problem with relay

Discussion in 'The Projects Forum' started by lesin akbar, Dec 16, 2007.

  1. lesin akbar

    Thread Starter Active Member

    Dec 16, 2007
    30
    0
    i used a relay logic to give a back up power to my microcontroller when the main supply is removed. Now it is moving smoothly when the main supply is gone, as it provides the back up, but when the supply comes back the relay is vibrating instead of cutting off. what is the reason for this ? how can i solve it ?
     
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    Attach your schematic. Then the members can assist you.
     
  3. lesin akbar

    Thread Starter Active Member

    Dec 16, 2007
    30
    0
    i'll be sending the shematic soon
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    Wild guess: lack of a protection diode so the back emf generated by the coil when the relay shuts down triggers the driving IC again (if applicable). Happened to me with a 555 timer. After I removed the diode, the relay connected to the timer output started behaving like that.
     
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