How to make a toggle latch to drive relay?

Discussion in 'General Electronics Chat' started by Merlysys, Nov 29, 2013.

  1. Merlysys

    Thread Starter New Member

    Nov 17, 2013
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    I am returning to electronics after several decades of absence so I am fuzzy about how to go about this, please help design a circuit.

    Need a circuit that will toggle/latch and drive a mechanical relay. 24VDC/2.7Kohm coil
    The input to this desired circuit will come from the output of a PT2272-L4 IC decoder shown. Switch bounce is already taken care of so the input to the required circuit will just be a rising edge.
    So on each rising edge(input) ---- the output is to latch/delatch and drive a normally open mechanical relay.
    So on one rising edge the relay will become closed and stay closed, on the next rising edge relay opens and stays open.
    I like to build it around these parts if possible.
    http://www.b2cqshop.com/ebayphoto/Q00915983-2.jpg

    What do you think of the circuit below? I got it from here
    http://www.youtube.com/watch?v=vNpryyroaWQ
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Two relays can be set up as a flip flop, the relays latch alternately on the same pulse.
    Max.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Lots of options. Google: Push on push off circuit

    Attached is one I always thought was interesting.

    Ken
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I don't see how that will be compatible with the circuit you show, which relies on C1 being alternately charged and discharged :(
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It sounds like the OP wants a single PB to toggle (flip-flop) a relay, I have used a circuit with two relays or the one shown in the post before should perform the same function?
    Toggle on each push of the button?
    Just that the SS design would be replaced by relays.
    Max.
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    You are right. I went back and read the requirements.

    Ken
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If a PT2272-M4 (momentary type) was used a 2n7000 on the output and the 2n7000 could replace the P.B. switch on the PDF.
    Max.
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    This should do the job, using components in your preferred set. Any logic-level pulse rising edge will toggle the circuit:-

    Edit: Change R3,R7,R8 to 18k to reduce transistor reverse Vbe and relay 'off' current.
     
    Last edited: Nov 30, 2013
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    If you are using mechanical anyway and speed isn't an issue.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Doesn't the output of the L4 version alternatively latch/unlatch?
    As opposed to the M4.
    Max.
     
  11. Merlysys

    Thread Starter New Member

    Nov 17, 2013
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    Right. But I have the M4 version which is the momentary type
    ........mistakenly put L4 in the diagram, sorry.
     
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