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Troubleshooting: Why the normally closed and normally open pin in my relay is shorted internally?

Discussion in 'General Electronics Discussion' started by Paul Saha, Jul 18, 2016.

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  1. Paul Saha

    Paul Saha

    42
    1
    Jul 7, 2016
    Did I do anything wrong with the relay or is it a manufacturing defect?
    I have detected this through multi-meter and it shows internal connectivity between the pins.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,778
    2,433
    Nov 17, 2011
    Both possibilities exist.
    You'll have to open the relay and inspect the contacts to find out why they are shorted.

    Does the short dissappear when you knock hard against the relay body?
    Are you sure to measure between the right pins?
     
    Paul Saha likes this.
  3. BobK

    BobK

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    Jan 5, 2010
    Another possibility is that you have misidentified the pins.

    Bob
     
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  4. Minder

    Minder

    3,029
    641
    Apr 24, 2015
    Another is if the relay has been used and the N.O. has welded to the common, this then shorts all three contacts.
    M.
    edit: make that N.O.
     
    Last edited: Jul 19, 2016
    Paul Saha likes this.
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    The N.O and N.C. contacts are normally physically separated by an air-gap with the movable common contact in between. To have continuity between a pair of N.O. and N.C. contacts requires that both the N.O. contact and the N.C. contact be "welded" to the common contact across the air gap! That condition is likely to be fairly obvious upon inspection of the relay, and there is probably no way to "fix" it. However, I suspect you are not measuring what you think you are measuring. Try measuring again with another relay of the same type and report back here with the results. Also, a model number and a pin-out of the suspect relay would help us identify what appears to be wrong. Show us these and explain which pins you are using to measure continuity between.
     
    Paul Saha, davenn and Harald Kapp like this.
  6. Paul Saha

    Paul Saha

    42
    1
    Jul 7, 2016
    Alright I got it. Thanks a lot!
     
  7. BobK

    BobK

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    Jan 5, 2010
    Care to clue us in?

    Bob
     
  8. Paul Saha

    Paul Saha

    42
    1
    Jul 7, 2016
    I misjudged the pins. I came to know only after looking at the datasheet.
    Not all relays have same pin configuration.
    Thanks again!
     
  9. Minder

    Minder

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    Apr 24, 2015
    If in doubt, read the instructions!;)
    M.
     
    Paul Saha likes this.
  10. hevans1944

    hevans1944 Hop - AC8NS

    4,547
    2,122
    Jun 21, 2012
    Always read and understand the datasheet for every component in a project before proceeding. From discussion on another thread you started, may we assume the diagram below represents the relay you are trying to use?
    upload_2016-7-19_17-11-56.png
     
    Paul Saha likes this.
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