12v to 3v and back to 12v using a potentiometer

[Ray450R]

Hey ladies and gentlemen, i need a little help. I want to go from 12v to 3v and back to 12v using a potentiometer. Just not sure what ohm potentiometer i need. Can someone tell me what ohm i need. All the help is appreciated. Thanks

 

[Gryd3]

Hey ladies and gentlemen, i need a little help. I want to go from 12v to 3v and back to 12v using a potentiometer. Just not sure what ohm potentiometer i need. Can someone tell me what ohm i need. All the help is appreciated. Thanks

Depends on the application.
If you are using it for a small signal or reference voltage, you can use a wide range of pots.
If you plan to operate a circuit on the voltage. (ie, an adjustable power supply) Then your proposed solution will not work.

Please elaborate and we can figure it out,

 

[Ray450R]

I have a 12v switching power supply and im trying to build this. Doctor Who 2 Line E hooka Lunch Box Mod, 1.5-3.5 …:

 

[Gryd3]

I have a 12v switching power supply and im trying to build this. Doctor Who 2 Line E hooka Lunch Box Mod, 1.5-3.5 …:

You are much better off finding an adjustable DC-DC converter.
Because you are dealing with a higher load requirement. (Heating element) the potentiometer will not cut it... Any power being 'held-back' will just heat up the potentiometer instead of the heating element.. and those things are not meant to get hot

If you find an adjustable power-supply, you can reposition or replace the potentiometer on the board to complete your mod.

 

[Ray450R]

Awesome response!!! If i do that what would i use for a potentiometer? (What ohm). Sorry if i sound stupid im new to this electronic building.

 

[Gryd3]

Awesome response!!! If i do that what would i use for a potentiometer? (What ohm). Sorry if i sound stupid im new to this electronic building.

I can't give you that answer right now...
You can approach this one of two ways... buy a pre-made adjustable power supply or DC-DC converter. Or build one from scratch.
Regardless the potentiometer will depend entire on the circuit it's in or designed for. It very well could be 1k Ohm, or 10k Ohm. There is no way to be certain until the product is designed, or looked at.

I tried to post another Electronic Point thread that could help... but honestly, even searching for 'adjustable' brings up lots of threads that apply to what you are attempting.
You know the voltage you want to work with, the only missing info is how many amps you want to be able to supply. If you have a 10W heating element, you can assume that you will need an Adjustable DC-DC converter or power supply that can provide 3V - 12V and 1+Amps.
This is going to be a dual output, so you would need two adjustable DC-DC converters or power supplies if you want to individually control the temperature of each output... Your call on this though...
Alternatively, because you are using a heating element, you can quite easily use PWM. If you are unfamiliar, PWM will rapidly turn the device on/off so it 'averages' out to be a lower output. You can easily adapt this to your application as well. (And I know there is a motor speed thread here somewhere that has someone doing this with PWM. I know you are not using a motor, but the circuit will be the same )