Pulse Signals

Discussion in 'The Projects Forum' started by aaron12345, Dec 11, 2013.

  1. aaron12345

    Thread Starter New Member

    Dec 11, 2013
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    All,

    Ive been tasked with programming a Direct Logic 05 PLC to control parts built on an endformer. In the logic, I need to send a single pulse to a camera to select which job the camera is to perform. Specifically, when in job change mode, the camera will detect a pulse, and that will tell it to select job 1. Same goes for 2 pulses = job 2, and so on. My problem is that I have never seen how to make multiple pulses in a rung.
    For job one, I am using a one shot relay to send the signal. Unfortunately, I can't figure out how to do multiple pulses.
    If someone could shine some light on this, that would be great. Thanks in advance.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If I interpret right, you are using one input pulse but want to differentiate between modes or jobs using multiple counts from one pulse?
    You could use a counter and as long as the pulses occur at a fixed repetitive rate, then validate the count by detecting a time period after the last pulse using a timer set for a period longer that the interval between pulses.
    Anything shorter, resets the timer.
    Max.
     
  3. aaron12345

    Thread Starter New Member

    Dec 11, 2013
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    To specify, the camera will understand which program mode it needs to be in by receiving a specified amount of pulses. (I.e. 1 pulse = mode 1, 2 pulses = mode 2, etc.) Consequently, I need to figure out how to program specific amounts of pulses in the ladder logic. I thought I might be able to do multiple one shot coils, but that doesn't work.

    Is there a coil that sends pulse signals? If such an item existed, I could add a counter to the rung and use it to stop the pulses after receiving a specified limit. Any thoughts?

    Thanks for all the information.
     
  4. aaron12345

    Thread Starter New Member

    Dec 11, 2013
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    I think what I am looking for, is how do I send two, and three pulses to a coil? Thats all. I determined that I could do a single pulse with a one shot, but I am confused on how to do two and three pulses.

    Thanks for everyone's help and advice.
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    If you can draw the waveform to show what you need, it would be helpful for the discussing.
     
    aaron12345 likes this.
  6. inwo

    Well-Known Member

    Nov 7, 2013
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    Is the single pulse from the one-shot long enough?

    It seems you would need a longer pulse.

    The plcs that I use have a free running clock that you could access for pulses. 50% duty cycles.

    Else use two timers.

    Dn bit from first timer enables 2nd timer.
    Dn bit from 2nd resets 1st.

    Pulse from timer1 dn bit will be on for T2 then off for T1.
     
  7. inwo

    Well-Known Member

    Nov 7, 2013
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    Your counter suggestion should work.

    I would use a separate counter and rung for each command.

    Latch a rung true to a counter with series dn bit from "pulse" timer.
    When count is reached, unlatch rung.

    Another rung for the output would use the pulse timer output made true by C1 or C2 or C3

    I'm sure it needs more housekeeping, but without drawing it out, it will just get confusing.
    ie. You may need interlocks to prevent two pulse streams at the same time.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The full picture is not really been posted, is the pulse number pre-selected in the ladder and then the series of pulses is output on a single output, if so at what rate and duration is needed.
    A series of pulses from either a single output or more than one should not be that hard, but more details are needed as above.
    Max.
     
  9. aaron12345

    Thread Starter New Member

    Dec 11, 2013
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    Thanks everyone. I will see what I can come up with from the advice. I will try to post a pic of the information shortly. Once again, thanks for everyone's help and advice.
    -Aaron
     
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    We'll assume that the camera needs a given pulse width, & pulse repitition rate, PRR which can be provided by a 555. Some one or thing must know how many pulses are required, which inf can be stored in a counter, or shift register. Using an up-down counter, multi input NOR, 555, & a control flip-flop might work. The up count can be manually loaded, hitting the start button sets FF, which enables reset on 555, outputting a 250 ms pulse, trailing edge advances counter downward. When counter reaches 0 count, NOR output goes hi resetting FF.??
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    This is being operated with a commercial PLC. ;)
    Max.
     
  12. aaron12345

    Thread Starter New Member

    Dec 11, 2013
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    0
    All,

    So, I think I have come up with a way to control the pulses with one shot coils controlled by two different timers. I appreciate everyones advice. I'm sure there is a better way of doing it, but this is the best that i can come up with. Not to mention, I am mostly familiar with AB PLCs, not DL. I will let everyone know how it works tomorrow after we program the camera. Once again, thanks.
     
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