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PLC programming

  1. Jul 26, 2015 #1
    Hi everyone,
    I have opted for an instrumentation course and I am worried about the programming part as i dont have much knowledge about programming. Is it necessary to learn C before learning PLC programming or i could start from plc programming? If I could start from plc then which book i should follow as a beginner?

    Thanks in Advance
  2. jcsd
  3. Jul 27, 2015 #2


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    C is a standard programming language, but there is no standard "PLC programming language". Every PLC manufacturer has his own PLC programming language and programming methods. Included in some PLC program is for example:

    - Logical control which could be programmed by use of ladder network or sequential network.
    - Dynamic control of motors ( e.g. PID controllers ).
    - Human/machine interface ( HMI ).
    - Local area network ( LAN ).

    Generally it's a good idea to be familiar with Karnaugh maps ( reduction of logical expressions ) and PID control, but as said above, the method as how to implement the requirements, strongly depends on the PLC used.
    Last edited: Jul 27, 2015
  4. Jul 27, 2015 #3


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  5. Jul 27, 2015 #4
    Relay Ladder Logic programing languages came in to being because it tried to emulate what electricians were wiring up every day. In essence, they were attempting to take electricians and make them in to programmers. That sort of thinking didn't always work well. They often wrote awful RLL software. However, the opposing point of view, that software programmers could write reasonable programs around an industrial process is also deeply flawed for the opposite reason.

    Ultimately, to learn RLL well, you need to become intimately familiar with a process, and all the quirks of the I/O. For example, if a valve actuator is moved from, say 10% to 60% open, it may overshoot and need to work backwards a bit. This could confuse a poorly written program that just assumes that the actuator will always hit the target perfectly.

    Your professor won't know a damned thing about these sorts of problems UNLESS they have at least a couple years of hard-hat field experience. If they have that, then pay attention! If they don't, or they consult here and there, you might as well focus on just passing the tests.
  6. Jul 27, 2015 #5
    Thanks alot Hesch!

    As i have done Degree in Electronics and have good knowledge about karnaugh maps and I will be studing about PID. Thanks for the link will look forward to join that.

  7. Jul 27, 2015 #6
    Thanks Sir! I appreciate your valuable advise.
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