Requirement Analysis

1.  Determine the Machine Sequence of Operation

Firstly, you have to decide what equipment or system you want to control. The ultimate purpose of the programmable controller is to control an external system. This system to be controlled can be machine equipment or a process and is often generically called a control system.

The movement of the controlled system is constantly monitored by the input devices and depending on a specified condition, sends a signal to the programmable controller. In response, the programmable controller outputs a signal to the external output devices, which controls the movement of the controlled system and thus achieves the required control action. In simplicity, you need to determine the sequence of the operation by drawing out the flowchart.

2.  Assignment of Inputs and Outputs

Secondly, all external input and output devices to be connected to the programmable controllers must be determined. The input devices are the various switches, sensors etc. The output devices are the solenoids, electromagnetic valves, motor, inductors etc.

After identifying all the various the particular programmable controller you will be using. The actual wiring will follow the numbers of the programmable controller. The assignment of INPUT and OUTPUT numbers must be carried out before writing the ladder diagram because the number dictate what is precise meaning of the contacts i9n the ladder diagram.

3.  Writing of the Program

Next, write the ladder diagram program by following the control system sequence of operation as determined by step one.

4.  Programming into Memory

Now, you can apply power to the programmable controller. Depending on the type of programmable controller, you may have to do an I/O generation to prepare the system configuration. After that, you can enter your program in the memory either by programming console or by computer aided ladder software tool. After completion of the programming, you should check for any coding errors by means of diagnostic function, and if possible simulate the whole operation to see that everything is working accordingly.

5.  Running the System

Before the start pushbutton is pressed, thoroughly ensure that the input and output wiring are correctly connected according to the I/O assignment. Once confirmed, the actual operation of the PLC can now be started. You may need to debug along the way and fine tune the control system if necessary. Test run thoroughly until it is safe to operate by anyone.

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