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simple heater control

Discussion in 'The Projects Forum' started by LennieSmith, Jun 19, 2009.

  1. LennieSmith

    Thread Starter New Member

    Jun 19, 2009
    Hi everyone,
    I'm looking at making a really simple circuit which controls the speed of my cars heater. I'd like it to start at about 6 volts, and go to it's MAX speed of 12 volts with a potentiometer.

    I've had no problem using a voltage divider, but I also want to turn the heater off when the knob is turned all the way, and I have no idea how.

    I'm not sure if I can buy pots which have a 'switch' or not, but if I can't I was wondering if there was some other way (not super complicated) to turn it off, and vary the voltage.

    I don't know much about electronics, and almost everything I've read has confused me more :(. Any help would be greatly appreciated,

  2. franzschluter

    Active Member

    Jun 1, 2009
    Well you must first explain how your car heater works?

    Usually a car heater gets its heat from the radiator fluid. Then passes through some thermal exchanger similar to an evaporator unit. A fan is located there that blows air.. The other side will be hot air coming out.

    So what do you want to regulate? The fan speed? If this is the case.. You must do it with PWM. Varying voltage with a potentiometer directly is hard specially with 1 amp load. I think the potentiometer will burn. It must be done with a different approach..

    Look in this forum for PWM FAN SPEED. There are also lots of schematics on this available on the net.
  3. LennieSmith

    Thread Starter New Member

    Jun 19, 2009
    Well my heater has a simple in/out tube for radiator fluid, and a +ve and -ve terminal. The water provides the heat, and the car battery powers the fan which blows the air out the top. The car came stock as 6volts, so the heater is a tad slow, but after upgrading to 12volts it's much faster - so the speed is varied by the voltage. Incase your wondering, its a 'warmaride' heater, and the car is an old Holden FX so it didn't come stock. Anyway, I'll look up PWN Fan speed as a backup, as this morning I managed to find an old control knob for it, which is basically a potentiometer with an off switch when the knob is fully turned - exactly what I wanted. Hopefully it works, and doesn't burn at 12 volts (hopefully). Thanks anyway, I'll look it up and use it as a backup if I smell smoke :p