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.
Questions tagged [plc]
1091 questions
7
votes
3 answers
Why Elsif not Else If In PLC programming
Im a PLC programmer and I am wondering why the reserved word elsif (ie without the E ) is used. I know that elseif or any other combination is not used as reserved words. Is there a history to use this in other Languages. If so why? just to save…
mrebus
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7
votes
2 answers
C set a bit (bit manipulation)
I'm programming a industrial plc and I have to manipulate bits for a profi-bus communication with a VFD. I get a 2byte status and have to send 2byte commands. For this operations I have to set bits to get the VFD operating. For example:
…
Gerald Zehetner
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7
votes
12 answers
PLC Programing in C# .NET
Can I Write Programs for PLC Controlling in C#?
How?
Hossein Moradinia
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6
votes
3 answers
Any successful profibus communications from .NET?
Has anyone successfully talked profibus from a .NET application?
If you did, what device/card did you use to accomplish this, what was the application, and did you use any kind of preexisting or available code?
GEOCHET
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6
votes
1 answer
Reading a JSON structure from a web server page on a Siemens S7 1500 PLC
I've been working with HTML and javascript to create graphical web pages to display data from my Siemens S7 1500 PLC. I've been using a $.getJSON command to successfully read values from the PLC when the web page that requests the information is…
Ryan Y
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6
votes
1 answer
Sending a boolean value to a PLC from Android
I was able to make a connection with a PLC to read data from it. Now there's one problem and it is that I have to write a method to modify the data from the PLC. To achieve this, I have to send two values to the PLC: an int value and a boolean…
Marialvy Martínez
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5
votes
5 answers
Where is a good place to start with making an application in .NET that communicates through OPC?
Where is a good place to start with making an application in .NET that communicates through OPC?
GEOCHET
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5
votes
1 answer
Read/Write S7-1200 bit memory via C#
I am trying to set value on a boolean memory in the S7-1200 CPU, I have used the SNAP7 library but I couldn't get success with it :
Result result = new Result();
byte[] Buffer = new byte[26];
Client.DBRead(1, 0, 2, Buffer);
result.bArret =…
Erwin Draconis
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5
votes
1 answer
How to declare local variable (Allen Bradley studio 5000)
How to declare local variable in structured Text in Allen Bradley studio 5000.
I have tried the following which did not work. mnemonic/syntax is not recognized?
VAR
x: INT;
END_VAR
global variables do work as, TEST_INPUT and TEST_INPUT_BOOL …
user6235593
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5
votes
2 answers
HTTPS Client for Siemens S7
I've a RESTful HTTP API. Now I would like to send HTTPS requests from my S7 PLC to the API. I've contacted Siemens and they said that they don't have a HTTPS client implementation.
But there is a tcpClient module in the library. And since TCP is the…
Tobias
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5
votes
4 answers
A Question About PLC Instructions
Can an input X1 change while instruction sequence is still being processed?
e.g.
LD X1
AND X2
OUT Y1
LD X1 // Can X1 loaded here differ from the previous one?
AND X3
OUT Y1
Thanks
Betamoo
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5
votes
2 answers
Pymodbus Read/Write Floats (REAL)
I have modbus mapping setup in my AB Micro820 PLC. I have an array in 40001 for writing, and one in 42001 for reading. Both are 200 elements and REAL type (32-bit float). I can write and read currently, so I know the code works, just incorrectly.…
xinthose
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5
votes
6 answers
Timers in PLC - Structured Text
How do timers work in PLC Structured Text (ST)? How do we declare them?
I've been studying a standard of PLC (IEC 61131-3), and they do not speak about timers in ST. I know the great majority of PLC programmers do them in ladder logic, but in this…
Yoanribeiro
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5
votes
5 answers
PLC Structured text, convert decimal to real(float). Not getting the value I expect. (IEEE-754)
I have a hardware that is communicating with the PLC over Profibus DP, that sends
me 4 bytes of data in hex that is "44 79 FF FF" and in the PLC program I have declared
a BYTE array for this input data. The problem is in the PLC the data I receive…
hijack
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5
votes
6 answers
Best IDE for PLC ladder programming
Recently I trying to learn Ladder Logic programming for PLCs, but I want to know if there is any IDE to create Ladder programs better that Step7 or cx-programmer? Is there any plugin for Visual Studio or Netbeans that I can use? Finally, is it…
Ali Foroughi
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