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Questions tagged [plc]

PLC (Programmable logic controller) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures.

1091 questions
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Hangs on Socket.Receive with no exception

I have WPF C# application that communicate with a PLC (i.e. write/read Omron PLC's memory addresses) through Ethernet (UDP packets) using FINS command/frame. I can send command to WRITE PLC address successfully, but application hangs/crashes when…
KMC
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What language is behind ladder programming in Omron PLC?

What does the ladder programming in PLC convert to? Does the graphic command (e.g. open contact, instruction etc.) a BASIC or C instruction, or does it compile to assembly language directly?
KMC
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C to IEC 61131-3 IL compiler

I have a requirement for porting some existing C code to a IEC 61131-3 compliant PLC. I have some options of splitting the code into discrete function blocks and weaving those blocks into a standard solution (Ladder, FB, Structured Text etc). But…
Peter M
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How can I use a local TwinCat 3 runtime with Hyper-V enabled?

I'm trying to run TwinCat 3 XAR in a PC where I need to have hyper-V ON to run Azure IoT Edge (which uses hyper-V). Is there a way to run XAR with hyper-V turned on? Is there any way to isolate the cores from hyper-v or something else?
Paulo Ilheu
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What is the benefit of defining enumerators as a DUT?

The main goal of defining enumerators is to assign a variable to some numbers and their equal strings as I understand. We can define var a as an enum everywhere in the initializing section of our Program or Function Block like…
asys
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Resources to accessing a S7 Profinet PLC (1212C) from Java

I have a relatively special question here. At least I think it's special as Google didn't seem to be able to provide me with the information I was looking for. I have recently purchased a S7 Starter Kit, containing a S7 1212C PLC. It's all setup and…
Christofer Dutz
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How to assign an initialized array to an array of arrays in TwinCAT

I'm trying to assign two initialized arrays evenNumbers and oddNumbers to an array of arrays integers: PROGRAM ArrayInit VAR evenNumbers : ARRAY[1..3] OF INT := [2, 4, 6]; oddNumbers: ARRAY[1..3] OF INT := [1, 3, 5]; integers :…
Roald
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Twincat3: Can't connect to LabVIEW's Modbus TCP/IP server via Tc2_ModbusSrv library (on virtual PLC)

I am trying to create a simple Hello World Modbus TCP/IP program using Twincat3 and virtual PLC (PLC running locally on my computer). I have set up a LabVIEW Modbus TCP/IP master + slave program (both of which are working see screenshots below). I…
Jakub Szlaur
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Interfacing .NET with Siemens PLC S7 200

I'm trying to interface .NET (C# or VB doesn't matter) with a Siemens PLC S7 200. I can't however get a connection set up. I'm working on a Win7 64bit machine but can't seem to get it working on 32bit either. I got two…
Henrik
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TwinCAT - How to measure program execution time?

I would like to measure the execution time of a structured text (ST) program. The task associated with the program is running at 10 ms. How do I measure execution time?
Piper
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How do I run a Twincat program without PLC?

I am a beginner in Twincat and have been playing around with it. I watched this playlist where this guy explain structured text and successfully runs a program on his system. However when I try to run on my system, I get error 0x1028. Then I read…
Piper
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Read a Siemens PLC s7 String in C# with S7netplus

I have trouble to read data in DB of a Siemens PLC S7 1500 using S7netplus. The situation: I have a C# application running. I connect on the PLC very well. I can read data such as Boolean, UInt, UShot, Bytes But I don't know how to read String…
Seb
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Unsolvable error with multiple requested values send to the plc (apache.plc4x)

I'm new here and my first question is regarding the request of PLC values, using Apache PLC4x. I want to loop through all the actual I, Q and DB available in the PLC. Because I want not able to accomplish this I looped through a set of DB but if the…
Titus
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Are CIP services for reading and writing PLC tags (on AB Logix 5000 controllers) atomic?

I'm following the Allen-Bradley documentation for controller data access using CIP, specifically the read tag service, write tag service, and details around reading/writing whole UDTs:…
Camputer
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What's the difference between plc's scan cycle and code surrended by while(1){ ... }?

I'm confusing that whether the plc's cyclic execution can be seen as a program surrounded by the endless loop. If not, what's the difference between them?
Eric
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