ a reostat as i don't think a pot will handle the load of a motor.

I'm glad you guys have brought this up as i've been thinking along these line but i'm not that knowledgable, so break it down idiot proof for me please as i'd love to build a quality X-Y scanner..

Timelord said:

I'm glad you guys have brought this up as i've been thinking along these line but i'm not that knowledgable, so break it down idiot proof for me please as i'd love to build a quality X-Y scanner..

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Well - after I burn some stuff up trying to figure it out - I will post my results ! They are el-cheapo PC fans - so if they smoke, no biggie, I think I have a million of them !

Yeah, an electronics person would have more fun doing it themselves, but I like the solid construction of something that's actually meant for the purpose. For ~$20, you can get a 4 fan controller from SVC compucycle or somewhere else that is meant to go in a regular computer case and run off a standard 4 pin molex connector from a computer PSU. You just plug in regular CPU fans (I bought a few cheapo 80mm $1.50 fans) and there are 4 knobs in the front you can adjust the speeds with. I also picked up a some decent $20 computer PSUs from Newegg which I like because I can use them with the controller, fans, or hijack the 12V lines for TECs or other things. Maybe not quite as cheap as doing it from the bottom up, but its still not a very expensive setup and it works quite well for me. Good luck!

Post pics boys

u guys all got me goin w/ this so heres what i did: first i blew up all different kinds of outta whack mirror thingies because of centrifical force. THEN i made a mirror out of a quarter..ground 1 side down then polishpolishpolish. drilled tiny hole dead center then tried to mount it perfect on o small mandrel.thats the secret...u can't get it perf,but i swear if u try to get it outta whack it will only roll perf straight clean. anyhow i put it on a DREMEL,cut light and aimd ARIES 100mw..whoa! timetunnel! smoke REALLY intensifies the effect...if ya know what i mean!