What sliding potentiometer would I need to control 0-12v? and how do I wire one?

I would like to control 12v DC with a sliding potentiometer. I would like the current to go from 0-12v DC, but I dont know whay resistance to get? 
I would also like to know how to wire them as I noticed the had 3 terminals, mabye ones a ground?

If you have a really good awnser you may get a patch.....yes, I am giving away loads right now

thanks

Oscar

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NachoMahma7 years ago
.  As its name implies, a potentiometer is designed to control voltage (see also voltage divider), not current. Rheostats are used to control voltage at high current. Potentiometers have three terminals; rheostats often have only two.
.  Using a resistor to control voltage at high current levels is inefficient and may produce enough heat to be a fire hazard. Check into a variable voltage regulator. Since I see "lights" in your keywords, you may want to investigate PWM.
oscarthompson (author)  NachoMahma7 years ago
sorry I made a error... I was typing it up fast before I went to work...
I was looking at your awnser and I can undersatnd what you are saying but your links appear to be broken?
.  Wikipedia is offline for some reason. The links should start working as soon as Wikipedia is back up and running.
SafnilS2 years ago

hey is there anybody to help..... i need a potentiometer or rheostat to vary dc 0-12v... can u help me to the rating or ohm

mathews7 years ago
There are normally 3 terminals, two end terminals which would be connected to + and 0v, and the center wiper terminal.

What are you going to use the voltage for? The pot will either not be able to supply enough current, or a lot of power will be wasted on it. It might be better to use a large pot (~>10k) to control a supply instead.
oscarthompson (author)  mathews7 years ago
I am using the voltage for controling lights.. I don't mind how much power is lost. Its pluged in to the mains
They'll waste as much as the lights consume. You're much better using a mains  dimmer on the transformer input..
oscarthompson (author)  steveastrouk7 years ago
That would work but I have 4 channels which need a sliding pontentionmeter each.. which is running of the mains 
So you need a dimmer per channel, B+Q will do something suitable for a few quid. A largish rheostat will cost a lot more than a dimmer !

Screwfix do single dimmers for a fiver a piece....
oscarthompson (author)  steveastrouk7 years ago
I'm sorry but im not looking for somthing like that.. Do you know what potentionmeter i would need if I used 12V LEDS for a spotlight..
So now they're not 50W ?
oscarthompson (author)  steveastrouk7 years ago
The 12v LED spotlight is a complete different product....there about 5-10w
Its just you had said they were 50W when you were asked....

5-10W is still an expensive pot - no change from 20 quid there. Each. 

Do it with this circuit, and it's cheaper and better for the LED too
trimmable current source.JPG
oscarthompson (author)  steveastrouk7 years ago
Ok.....I want to make this simple, its not a very big project......Rule out all of the spotlight idears (the ones I mentioned above). If I made my own spot light with about 20 LEDS to each light, would a product like this be sutiable

Or I could rule out the linear pot idear because this is what I have made already (the picture), and I could spend my money doing other things to improve it

Thanks for all your help

Oscar
101_5077.JPG
No, that pot has too much resistance, and it can't handle the power. My circuit costs about 2 quid per channel.
oscarthompson (author)  steveastrouk7 years ago
How is the voltage adjusted though?
It isn't directly, this thing controls the CURRENT very accurately, which gives you  the same effect.
oscarthompson (author)  steveastrouk7 years ago
I'm not getting this? Is there any physical controling of it? what affect do they give?
Physically controlling what ? The current ? Yes, the circuit keeps it at the constant level set by the pot in the circuit. It does THAT by controlling the voltage across the 0R5 and keeping it constant.

Steve

oscarthompson (author)  steveastrouk7 years ago
how do you dim the lights?
Turn/slide the pot !
oscarthompson (author)  steveastrouk7 years ago
ok! now I get it now... thanks
.  If you are trying to run 10W of lights, you will need a pot rated for at least 10W. If you are running 50W of lights, you will need a 50W pot. ...
.  You are not likely to find a slide pot rated for over one-half Watt (0.1W seems to be pretty "standard") and if you do it will be very expensive and generate a lot of heat when the lights are dimmed.
.
.  If you are running LEDs, you can find formulae/forms to calculate the value of current limiting resistors. Use this figure as the minimum value for your pot. Make sure your pot can candle the power.
While you can easily connect a potentiometer to act as a voltage divider, I do not suggest it.  Potentiometers can usually only handle about 1/4 watt, and I suspect your lights will draw more than that.  If you just use a pot, it'll evaporate in a puff of magic smoke within seconds.

What wattage are the spot lights?
oscarthompson (author)  jeff-o7 years ago
50w
Ha, yup, *POOF*

You'll need a purpose-made dimmer for those lights.  Take a trip to a hardware store, they'll likely have what you need in the electrical or lighting section.
Re-design7 years ago
You need to start with something like this.  You can sub a potentiometer for one of the fixed resistors and you'll have a basic variable power supply with no frills.

Since I don't know what you're really doing with this I can't guarantee that it will work for your real purpose but this does answer your question.
oscarthompson (author)  Re-design7 years ago
the purpose is to control spotlights
"volts" are not "current" what are you aiming to do ? Control the current in a hot wire or something ? 

If you really mean "adjust the voltage across my load from 0..12V" then we need to know the resistance of the load.

Steve
oscarthompson (author)  steveastrouk7 years ago
sorry I made a error... I was typing it up fast before I went to work...
I am aiming to control spotlights.
A copper rod, a copper plate, and a barrel of seawater is all you need.