sensor triggering problem.

Discussion in 'The Projects Forum' started by reymund, Jan 5, 2010.

  1. reymund

    Thread Starter Member

    Sep 23, 2008
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    good day!,
    i was working with my household project that would activate a load from the relay, now my input is a sensor(lm324 comparator mode), and the output is then inverted through a inverter ic(to have a negative pulse), and the signal is send to the 555 timer ic which is in monostable one shot configuration. i was able to run it and calculated the desired timing output.

    Now i was not able to know if what IC is needed for the triggering will be like this:

    1). if the sensor is triggered, logic 1 will send and the circuit will be on, thus turning on the load.

    2). if the the sensor is triggered again, logic 1 will send to the circuit, thus turning off the load.

    these 2 are my concerns, anybody who knows what are the IC that are needed to add to my existing circuitry for me able to do this. i am not planning to use a microcontroller. TIA. i hoipe you guys can help me. thanks...
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Sounds like you need a toggle flip-flop, similar to 74C74. Connect not Q to data and every + input will cause output to change state.
     
  3. reymund

    Thread Starter Member

    Sep 23, 2008
    23
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    sir here is my schematic, where should i connect the toggle flip flop?.thanks[​IMG]
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Here are 2 choices, A & B. A keeps 555, but dumps it on 2nd pulse. Both edges of IC1A differentiated , leading + pulse sets FF, enabling 555, trailing edge pulse triggers 555. Second pulse resets FF, foreshortening its timing.
    B , first pulse sets FF, turning on load, second resets FF turning off load. Pulse need not to be differentiated. UCC V unknown, assumed to be +5.
     
  5. DigitalLogician

    New Member

    Dec 20, 2009
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  6. reymund

    Thread Starter Member

    Sep 23, 2008
    23
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    sir bernard what is the IC1 on your schematic?. is it the inverter or op amp?.
     
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    IC1A is the comparator from your print , outputting , hopefully, a square positive pulse.
     
  8. reymund

    Thread Starter Member

    Sep 23, 2008
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    [​IMG]


    sir i worked with this one, and it went ok so far, but the output on the 7474 ic is not stable enough, meaning when i pass my hand on the sensor the transistion from the output Q and Qbar is not clean, sometimes it the led indicator is still on the Q, but the led indicator lits for a few seconds and back again to Q, but when i turn off the light, the output is ok, the transition is good..


    and also, i have a have a problem on the triac, when there no input on the optocoupler, there is a voltage drop on the load( ac axial fan 220V rating) around 145VAC, why is it like this?, but when the sensor is triggered the output on the load is very good. thanks....
     
  9. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    74LS74N substituted for 74HC74N; FF Q & not Q over loaded, use invertors to isolate LEDs 2 &3 from ckt. Connect R & LED to +V & output. Drive photo coupler from invertor same as LEDs. Preset not shown connected to +V. R3 about 10K, C1 .1uF or larger if needed to reset FF at power turn on. For triac, short p 1&2 of OK1, check result. No change, remove OK1 & check.
     
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