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PC software to PLC input

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  • 20-03-2015 1:03am
    #1
    johnnyjb
    Registered Users Posts: 366 ✭✭


    Hi

    Hi im trying to get into the automation field and have been trying to query a few scenarios

    Could anyone explain how to connect a pc (running software for a box packing assembly line ) to the input of an Allen Bradley PLC.

    What would be needed to translate/convert the signal from the pc (when a task has been performed) to 24 volts etc. that a plc input would need to operate part of a conveyor (an electro pneumatic valve)

    Any help would be appreciated
    Thanks


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    #2
    DublinDilbert
    Registered Users Posts: 5,367 ✭✭✭DublinDilbert


    johnnyjb wrote: »
    Could anyone explain how to connect a pc (running software for a box packing assembly line ) to the input of an Allen Bradley PLC.

    More information is needed to answer your question.
    What software are you trying to connect? Who wrote it? Is it a SCADA package? Maybe a C# program that some person wrote in an afternoon?
    johnnyjb wrote: »
    What would be needed to translate/convert the signal from the pc (when a task has been performed) to 24 volts etc. that a plc input would need to operate part of a conveyor (an electro pneumatic valve)

    Any help would be appreciated
    Thanks

    Generally some form of serial link would be used:-
    RS232, RS485, Modbus, Ethernet, CAN to name just a few. It will depend on what interface is in your PLC and what interface your software was written to work with.



    The more correct way to connect a PLC to PC application these days is to use an OPC server and run it over Ethernet from both PC and PLC. But your system could of been designed 20 years ago and might not use anything like this.


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    #3
    johnnyjb
    Registered Users Posts: 366 ✭✭johnnyjb


    DublinDilbert wrote: »
    More information is needed to answer your question.
    What software are you trying to connect? Who wrote it? Is it a SCADA package? Maybe a C# program that some person wrote in an afternoon?



    Generally some form of serial link would be used:-
    RS232, RS485, Modbus, Ethernet, CAN to name just a few. It will depend on what interface is in your PLC and what interface your software was written to work with.



    The more correct way to connect a PLC to PC application these days is to use an OPC server and run it over Ethernet from both PC and PLC. But your system could of been designed 20 years ago and might not use anything like this.

    Thanks for your response

    There is a black cable coming from the pc (running software that releases a pneumatic blade when the correct Barcode has been scanned) to a junction box (which also has a power cable connected)

    The black cable then good on to an allen Bradley pico plc

    I do not know what is in the junction box and don't have any body to ask questions atm

    This is all curiosity on my behalf, trying to understand automation as i go


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    #4
    DublinDilbert
    Registered Users Posts: 5,367 ✭✭✭DublinDilbert


    johnnyjb wrote: »
    Thanks for your response

    There is a black cable coming from the pc (running software that releases a pneumatic blade when the correct Barcode has been scanned) to a junction box (which also has a power cable connected)

    The black cable then good on to an allen Bradley pico plc

    I do not know what is in the junction box and don't have any body to ask questions atm

    This is all curiosity on my behalf, trying to understand automation as i go

    What port is the black cable plugged into the PC?


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    #5
    dave2pvd
    Registered Users Posts: 1,511 ✭✭✭dave2pvd


    First off, the PLC is what controls the electro-pneumatic valve (aka solenoid valve).

    The PLC program is what runs the box packing assembly line. You need Allen-Bradley software to make any edits to the PLC's program. Look up their website (here) for more info.

    Sounds like you have a PC application running the bar code scanner, etc. This is communicating to the PLC, probably via a serial cable.

    If I was you, I'd go looking for a wiring diagram before going any further.


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