Is there a systematic way to get solution in PLC programming?

Discussion in 'Homework Help' started by anhnha, Dec 17, 2013.

  1. anhnha

    Thread Starter Well-Known Member

    Apr 19, 2012
    I am struggling with ladder diagram for traffic light. Is there a systematic way to get the solution?
    I don't know if Karnaugh map works here. I have searched a lot but there is not a complete guide on this.
  2. odinhg

    Active Member

    Jul 22, 2009
    Are you familiar with the finite-state machine? It might help you get it done.
  3. anhnha

    Thread Starter Well-Known Member

    Apr 19, 2012
    Yes, not good but I have used it many times. I have seen flow charts used in some books.
    Did that what you mean?
    By the way, can I use karnaugh map here?
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    When one can end up with hundreds of rungs on a ladder diagram it would become difficult to envisage how a Karnaugh map would assist in the design. Add the complexity of timers, counters, computational blocks and HMI's and you have a grander design to accomplish. The matter of knowing the required system state at the completion of each execution cycle is a key factor as is the verification & testing of those states.
    Experience is therefore important and also studying how other designers do this work is helpful. PLC manufacturers may offer training courses.
    Last edited: Dec 18, 2013
  5. Jony130

    AAC Fanatic!

    Feb 17, 2009
    I also use PLC in my job and I never see any PLC programmer witch use karnaugh map.
    All you need is experience and split the "problem" into small pieces.
  6. anhnha

    Thread Starter Well-Known Member

    Apr 19, 2012
    Thanks everyone.
    I thought that there is a systematic way to solve most of problems. I saw my professor struggling for a while to complete a ladder for traffic light. That made me wonder how can I do it well as even my prof also had to go through it four or five times before got it right.
  7. MaxHeadRoom


    Jul 18, 2013
    One often recommended way to start is the flow chart method.
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
    one way to symplify the trafic control light timer is to use the master clock. a simple store and compare to control whitch light is on. much easier than using a bunch of timers. just run a counter off the 1 second clock, then compare the count with presets to determine the output to turn on.