PLC Programming-4

By IKTech May 29, 2017

PLC Instruction Type

To write a program for a PLC, it is essential to get familiar with various instructions for setting up PLC instructions. A brief image is provided here, more details will be found in following PLC studies. Note here that according to the type of PLC the instructions are different. From the beginning, this curriculum is going on in accordance with the Mitsubishi FX series.

At the end of today’s text, you can find out what:

3 different types of instructions.

√ The most common basic instruction names.

√ Know the instructions and how they are done.

Basic Program Instructions

This category refers to the devices that are related to 4 basic bit devices (X, Y, M, and S), timer devices, counter devices and operations. There are also more sets, reset and pulse functions. It is possible to complete 80 ~ 90 percent of a program by these instructions.

Ladder Setup Instructions

Ladder setup instructions are used in step ladder programming (STL). This programming is similar to the SFC programming, which can be seen in the form of a flow chart. But the flow chart will remain in place and the code will actually be composed by Ladder Logie. When programming logger logic, the STL contact is a common instruction that will check whether a state is active. S relays are used to state statewide.

STL programming is not usually included in this class. However, excellent explanations and examples can be found in the FX3U programming manual.

Applied Instructions

These guidelines are the ‘efficient’ instructions for the FX line. These instructions will allow you to relate complex PLC complicated information, mathematical operations, and communications. Most instructions are applied to 16 bit or 32bit word levels.

………………………………………….. ………………………………………….. …..

Since the basic instruction can write 80 ~ 90 percent of the program, so its use is also very much.

Basic Instructions

Basic instructions are the bit control instructions. Generally they constitute up to 90% of the laser program. Manipulat output, bit shift and master control knitting contact are used to ensure input status of them.


Previously I gave some ideas about this. Now give the details.

Normal Open Contact: This mark will be attached when the device gets power. In the instruction mode, the memorial is LD, which is the load for the LOAD. This sign occupies 1 step program place.

Normal close contact: This sign will be attached when the device does not get power. In the instruction mode, the membrane is LDI, which is the LOAD INVERSE. This sign occupies 1 step program place.

Coil control: This symbol is always displayed right before the vertical ladder rails. It will get power when it will be run before Logie. When the power is received, the address becomes active with the same output. OUT in the instruction mode OUT is memorable for ACTIVATE OUT. This symbol usually occupies 1 step program, unless it occupies 5-step space for timer and counter-instruction.

Bracket Control: This symbol is usually displayed before the vertical ladder rails on the right when the bit is controlled. These symbols are usually used for the word device command. But a few bit instructions can be used correctly with a bracket symbol. It will be powered by the power when it will be run before Logie. This symbol occupies multiple steps of the program based on the command used.

Invert: This sign returns all the previous logic. If the logic is true before the InvertPoint, the output of the invert is false. And if the logic is false, then the output of the invert is true.

It is very important to clear the above concepts before moving to the next step. These symbols are used primarily to reveal the device’s own non-active status. However, if approved through a power stream, it will display its status through the device.

For example, a lamp switch is closed (non-active state), no current flows (unless it is turned on). If you switch on this condition (active condition), the electric current will flow and the lamp will burn. This indicates that the light switch is the normal open contact.

Normally close contact is always the opposite. The current will continue to flow until the switch is activated. A common example is an e-stop (emergency stop). The current will be flowing until an operator has hit the emergency switches. If the switch hits, the switch will be disconnected and the power flow will be stopped.

Examples: Normal Open and Normal Close Contact

Notice the timing charts of the image. In Figure 1, the output is not active when the input is not active. In the second figure, if the input is not active, the output is active.

Today it is ………………………………….

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