Potentiometer question

[rudiemcska]

I'm pretty new to this stuff and have no formal training so forgive me if I'm asking a stupid question.

I'm trying to use multiple Potentiometers from an old TV to vary voltage to a RGB LED strip light. When I put 12v to the potentiometer I'm only getting a maximum of 8V out of it when it's fully "open". I don't have a model number on the potentiometers but when I checked their "open" resistance I get 4.8kΩ as a resistance. From what I understand this shouldn't explain a drop of 4V's through the potentiometer. Can someone clue me in?

Thanks for your help in advance.

[kaboom]

Re: Potentiometer question

Don't pass the load current directly through the pot. The end resistance is too high, leading to voltage drop, and the current will burn up the pot.

Instead, use the pot to control either a pass transistor, or, for less heat, a PWM control with a MOSFET.

For small loads, a heatsinked pass transistor will work.

[rudiemcska]

Re: Potentiometer question

Given I'm getting the voltage drop do you think the damage is already done? I'm not sure what is considered a small load honestly. I can tell you that the full strip of lights pulls 36W but I doubt I'll be using the whole strip.

[kaboom]

Re: Potentiometer question

Did the you get smoke from the pot?

These strips, do they have any electronics on them? Or are they just LEDs and resistors?