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24V supply for a 12V dc motor

  1. Oct 25, 2009 #1

    Can anyone help me to figure how to get 12V for the dc motor using 24V supply.
    I would like to use a 12V supply but that would mean some changes to the wiring.

    Instead of rewiring,I would like to just make do with the 24V supply.

    I will need a series resistor (ranging from 1k - 10k)so that I can control the current to the motor.Since the dc motor internal resistance is very small (approx 100ohms),putting them in series will not get me 12V.Putting another resistor in parrallel with the motor will probably require a very huge resistance.

    I thought of using zener diode in parallel with the dc motor but that will probably require the zener diode resistance to be greater than the motor coil so I can have most current going to the motor.

    Can anyone recommend any other solution to get 12V for the dc motor but at the same time a large current to goes to the motor?

    Thank you.
  2. jcsd
  3. Oct 25, 2009 #2


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    Science Advisor

    Hi Raymond.

    You need a 12 volt regulator. The type will depend on the motor current.

    12 V regulator.PNG
  4. Oct 25, 2009 #3
    Yes,thank you for sharing.But is there any other way to modify the circuit using the 24V supply?

    Instead of the 12V regulator,I can also use the 12V supply directly.But I wish to make use of the 24V supply so the wiring would be more organized with all motors input using 24V supply.

    Thank you.

    Edit:I think I will just use the 12V regulator.This solution will at least simplify the wirings a little bit compared to the direct 12V supply. Thank you.
    Last edited: Oct 25, 2009
  5. Oct 25, 2009 #4


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    Science Advisor

    You can use resistors if you are sure the motor will draw constant current.

    But why do that? Regulators are cheap and simple. Just measure your motor current at 12 volts under different load conditions and get a regulator that has plenty of current capability.
    Mount it on a heatsink.

    Just saw your edit. Good choice.

  6. Oct 25, 2009 #5
    ok,I will do that.Thank you for replying.
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