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How to detect a plug is connected to socket

Discussion in 'General Electronics Discussion' started by bobdxcool, Apr 3, 2015.

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  1. bobdxcool

    bobdxcool

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    Mar 9, 2012
    I have a plug and socket. Before I turn on power supply from a contactor, I need to detect if the plug is connected to the socket via a microcontroller. Any ideas on how to do this ?
     
  2. BobK

    BobK

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    Jan 5, 2010
    Are you talking about a mains power socket and plug?

    Bob
     
  3. bobdxcool

    bobdxcool

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    Mar 9, 2012
    The Plug I am using is

    [​IMG]

    The socket I am using is:

    [​IMG]

    All the four pins of both socket and plug are connected to neutral, ground and (120v) ac lines.

    The issue is that all the four pins of both socket and plug are connected to neutral, ground and (120v) ac lines. Please see the pictures posted above. So, there are no other pins left to use. I was thinking of using a magnet near the socket and a hall sensor stuffed (Not a safe idea I guess) somewhere near the plug. Any better ideas ?
     
  4. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Tell us what your trying to do, and why you need verify the plug is attached.
    Perhaps the current can be detected by a ct downstream?
    Also curious about where your located to better understand voltage configuration.
     
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Can you check for continuity between NEUTRAL and GROUND in the plug? Should be continuity when plug is mated to receptacle, no continuity when plug is disconnected from receptacle.
     
  6. bobdxcool

    bobdxcool

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    Mar 9, 2012
    USA. Need to turn on power supply to my device only after plug is detected inside the socket.
     
  7. bobdxcool

    bobdxcool

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    Mar 9, 2012
    Thank you. Will check. Can you explain why there would be continuity between neutral and ground when plug is connected to the socket ? If I am not wrong, wont there already be continuity between neutral and ground coming from main power supply in USA ?

    Is there any way of detecting whether plug is connected to socket on the socket side (Blue socket, pic posted above) . Because it will be difficult to access the plug (yellow one in pic above) in my application

    The way it is connected now that the blue socket in picture above (female) is connected to the mains power supply. One pin is connected to neutral, another to ground, and the other two to two in phase 120v lines. The yellow plug is connected internally to 120volt equipments
     
    Last edited: Apr 3, 2015
  8. BobK

    BobK

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    I thought you were going to use the contactor to provide power to the plug. Presumably, then, when the contactor is off, there is no power to the plug. However, I would think that checking for continuity would be dangerous since if the contactor is turned on when you have an additional circuit connected to check for continuity you are going to put 120V into that circuit. You would want to use another relay as a failsafe such that the contactor could not be energized when the to connect the continuity check device was connected. I.e. a DPDT relay that connects the continuity test probes in the on position and the contactor coil only in the off position.

    Bob
     
  9. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    You keep alternating your use of "plug" and "socket". From your OP, the blue female connector is a PLUG and the yellow male connector is a SOCKET. Presumably, the PLUG will be energized by a contactor eventually. However, whether the contactor is energized (closed) or not, there should always be continuity between the NEUTRAL and GROUND in the blue PLUG. Presumably, the yellow SOCKET is the equipment to be powered by the blue PLUG. There should be no continuity between the yellow SOCKET NEUTRAL and GROUND connections if it is wired properly to the equipment. This is what I was suggesting that you measure, but if those terminals are not accessible then Plan B is necessary.

    There are many Plan Bs that will work. Your idea of a small magnet and a Hall sensor mounted nearby would work. Or a small magnet and a reed switch. Or a small microswitch glued near the yellow SOCKET and actuated by the blue PLUG body. Or, my favorite, a really tiny CCD camera with image recognition software and infrared LED illumination to keep and "eye" on the yellow SOCKET and enable the contactor when the blue PLUG is inserted. There may be other Plan B solutions that will work.
     
  10. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Why? What is your device?
     
  11. Tha fios agaibh

    Tha fios agaibh

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    725
    Aug 11, 2014
    hevans1944 likes this.
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