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Relay to switch a relay?

Discussion in 'General Electronics Discussion' started by Alec Hayward, May 3, 2016.

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  1. Alec Hayward

    Alec Hayward

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    Jan 22, 2016
    Hi, is it possible to switch a relay with a relay? I have a RF module from ebay which uses a DC 10A relay, but I need a 25A relay. The tracks on cheaply made boards can break easily if modified, so I was hoping to tie the output of a relay to switch the coil of a bigger relay?

    Hope you understand
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Yes. You can switch a bigger relay with the on board relay.

    Bob
     
    HellasTechn and Alec Hayward like this.
  3. Alec Hayward

    Alec Hayward

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    Jan 22, 2016
    Great thanks bob! I know exactly how to wire it all up
     
  4. HellasTechn

    HellasTechn

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    Apr 14, 2013
    Yes you can. Why not ?

    Just check if you need diodes in parallel with the relay's coil.

    i doubt you do though.
     
  5. Alec Hayward

    Alec Hayward

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    Jan 22, 2016
    Hello again, my parts came from eBay. But my second relay isn't working. I connected 12v to the comms on the first relay.

    Then on the NO I connected the coil of the second relay then too gnd. However it is not working. =( please help
     
  6. davenn

    davenn Moderator

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    Sep 5, 2009
    sounds like you made a wiring error

    is the second relay coil also 12V DC ?

    I will draw a cct
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    dual relay.GIF

    The first relay, transistor and resistor is what already exists on your board
    or something similar to that
     
  8. Alec Hayward

    Alec Hayward

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    Jan 22, 2016
    Yes this is how I connected it. I even checked the datasheet for my additional relay. So I knew which one was the coil.

    I haven't used a diode for second relay.
     
  9. Alec Hayward

    Alec Hayward

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    Jan 22, 2016
    I will double check everything is connected to NO
     
  10. Alec Hayward

    Alec Hayward

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    Jan 22, 2016
    Everything is connected properly? Damaged relay?
     
  11. davenn

    davenn Moderator

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    1,941
    Sep 5, 2009
    not critically important, but would be best to use one

    OK maybe show us a pic of your construction so we can check it
    make sure you label COM and NO contacts

    also you didn't specifically answer my Q

    Dave
     
  12. Omey Cool

    Omey Cool

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    May 30, 2016
    Please do check if the voltage provided by circuit/board is enough to drive the relay. you know you cannot operate a 12 v relay with 5v supply.
     
  13. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    This the OP has done:
    and a related questuin has been asked before:
    @Omey Cool : You're welcome to contribute to this forum, but please read the full thread before posting replies that do not fit the issue at hand well (cf. your post in the thread 'LED monitoring')
     
    davenn likes this.
  14. Omey Cool

    Omey Cool

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    May 30, 2016
    I was having same problem and that was a simple issue of power supply. Thats why i suggested to check supply.

    And i am pretty new here! :p
    Will do better next time.
    Thx
     
  15. DatLe

    DatLe

    15
    1
    May 31, 2016
    Hi, I draw not good. ^^
    Please re-check new 25A relay power input for relay coil.
    [​IMG]
     
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