Relay Coil Rating

Discussion in 'General Electronics Chat' started by vindicate, Aug 5, 2009.

  1. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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    I was looking at a 5v coil relay to switch 120VAC. The nominal current was listed as 200mA. So is nominal current the max current it needs? The minimum current it needs? Or what? How does that work? Does it draw what it needs?

    Could I give it 6 or 7 volts but with a resistor inline to limit the current?
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Can you post a link to that particular relay?

    Ken
     
  3. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Just place a diode like a 1N4000 in series to drop the excess - for 7 volts use 2. Relays are not sensitive to overvoltages, but the coil will heat and possibly fail.
     
  5. mik3

    Senior Member

    Feb 4, 2008
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    Yes, it will draw 200mA.

    You can use a resistor with an appropriate value to limit the current if you drive it with higher voltages.
     
  6. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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    So with the 5v 200mA example I gave I could use a 10v supply and a 25 ohm resistor rated for 1watt?
     
  7. mik3

    Senior Member

    Feb 4, 2008
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    Yes you can!
     
  8. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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    Excellent. Thanks you.

    Last question. Pull In Voltage. It's listed at 75% or less of nominal voltage. So If I have a 5V coil, could I technically power it with 4V and it would work fine?
     
  9. mik3

    Senior Member

    Feb 4, 2008
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    Yes you can but it is better to power it with the nominal voltage.
     
  10. vindicate

    Thread Starter Active Member

    Jul 9, 2009
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    Alright, thanks for everything :)
     
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