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converting 12 volts to 4 volts

Discussion in 'Misc Electronics' started by Locoaudio, May 29, 2008.

  1. Locoaudio

    Locoaudio Guest

    Hi
    I have a classic motorcycle and I have updated the old alternator to a
    Permanent Magnet Alternator,
    but the motorcycle has a starter safety relay ( which basically stops
    the starter motor from reengaging once the engine has started)
    which is activated by 4 volts from the old style alternator
    now i need something small rugged and vibration proof to step down
    the voltage from 12 volt to 4 volt
    any ideas
    Jamie
     
  2. GM

    GM Guest

    See the following which is for 12V to 3V

    http://www.coolcircuit.com/circuit/12v_to_3V/12V_to_3V.GIF

    I guess you have to find a zener diode that is about 4.7V and of course
    you should recalculate R1. Look @
    http://www.diodes.com/products/catalog/list.php?parent-id=9
     
  3. GM

    GM Guest

    See the following which is for 12V to 3V

    http://www.coolcircuit.com/circuit/12v_to_3V/12V_to_3V.GIF

    I guess you have to find a zener diode that is about 4.7V and of course
    you should recalculate R1. Look @
    http://www.diodes.com/products/catalog/list.php?parent-id=9
     
  4. Jamie

    Jamie Guest

    A resister?
    Need to know the coil resistance of the relay for proper calculations

    http://webpages.charter.net/jamie_5"
     
  5. S K Mandal

    S K Mandal Guest

    hello friend
    You can use voltage regulator LM7805 (NATIONAL Semiconductor/
    FIRCHILD) , so the output of the regulator will be 5Volts @ 500mA max.
    Then you can connect a diode or a resistor with a filter capacitor to
    drop further by 1Volt.
    Good Luck.

    REGARDS
    SUBIR KUMAR MANDAL
    SCIENTIST 'B'
    DRDO
     
  6. S K Mandal

    S K Mandal Guest

    YOU can also try LM317, adjustable voltage regulator, Aand to drive a
    relay you need 10mA to 20mA depending upon their types.
     
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