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Which diode to use across relay coil contacts

Discussion in 'Electronic Basics' started by Harry Muscle, Dec 23, 2003.

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  1. Harry Muscle

    Harry Muscle Guest

    I'm putting together a circuit that calls for a diode across the relay
    coils. However, it doesn't specify which one to use. I'm using a 12V relay
    which draws 0.045A (265 ohm coil). Could someone help me out in choosing
    the best diode for the job.

  2. CFoley1064

    CFoley1064 Guest

    I'm putting together a circuit that calls for a diode across the relay
    Generally, the diode specified should be twice the voltage across the relay
    when it's on, and a surge current rating at least that of the relay current.
    To be conservative, choose a diode with forward current rating at least that of
    the relay. That gives you a minimum diode spec of V(r) > 24V, and I(fmax) >
    45mA. That would lead you to a 1N914 or 1N4148 as a first choice, but I'm
    superstitious and never use those for anything other than reed relays. I'd use
    a 1N4001 or 1N4002.

    Good luck
  3. Or go to the 1N4007 diode. its rated at 1000 PIV, and will replace
    any of the others in the 1N4001-1N4007 series. It costs the same as the
    1N4001, and you only need to stock one part instead of three or four.
    2 days!

    Michael A. Terrell
    Central Florida
  4. Chaos Master

    Chaos Master Guest

    In reply to a radio transmission from Harry Muscle([email protected]) , located at Mars:
    I've used the 1N4007. It's rated at 1000 PIV so it will replace any other in the
    1N400x series.
  5. Use the Harry Muscle kind, a 1N4002 Rectifier.

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