Need help with a relay

Discussion in 'The Projects Forum' started by Falven, Feb 27, 2010.

  1. Falven

    Thread Starter New Member

    Feb 27, 2010
    15
    0
    Hey guys,
    So I bought a 12vdc coil relay by accident, when in fact i need a 4-5vdc relay to use with my arduino ( arduino.cc ), is there any way I could make this work?

    Thanks,
    -Falven
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you have a 12v supply available in your application, you could switch the ground side of the coil with an N-ch logic-level MOSFET or an NPN transistor, with a 470 Ohm resistor on the base.

    Make sure to use a diode across the relay coil, or the coil current (reverse EMF) will blast the MOSFET/transistor when the Arduino shuts it off. The cathode of the diode (banded end) goes towards +12v. Any 1N400x series diode should work fine.
     
  3. Falven

    Thread Starter New Member

    Feb 27, 2010
    15
    0
    Thanks a ton, trying this now, will post back :)
     
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