New guy- Pot question for 12dc circuit

Discussion in 'General Electronics Chat' started by realbrilliance, Jan 13, 2009.

  1. realbrilliance

    Thread Starter New Member

    Jan 13, 2009
    Hi everyone, This is a great site you have here. I've been looking around trying to find some info on this but haven't been able to.

    I'm looking to make a circuit that would control the voltage from a 12dc battery to a heat coil. From what I'm assuming, a potentiometer would do this function right?

    This seems too easy to work though, as controllers they sell for this function are very expensive. Can anyone help shed some light onto how I could get a circuit to do this? Thanks in advance.
  2. bertus


    Apr 5, 2008

    What kind of coil are you talking about ?
    To heat something with 12 Volts will take some Amperes.

  3. realbrilliance

    Thread Starter New Member

    Jan 13, 2009
    15 watts of heat at 12.8 Volts - is what is stated from the manufacturer.

    The V will prob be more in the area of 13v, as it will be coming from the alternator on a motorcycle.
  4. mik3

    Senior Member

    Feb 4, 2008
    The current is about 1.25 Amps thus you can't use a pot to do that. The pot will glow red:p You can use a power transistor to that by operating in its linear region and controlling the current through the coil with a pot. However, this method is not very good because you will need a heat sink to cool the transistor an it wastes a lot of power as heat. A more efficient way to do it is by using PWM. The circuit is a bit more complex but you won't need a heat sink at all and you won't waste power as heat.
  5. SgtWookie


    Jul 17, 2007
    A potentiometer won't handle that kind of power, and would be very inefficient besides.

    You need a PWM circuit.

    One such circuit is here:
    You won't need the 1N4001 diode. Hook up your heater to the MOTOR+ and MOTOR- connection points.