Help with pulse "delay"

Discussion in 'General Electronics Chat' started by kurtruk, Dec 24, 2012.

  1. kurtruk

    Thread Starter Member

    Aug 26, 2012
    140
    6
    So I built this circuit on the breadboard and it worked. I then removed the connection to ground and it still worked. I even removed the capacitor and resistor and it still worked.

    What I am trying to do is lengthen the pulse by a ms or so.

    My questions are:
    1st is my circuit to delay/lengthen the signal right?
    2nd Is it working even without the capacitor and resistor because of the stray capacitance of the wires and breadboard?
    3rd Is the connection to ground necessary?
    Do I even need this because the output has to go through a OR gate which will delay it some?
     
    Last edited: Dec 24, 2012
  2. MrChips

    Moderator

    Oct 2, 2009
    12,451
    3,370
    1) No.
    2) No.
    3) No/Yes

    Your circuit is not correct, not as a ms pulse stretcher.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Show us some more of the circuit, including where the input comes from and where the outout goes.
     
  4. kurtruk

    Thread Starter Member

    Aug 26, 2012
    140
    6
    Could you elaborate more? I thought that when the input is high the cap will charge then when the input is low it will discharge. Do I even need to delay it because of the processing time of the OR gate.


    In response to Ron, it is part of a timer circuit that after it reaches a certain point it resets back to 1.

    Note the reset is detected on the rising edge while the counter detects on the falling edge, so is any of this even necessary???
     
    Last edited: Dec 25, 2012
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I asked you to:
    I'm sorry, but your answer does not do that. If you want help, you need to post a schematic. If you don't know how to do that, ask.
     
  6. kurtruk

    Thread Starter Member

    Aug 26, 2012
    140
    6
    Purpose: to count from 1-12 (1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5...)

    Both I have built on a breadboard and both work. I just need to make sure that the better/simpler one will work on a pcb.

    Idea one:At 13 the ANDs go high causing the counters to reset and the capacitor to charge. The ANDs then go low and the capacitor discharges causing the counter to advance to one.

    Idea two: The proccesing time of the OR gate is enough to cause the pulse to advance to one to be after the reset is high.

    So which one is better? I have very little faith that my capacitor-resistor setup is right.

    any help at all is greatly appreciated as I attempt to teach myself electronics.:)

    p.s. my version of Eagle is 6.3.0
     
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