off Relay after 3 second Timer

Discussion in 'The Projects Forum' started by aghaarash, Oct 13, 2011.

  1. aghaarash

    Thread Starter New Member

    Oct 11, 2011
    4
    0
    Hi guys. I want a circuit for relay which can turn off the relay after 3 second and it doesn`t turn off the relay if we reset the circuit or what ever to fresh this 3 second. if no action take place in 3 second then it turns off the relay.

    I really appreciate if some help me in this situation.
    Regards
    Arash
     
  2. #12

    Expert

    Nov 30, 2010
    16,278
    6,791
    Power must be off for 3 seconds before the relay turns off, Right? Relay "on" persist? Which relay? Volts, current, ohms of coil?
     
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  3. maxthestork

    New Member

    Oct 13, 2011
    13
    1
    I think I can see a solution for your system using a 555 timer for the timing funcion and a latching relay like the Omron G6HK-2-DC5.

    You would set the relay when you turn on the power with a one shot action like a push button or a one shot timer function (again from a 555).

    A separate timing circuit from a 555 would handle the reset after 3 seconds. There is a section in the datasheet that describes a sequential timer on page 15 of the datasheet.

    cheers
    Peter
     
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  4. aghaarash

    Thread Starter New Member

    Oct 11, 2011
    4
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    dear peter

    I need a circuit that start counting for 3 sec and if there is no action in 3 sec it turn off the relay but if any action take place in this time a timer restart and count again. but I dont think 555 can do this. if you think I am wrong please let me know.

    Regards
    Arash
     
  5. aghaarash

    Thread Starter New Member

    Oct 11, 2011
    4
    0
    I explain my situation again. it doesnt matter what is relay just a timer
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    I think you need a "retriggerable monostable" flip-flop. What's "any action take place"?...a voltage change?...a switch closure?...??? Whether or not the circuit can directly drive a relay depends on the relay you are using. What voltage do you intend to use to power this circuit/relay?

    Ken
     
  7. aghaarash

    Thread Starter New Member

    Oct 11, 2011
    4
    0
    It can works with 12Volt and any action means : reset.

    thanks
     
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    1,393
    Sounds like an easy job for a microcontroller such as the PICAXE 08M2 (less than $3.00). The programming software is free, but one needs a programming cable; a serial cable can be made, but a USB cable is about $30.

    The AXE-021 is a project board that could be used; possibly the relay could be mounted on the board. http://www.phanderson.com/picaxe/
     
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  9. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    230
    12V, OK. Reset how?...by what? It might be easier if you would explain what you are trying to do, not just a 3 second timing circuit.

    Ken
     
  10. #12

    Expert

    Nov 30, 2010
    16,278
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    This can be done very simply in analog IF you tell what the load is. The only way to keep a load powered for 3 seconds after the 12 volts is off, is to store enough energy to power the load for 3 seconds.

    What load?

    You don't say.
     
  11. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
    dare it be as simple as this or am I misreading the OP's request?

    [​IMG]
    or perhaps we are to sense a load applied or removed from an external circuit?

    and how exact does the 3 seconds have to be?






    ..
     
    Last edited: Oct 15, 2011
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