designing a combination of delay timer and relay

Discussion in 'The Projects Forum' started by abhishek_mitra, Oct 10, 2009.

  1. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    hi !!
    i am new user 2 this website..i found this very interesting and a great place for all curious guys like us.

    can anybody please help me out in designing a circuit using 555 timer that will generate a desired time delay(time delay that can be adjusted by the user).this timer will get activated upon receiving a particular signal from a pre-device and start counting,after the desired time delay it will actuate a relay from NC to NO..

    i will be very gr8ful 2 u if kindly help me out

    thanx n regrds 2 u all
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    At top of page with All About CIRCUITS, upper right side is a white box , put 555 in. Check esp. Bill Marsdens articles. Put a schematic together, and post for review. You'll need 2 555's or a 556, one for delay, and cap. coupled to 2nd as relay driver.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Are you wanting the relay to be NC before the trigger?

    You can combine this

    555 Monostable

    with this

    [​IMG]
     
  4. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    yes i want the relay to be in NC position before triggering..
    should i use the 555 in monostable mode??
     
  5. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    sir this circuit will actuate the relay from NC to NO,but what more can be done to switch the relay back to NC??how will this circuit work,can u please help me out sir??
     
  6. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    abhishek
    im a bit new too, but i can help with the easy bits,
    when the monostable times out, the relay will return to its original state- nc.
    how are you triggering the monostable can it be triggered directly with a pushbutton,
    or is it triggered by a pulse from a previous circuit,?

    can i just ask the experts about the 555 as a buffer, the standard 555 can handle 200ma- most relays are i think about half this.does the load affect the timer function.?
     
  7. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    surge current?
     
  8. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    well sir i am also abit confused for the triggering mechanism.actually what i want 2 design is a circuit with a timer that will start counting the time after it is triggered by another pre-device's o/p.as soon as the timer times out it will actuate the relay from NC to NO.

    after this when the timer is reset the relay will come back to its original position i.e back to NC.
    now for this type of circuit will the 555 as monostable work or do i need to adapt some other circuitry?

    i have tried to workout logically the above schematic given by Sir. Bill Marsden,but i am confused for the triggering part and bringing the relay back to NC.....please help me out
    it would be a great help if anybody can attach the schematic
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    See the attached schematic.

    If you need more than 10 seconds, increase the size of C1.
     
  10. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    thnx a lot sir for d schematic.i will try this out as soon as possible...
     
  11. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    sir will this circuit work to bring back the relay to NC after the reset pin is triggered?
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    After the time has expired, the NC contacts will again close.
     
  13. abhishek_mitra

    Thread Starter New Member

    Oct 10, 2009
    7
    0
    sir i was working out few of my ideas in designing the desired circuit of mine.i got this idea of cascading 2 555 timers.1st will be an Astable mode 555 timer and 2nd would be a Monostable mode.

    when the pre-device triggers the astable multivibrator;it'll start counting the time,the output of the 1st timer will be fed to a comparator with reference voltage of 0V,as soon as the 1st timer times out the comparator will give a positive output that will fed to the 2nd 555 timer(monostable multivibrator) at the trigger pin;this will activate the monostable MV and as a result the relay connected to the 2nd 555 timer will get actuated from NC to NO.

    now while bringing the relay back to NC,i'll apply some negative pulse(greater than the +Vcc connected to the RESET pin) at the RESET pin of both the 555 timer.

    the above idea just came to me while i was trying to workout the various ways i can design this circuit.this is based on my theoritical knowledge and logical reasoning.i don't know until now whether this way it would be possible or not; but still i m trying my best..

    if anyone could help me then it would be a great help 4 me...
     
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