Series Time Delay circuit question

Discussion in 'The Projects Forum' started by zcream, Feb 21, 2009.

  1. zcream

    Thread Starter Member

    Feb 21, 2009
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    Hi! I am connecting 30 devices in series. I am trying to delay the input pulse 4-10ms for each device. Thus Device 1 is 4ms delayed from Device 0, Device 2 is 8ms delayed from Device 0 etc.

    Since the delay is small enough and does not have to be precise I am thinking of using a simple RC delay.
    However, I am unsure what happens when you connect 30 RC delay circuits in series.
    There is probably feedback, and due to capacitances in parallel the net capacitance will reduce..
    How can I add a "buffer" so that once a signal progresses from Device 0 to 1 to 2, it is unaffected by the R and C values "behind" it ??
    I hope its clear - I can add more details if its not..

    In summary, a circuit where various points in series need an increasing time delay from the origin..
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    What does your input pulse look like? Do you need to have fast risetimes at each delay point?
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I made a 3 phase square wave generator using 3 inverters with a 10k from output to input, and a .1μF to ground, with output of 3rd going back to the first. It ran around 400Hz, each is 50% duty 120 degrees apart. Output wasn't exactly square, but didn't need to be for the application.

    Adding an additional buffer between input (R/C) and output would give a clean square wave at the inverter output if you use Schmidt Trigger inverters (74xx14 or 40106).
     
  4. zcream

    Thread Starter Member

    Feb 21, 2009
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    Hi Ron. I dont need fast rise times - the trigger is essentially a Voltage rise upto 3V.
    I am using a 3.6V Lithium battery for sending the pulse..

     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    How precise does your delay have to be?
    How wide is the pulse?
    Does the pulse repeat?
    If so, what is the frequency (repetition rate)?
     
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