relay circuit diagram

Discussion in 'The Projects Forum' started by sajelectric, Aug 19, 2011.

  1. sajelectric

    Thread Starter New Member

    Aug 19, 2011
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    I need to operate a 12v d.c pump and a fan using a 12v50ma relay by the open collector signal from a power supply. Can somebody send me a circuit.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    It's not clear what you want. A DC-power supply has a plus pole and a minus pole. You certainly mean a component with an open collector output that is somehow triggered/switched on, right?

    How is it triggered? If by a switch your circuit could be in it's simplest form an NPN transistor with switched base current, which allows you to control the emitter/collector current. The relay would then be connected from plus to the collector. Is that what you want? http://terpconnect.umd.edu/~toh/ElectroSim/relay.html
     
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
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    [​IMG]

    Here's one............................of a million!
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    5v/500 Ohms means that the LM339 would have to sink 10mA; where it may only be able to sink 6mA. It might work, but I wouldn't guarantee it.

    An LM311 would be a better choice.
     
  5. sajelectric

    Thread Starter New Member

    Aug 19, 2011
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    thanks for your response.
    Here I have a power supply unit which is programmable type and supply power to an heating element. simultaniously i need to start my 12v cooling pump using a relay.
    4 wires are available from the power supply.2 main lines and 2 signal lines. Hope one relay only is enough to start the pump.Please give me the suggestions and circuit.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    You really are not giving us any helpful information.

    We don't know how much current your 12v pump needs.
    We don't know how much current your fan needs.
    We don't know how much current you have available.
    "2 main lines and 2 signal lines" really does not tell us much; we would have to simply guess. Are the two signal lines for remote voltage sensing? What voltage and current does the power supply output?

    And why do you need to use a relay?
     
  7. sajelectric

    Thread Starter New Member

    Aug 19, 2011
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    its a 12v 3amps power source.
    pump drags around 2amps and fan 0.8amps.
    relay needed to automatically operate the pump and fan.(realy coil should be 50ma.)
    Hope you can help me with this info.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    OK then,
    Is your open collector current sink of 50mA enough to energize the relay that you have selected? The relay contacts must be rated for at least 3A at 12v, and the coil should have a resistance of 250 Ohms or more. Many automotive relays will be suitable for this application.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Here is a schematic for you:

    [​IMG]
     
    sajelectric likes this.
  10. iONic

    AAC Fanatic!

    Nov 16, 2007
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    SGT. I was being facetious, kinda mead I guess. He wanted a relay circuit so I gave him one. Since there was almost no supporting information as to specific requirements I just googled and posted a "relay circuit!"
     
  11. sajelectric

    Thread Starter New Member

    Aug 19, 2011
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    Hi,
    Yes my open collector signal is enough to handle 50ma.
    can you please explain O.C in the above given circuit.
     
  12. sajelectric

    Thread Starter New Member

    Aug 19, 2011
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    Useful ckt.
    Could you add an EMI filter with the circuit

    Thanks
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    There wasn't room to type "open collector" in the connector, so I typed O. C.
    instead.
     
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