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Control 30 mA 12V relay with 2.4 mA 12V

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Discussion in 'General Electronics Discussion' started by poser, Jul 29, 2010.

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  1. Jul 29, 2010 #1
    poser

    poser

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    Jul 29, 2010
    Hi Everyone,

    I'm not really an electronics guy, but I'm trying to wire up a simple circuit to control my projector mount with the projector's trigger circuit. I have figured out most of it but ran into a small problem. The projector's trigger is 12V 2.4 mA and the relay I have is 12 V 30mA. I have gathered that I need a transistor to boost the current so that it can trigger the relay. What I don't understand is which transistor to buy, how to wire it, and what resistors and diodes I need (if any).

    Any help is appreciated.

    Thanks,

    Joe
     
  2. Aug 6, 2010 #2
    NickS

    NickS

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    Apr 6, 2010
    Sorry nobody has responded yet. This is a simple task. I looked up a relay with similar requirements to yours and it had a nominal DCR of 400 ohms so I represented it in the circuit below as a 400ohm resistor. All you do is place your relay coil in its place and away you go.

    S1 represents the 12V @ 2.4mA(max) coming from the projector. The transistor will only consume about 500uA of that.

    Good Luck
    -Nick-
     

    Attached Files:

  3. Aug 7, 2010 #3
    poser

    poser

    2
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    Jul 29, 2010
    Thanks!

    Great, thank you for the response. Very simple and easy to understand. I'll wire it up and see if it works! Thanks NickS.
     
  4. Aug 7, 2010 #4
    Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Thanks Nick.
    It slipped me by after I didn't have the time to make a proper reply the first time I read it. Sorry about that.
    Just remember to put the usual protective diode across the relay coil. I guess it goes without saying that you'll need a 12V power supply.
     
  5. Aug 9, 2010 #5
    NickS

    NickS

    367
    0
    Apr 6, 2010
    Sorry I forgot the didoe.
     
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