Add propagation delay

Discussion in 'General Electronics Chat' started by magnet18, Jan 3, 2015.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Anyone know an easy way to add about 1/10th of a second delay to a digital logic line?

    I'm looking for a way to show the glitching when using a ripple adder that uses full adder blocks, just enough to bring the glitching to the human visible level

    google wasn't giving me any easy ways to ADD propagation delay :p

    Thanks!
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    An 8 bit shift register clocked at 1/80th of a second?
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Do you want to delay a pulse, or stretch a pulse?
     
  4. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    I developed digital a propagation delay circuit a while ago...
    What's the digital line's frequency?
     
  5. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    I'll keep that in mind, i think it would be a lot of registers for my application
    delay? i think both might work, posting schematic
    clock frequency range

    more detail about my idea, a ripple adder like the one below (ignore mode and flag stuff) will have a propagation delay in each adder module, that results in glitching of the numbers further down the line, the more significant the number, the longer it takes for the glitching to settle out (imagine the circuit is expanded to S6 or S8)

    I was thinking about making a display that uses this glitching effect to look cool, like a clock that gets it's output by adding 2 numbers, or just a demonstration piece with toggle switch inputs

    to see the glitching, I need to make the propagation delay noticeable, the easiest way seems to be to delay the signals coming out of the adder blocks somehow

    I could be overthinking it, an RC circuit might do, but I'll take a digital option if there is a reasonable one
    Capture.PNG
     
  6. toffee_pie

    Active Member

    Oct 31, 2009
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  7. Lestraveled

    Well-Known Member

    May 19, 2014
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    24,000 yards of RG-58 :D:D (just kidding.)

    I used a bunch of 74ls164 shift registers back in the 80s to generate synthetic range target. Very jittery.
     
    GopherT likes this.
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I'd go with the RC delay, followed by a couple of Schmitt inverters to clean up the pulse edges.
     
  9. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    I would need about 100000000 inverters to make a 1/10 second delay :D
    LOL, that would end up being a small clock hooked to a spool of wire bigger than my house, hahaha
    yea, I think the good ol RC is looking like the cheapest/easiest option :p

    Will post update eventually if the project gets off the ground, the semester is starting back up :p
     
  10. WBahn

    Moderator

    Mar 31, 2012
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    A pretty easy way to do it would be to use an MCU or FPGA and simply echo the input to the output after the desired delay.
     
  11. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    I've never touched an FPGA, it can handle delaying lots of inputs and outputs?

    What is one you would recommend looking into, I've been meaning for awhile to get familiar with them
     
  12. WBahn

    Moderator

    Mar 31, 2012
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    I don't have a specific recommendation for you since it has been a number of years since I've worked with an FPGA and most of the ones I did work with were mid-line units with lots of I/O. I don't know what the lower end of the scale is today, which is probably where you want to look to keep costs down. You might look at Digilent and see if one of their development boards would work for you -- and I think it probably would.
     
  13. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The Digilent Max32 board can sample up to 500k times per second and has lots of memory. I just made a little audio delay - echo. You may want to use the Microchip asm commands instead of the Arduino code as you have no (difficult) control of instruction timing with the Arduino code.
     
  14. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Thanks, I'll look into it!

    EDIT
    $50, that's probably why i've never messed with an FPGA :p
     
    Last edited: Jan 13, 2015
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