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12V relay Question

Discussion in 'General Electronics Discussion' started by fastpcuser, Sep 12, 2012.

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  1. fastpcuser

    fastpcuser

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    Apr 8, 2012
    My Power supply is 12VDC and it runs 12VDC under load and no load, but I have relay that requires 12V to switch, but it runs trough protective 1N4001 diode and that drops the Voltage down to 11.3VDC and it won't switch the realy I can only hear clicking noise. so My question is if I switch to 9V relay can I still use 11VDC or will I burn the relay ? or is there a way to drop 2V some how ? I tried another diode or two but that does not really work. The load (pump) runs at 600mA.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    A 12V relay should have no problems switching at 11.3V. And you're supposed to hear a clicking sound.

    Check the specs of any relay you want to purchase. The specs will include a safe range of voltages (for your current relay, they should tell you if 11.3V is OK).

    How are you switching the relay? It may be that which is a problem. If you're using a transistor, do you have a diode *across* the relay coil? (reverse biased)
     
  3. fastpcuser

    fastpcuser

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    Apr 8, 2012
    it is driven with 2N2222 transistor right now I have 12VDC power supply which with no load runs at 15.4VDC and at the relay there is about 14.1 -2VDC and it runs fine with no problem. But if I put this other powersupply on which has only 11.3V at relay it just make clicking noise and won't switch. and Yes I have diode across the coil.
     
  4. fastpcuser

    fastpcuser

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    Apr 8, 2012
    runs fine on breadboard now but won right correctly on PCB
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Always check the specs.

    That relay should operate from 9V.

    Be aware that the 2N2222 will also drop some voltage. Measure the voltage across the coil of the relay and tell me what it is.

    Can you also measure across the normally open and normally closed contacts and tell me what happens?

    If you hear it click, then it's almost certainly switching. I wonder if you've connected the load across the NO and NC contacts rather than the common and NO (for example)
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I'd strongly suspect a wiring error to the contacts then.

    Does it click differently?
     
  7. fastpcuser

    fastpcuser

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    Apr 8, 2012
    not really , it just keeps clicking like it wants to switch, but then why does it work with other supply ?
     
  8. fastpcuser

    fastpcuser

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    Apr 8, 2012
    Ok I found it my error, I had it connected wrong, had common to No and Nc to my load. Thanks for your help
     
    Last edited: Sep 12, 2012
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