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Car 12v to 4.5v resistor circuit needed for low current device

Discussion in 'Beginner Electronics' started by [email protected], Nov 1, 2005.

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  1. Guest

    What resistor circuit is needed for a low current trafic alert device
    which can be plugged into the courtesy light?
    The traffic alert normally runs on 3 AAA batteries, but a terminal has
    corroded off... }:-(

    Happy with a soldering iron and vero board

    cheers
    Richard
     
  2. Harold Ryan

    Harold Ryan Guest

    Attach a 1 kohm resistor between 12 volts and the device you want to power.
    Measure the voltage at the device. If the voltage is below, decrease the
    resistor until you obtain 4.5 volts. Now add a 4.5 volt zener diode because
    the vehicle voltage can vary from 7 up to 15 volts.

    Harold
     
  3. gladholm

    gladholm Guest

    Thanks for that and other info have helped cheers
     
  4. gladholm

    gladholm Guest

    Thanks for that and other info have helped cheers
     
  5. Rich Grise

    Rich Grise Guest

    You shouldn't need much:
    http://www.radioshack.com/product/i...tId=2103679&kw=dc+power+adapter&tab=techSpecs

    Or, you could use a hash choke, a transzorb, and a regulator to do pretty
    much the same thing. ;-)

    Cheers!
    Rich
     
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