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Sunday, April 18, 2010

Operate the PLC - part 2

4.2.3.5. Basic PLC Programming
Globally, the programming language used on the PLC there are two, namely LADDER DIAGRAM and MNEMONIC CODE or STL (Statement List). But now, PLC already can programmed in five programming language.

• mnemonic codes
At the time of editing the PLC program using the Programming Console, we can not do it by using the Ladder diagram. The reason is because the average Programming Console display his view a little, so the screen is not sufficient to edit the ladder diagram and just enough to edit using STL or mnemonic code. So this is where we need to learn STL or mnemonic code. But there is also a Programming Console is specifically designed to be able to directly edit the program using ladder diagrams.

• Ladder diagram
Ladder diagram is used when we create a PLC program using the computer. Ladder diagrams are easier to understand than the mnemonic code. This is because the Ladder diagrams almost similar shape with the wiring diagrams. Grooves can be seen directly, without having to understand the many codes such as program code in mnemonic code.

STL and Ladder diagram on each brand of PLC has a different symbol, although its basic principles are the same.

Figure 4.7. Tools for PLC programming

Before we get to the ladder circuit we must first know the logic circuit wire / hard wire because of the appearance of ladder diagram logic comes from the wire / hard wire. Before the industrial revolution in 1960-1970 automation wire used in logic circuits where there are many weaknesses including pengkabelannya are so complicated, because each terminal is connected. To answer the challenge, Experts develop the PLC that can reduce using of wiring until 80%, which basically is a wire ladder logic diagram that moved into the software. Later we no longer assemble in hardware but in software.

Here is a variety of logic circuit wire / hard wire:


Here are some examples of conversion of electrical circuit diagrams to ladder diagrams are provided with the address.

Fg4.9g. Other forms of electrical circuit diagrams

Fg4.9h. Ladder diagrams of electrical circuits on Fg4.9g


a. Omron PLC Basic Instructions
• LOAD (LD) and LOAD NOT (LD NOT)
a prefix contacts at the bus bar. If at the prefix of the bus bar is the NO(normaly open) contacts, then the instruction is LOAD or LD. For the NC(normaly closed) contacts, then the instruction is LOAD NOT or LD NOT. See Figure 10.

Figure 4.10. Ladder and mnemonic code for a LD and LD NOT instruction on Omron PLC

• AND and AND NOT
the instruction for series connection in the ladder. For
NO(normaly open) contacts, then the instruction is AND. For NC(normaly closed) contacts, then the instruction is AND NOT. See Figure 11.
Figure 4.11. Ladder and mnemonic code for an AND and AND NOT instruction on Omron PLC

• OR - OR NOT
The instruction for parallel connection in the ladder. For NO(normaly open) contacts, then the instruction is OR. For NC(normaly closed) contacts, then the instruction is OR NOT. See Figure 12.

Figure 4.12. Ladder and mnemonic code for an OR and OR NOT instruction on Omron PLC

• Combination of AND and OR
If in a programs contained serial and parallel relations in one set, then the ladder can be seen in Figure 13.

Figure 4.13. Ladder and mnemonic code for a combination AND & OR instruction on Omron PLC

• OUT-OUT NOT
the instruction for output or load, such as Relay, Contactor, Light, Buzzer, and others. If the output is NO(normaly open), then the instruction is OUT, but if the output is NC(normaly closed), then the instruction is OUT NOT. See Figure 14.
Figure 4.14. Ladder and mnemonic code for OUT & OUT NOT instruction on Omron PLC


• END
The instruction for the end of the program, if a program does not end with the END instruction code, the program will not be able to do (error). See Figure 15.
Figure 4.15. Ladder and mnemonic code for END instruction on Omron PLC

• AND LOAD
the union between a parallel connection which is connected into one, so if there are two parallel circuits are combined into one, then the instruction is AND LOAD. See Figure 16.
Figure 4.16. Ladder and mnemonic code for AND LD instruction on Omron PLC

• OR LOAD
the union between a series connection which is connected into one, so if there are two series circuits are combined into one, then the instruction is OR LOAD. See Figure 17.
Figure 4.17. Ladder and mnemonic code for OR LD instruction on Omron PLC

• Combining AND LD and OR LD
In a more complex case there is a combination of AND LD and OR LD are used together.
Figure 4.18. Ladder and mnemonic code in combination of AND LD and OR LD instruction


• Encoding of instruction for the multiple right side
If there is one or more instructions written on the right with the same execution condition, it must be encoded in a row following the last condition on the line instruction.

Figure 4.19. Ladder and mnemonic code for encoding of instruction for the multiple right side


• The instructions for the line of branching
If an instruction line must branched two or more, sometimes is necessary to use TR bits to keep the condition at the point of branching. TR area provides eight (8) bits, TR0 until the TR7, which can be used to temporarily store the execution condition at the branch point. TR-bit instruction is only used if we program the PLC with mnemonic codes.

Figure 4.20. Ladder and mnemonic code for the line of branching



b. Basic Instructions of Siemen PLC

• Series connection

Figure 4.21. Ladder and mnemonic code for series connection on Siemen PLC


• Parallel connection

Figure 4.22. Ladder and mnemonic code for parallel connection on Siemen PLC


• the union of parallel connection
Figure 4.23. Ladder and mnemonic code for the union of parallel connection on Siemen PLC


• the union of series connection
Figure 4.24. Ladder and mnemonic code for the union of series connection on Siemen PLC




b. Basic Instructions of LG PLC

• Prefix contact
Figure 4.25. Ladder and mnemonic code for prefix contact instruction on LG PLC


• Series connection

Figure 4.26. Ladder and mnemonic code for series connection instruction on LG PLC


• Parallel connection
Figure 4.27. Ladder and mnemonic code for parallel connection instruction on LG PLC


• the inverting instruction
NOT is the reverse order of conditions that should, from the whole process a sequence of courses. See Figure 28.
Figure 4.28. Ladder and mnemonic code for NOT instruction on LG PLC


• the union of series connection
Figure 4.29. Ladder and mnemonic code for the union of series connection on LG PLC



• the union of parallel connection
Figure 4.30. Ladder and mnemonic code for the union of parallel connection on LG PLC