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Help to identify relay pins

Discussion in 'General Electronics Discussion' started by Djsarkar, Nov 3, 2020.

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  1. Djsarkar

    Djsarkar

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    Jul 27, 2020
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    First indication of a working relay: Does it click when power is applied to the coil?
     
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  3. dave9

    dave9

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    Mar 5, 2017
    Looking at the datasheet, you should measure approximately 150ohms on the two coil pins with a multimeter.

    Without powering the coil, you should measure almost zero ohms between the common pin and the normally closed. Powering the coil you should measure infinite resistance between these two and almost zero between the common pin and normally open, and of course you should measure 5V on the normally open to the LED if 5V is connected to the common pin.

    Have you tried it without the relay, providing 5V to the resistor and LED in series? Maybe the LED is bad.
     
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  4. Djsarkar

    Djsarkar

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    Jul 27, 2020
    Hi
    Yes I get click when 12v dc power is applied to the coil of relay. There is no fault with led. I have tested and it woks fine
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    Well then, show your wiring......
    You do realise you will have only 3 mA flowing with a standard LED and the 1k resistor...??
     
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  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Your connection looks right. Try the other contact (NC). The relay should work inverse: relay on = LED off and vice versa.
    One issue with this relay could be the relay contacts. This is a power relay meant to drive high current. The contact material is a silver alloy. Silver alloys will corrode over time, building a non-conductive layer of oxide over the contact. With high power loads this is not an issue as the oxide will be removed with every switching cycle due to the high current. A low load such as your LED may not be able to overcome the oxide. Try a high-power load instead of the LED to see whether this "cleans" the contacts.
    Here's some background reading on this effect.
     
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  7. Djsarkar

    Djsarkar

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    Jul 27, 2020
    Thanks there was bad cable connection so I have replaced cable and now relay is working fine with led
     
    narkeleptk likes this.
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