Plc ladder diagram for analog signal

Discussion in 'The Projects Forum' started by irfan16, Dec 29, 2011.

  1. irfan16

    Thread Starter New Member

    Dec 29, 2011
    12
    0
    Dear All

    Can any one guide me about the develpoing PLC Ladder diagram for analog input signal..

    My input signal to PLC is 0~24V
    I want to activate green led at out put of PLC when input voltage to plc is 10 volt..and red led when input voltage is 24v..

    Please reply if anyone know about this..

    Kind Regards

    Urfee
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    Statistically speaking, the leds would never light up because the voltage will never be exactly 10 nor 24V. You need to specify some intervals, like green led is on when V>10V or 9.9V<V<10.1V.
    Then you need to set up some comparators to get logic signals out of the continuous variabels, then make the PLC logic.
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I do not recognise the 0-24V analog signal. are you sure that is correct? All PLCs I know of, standardize on 0-10V, 4-20mA, and rarely 0-60mA or 0-20mA. Never seen 0-24V. In any case, depending on what PLC you have & what software I can't walk you step by step unless I know what you are using. You should have a symbol library that contains analog comparator functions like >, <, \leq, \geq, \neq. do you have these symbols?
     
    irfan16 likes this.
  4. anotheruser1

    Member

    Dec 6, 2011
    30
    4
    Its doable, but I need to know what programming software you are using and the processor
     
  5. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
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    Look up your cards input impedance configured as 0-20ma, calculate the appropriate dropping resistor that gives full scale current, Scale for full range, and off you go. Some older PLCs require specific multiple port read/writes to read your conversion, but most now is a simple port read. A simple looping compare and output will have you up and running.
     
  6. irfan16

    Thread Starter New Member

    Dec 29, 2011
    12
    0
    Dear Sir

    My input signal is 4~20mA. Actually I want to outputs. one output when input is 7 to 9mA, Second ouput when input is 13 to 16mA. And third out put will enrgise when input is 18 to 20mA.CAN U GUIDE ME HOW I SHOULD DEVELOP LADDER LOGIC..IF U SEND ANY EXAMPLE OF WRITTEN PROGRAM IT WILL SURELY VERY HELPFUL.. I am using ABB PLC AC500, CODESYS V2.3
     
  7. irfan16

    Thread Starter New Member

    Dec 29, 2011
    12
    0
    My input signal is 4~20mA. Actually I want to outputs. one output when input is 7 to 9mA, Second ouput when input is 13 to 16mA. And third out put will enrgise when input is 18 to 20mA.CAN U GUIDE ME HOW I SHOULD DEVELOP LADDER LOGIC..IF U SEND ANY EXAMPLE OF WRITTEN PROGRAM IT WILL SURELY VERY HELPFUL.. I am using ABB PLC AC500, CODESYS V2.3 [​IMG]
     
  8. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I dont have access to your codesys software, but heres how it would look like in RSLogix500. Pay attention to the "source B" numbers, you will need those.
    [​IMG]
     
    Last edited: Jan 5, 2012
  9. ersadheesh

    New Member

    Jul 20, 2012
    1
    0
    Dear Sir,
    I am using omron PLC, analog input 4-20mA getting as an Input. then I has to be multiple with 625(constant), then divided by 2.5, that value has to be added in every second till set value after reach set value one digital output will have to come. Please give one example ladder Diagram. I am using cx-one software omron. please help me to solve this problem.
    QUOTE=strantor;440337]I dont have access to your codesys software, but heres how it would look like in RSLogix500. Pay attention to the "source B" numbers, you will need those.
    [​IMG][/QUOTE]
     
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