PLC

Discussion in 'Programmer's Corner' started by Ahlawygamd, Apr 14, 2006.

  1. Ahlawygamd

    Thread Starter New Member

    Apr 14, 2006
    2
    0
    I'm Egyptian
    I will participate in Robocon Egypt 2006 next July

    I want to learn programming of PLC and how can I use PLC
    Can you help me
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    I would start by learning how to write and understand ladder logic. I think you can google this term. Many PLC's are still programmed according the this methodology because plant electricians (at least in the US) are familiar and comfortable with this method.

    The next step would be contact PLC vendors or go to their websites. Here you are looking for demo software that will allow you to program one of their products. I don't know if the following companies have a presence in Egypt, but you should be able to establish that with minimal effort.

    Major PLC Vendors

    Allen-Bradley
    Omron
    Siemmens
    Eaton/Cutler-Hammer
    Square-D
     
  3. Ahlawygamd

    Thread Starter New Member

    Apr 14, 2006
    2
    0
    Dear Papabravo
    Thank you , your help is very useful for me

    I think that Siemens has a branch in Cairo , I will contact them

    but i have a problem on treating the hardware of the PLC
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    Each PLC is different but the basic idea is to treat each "rung" of a ladder as a single boolean equation. In a real ladder logic implementation with relays all the equations are "solved" in parallel in continuous time. In a PLC the processing algoithm is executed repeatedly at high speed.

    The Basic PLC Algorithm
    Code ( (Unknown Language)):
    1.  
    2. DO
    3.  1. Sample and gather the inputs into an "input image table"
    4.  2. Solve each of the ladder rungs to create an "output image table"
    5.  3. Update the real outputs from the "output image table"
    6. WHILE(1)
    7.  
    8.  
    The basic hardware device in ladder logic is the relay. What are the properties of a relay? Well it has a coil, like the one in a solenoid. The coil is energized if it has current flowing through it. The current can be either AC or DC. If there is no current flowing in the coil it is de-energized. A relay will have one or more contacts associated with it's coil. These contacts are called NO(Normally Open) and NC(Normally Closed). These terms describe the state of the contacts when the coil is de-energized. When the coil is energized an NO contact will close, and an NC contact will open.

    To implement a boolean function with contacts and mechanical switches you connect them in series to perform an "AND" function and you connect them in parallel to perform an "OR" function.

    In the PLC there is often a graphical interface that will allow you to write your control progam in terms of "relay ladder logic"

    Hope this helps.
     
  5. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Many PLC manufacturers also offer free programming software with instructions, demo's and built in simulation (the Zelio series I have used certainly do).
    Others may offer a Starter pack with PLC/Software/demo's/Programming cable/and comprehensive instructions.
    Wont hurt to ask
     
  6. bhavesh96el

    Member

    Apr 24, 2006
    11
    0


    Try this website http://www.plcs.net/

    it is good
     
  7. engs1982

    New Member

    Feb 7, 2009
    2
    0
    i am also learn the pl myself only, so u choose siemens logo plc it very easy, also the siemns web pronide the demo s/w i.e soft comfort

    try it , do it
     
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