INTRODUCTION TO PLC - TUTORIAL 1

Architecture of PLC

How does PLC work?

• PLC collects data from sensors or input devices which is located infield area, process the data according to programming and trigger the output.

• According to the input and output, PLC can monitor and record scan time data such as machine productivity or operating temperature, start and stop process, generates alarms and more according to the programming. 

Key features

1) Input/output module: 

• PLC input and output module connect the PLC to the rest of the machine. i/o module can be either analog or digital.

• The input device might be a sensor, switch, and meter output device might include relays, light, valves, and drives.  Users can mix and match a plc,s i/o in order

• User can mix and match a PLC’s  I/O in order to get the right configuration for their application

2) Communication:

• PLC communicates with multiple devices. In addition to input and output devices, PLC connects with directly or indirectly. For example, users might want to export application data recoded by the PLC to a supervisory control and data acquisition system, which monitors multiple connected devices.

3) HMI (Human-machine interface )

• To interact with the PLC in real-time, users need an HMI. HMI is a kind of display that shows the real-time measuring variable, users can read and write through the keyboard or large touchscreen panels. Users can add input and also read output from display.    

How is PLC programmed?

• A particular PLC has their particular software to written program

• A PLC program is usually written on a computer and then download to the controller

• Most of PLC programming software offers programming in ladder logic or “C“

• Ladder logic is newly programming language for PLC

• Ladder logic represent through circuit diagrams with Rung

• Each rung represent specific logic and specific action by the controller in PLC

• Generally Ladder logic write from Left to Right

• As per the requirement, logic can be created and implemented by PLC

• PLC ladder logic programming example as given below 

Advanced PLC Features

• Nowadays the internet of things(IoT) is an industrial platform to connect with PLC. Industry 4.0 programmable controller are called upon to communicate data via a web browser, connect to databases via SQL, and even to the cloud data via MQTT