PLC stands for “Programmable Logic Controller”. A PLC is a computer specially designed to operate reliably under harsh industrial environments such as extreme temperatures, wet, dry, and/or dusty conditions. It is used to automate industrial processes such as a manufacturing plant’s assembly line, an ore processing plant, or a wastewater treatment plant.

PLCs share many features of the personal computer you have at home. They both have a power supply, a CPU (Central Processing Unit), inputs and outputs (I/O), memory, and operating software (although it’s a different operating software). The biggest differences are that a PLC can perform discrete and continuous functions that a PC cannot do, and a PLC is much better suited to rough industrial environments. A PLC can be thought of as a ‘ruggedized’ digital computer that manages the electromechanical processes of an industrial environment.

PLCs play a crucial role in the field of automation, using forming part of a larger SCADA system. A PLC can be programmed according to the operational requirement of the process. In the manufacturing industry, there will be a need for reprogramming due to the change in the nature of production.

Here I use Siemens PLC IDEs like Tia portal and Logo Comfort.

1) Bus Doors Ladder Program in Logo Comfort

Bus door’s Ladder Program in Logo comfort for Siemens miniPLC called LOGO.

By pressing start button, door 1 will be opened and pressing again for door 2 opening and stop/start to close both.

Download .lls file and simulate it in Comfort :

2) Industrial Mixer in Tia portal

We have two tanks (two materials flow), mixer, blower, 3 valves and etc. that are shown in below picture. I’d uploaded simulation video on YouTube that you could use my program from below video.

Industrial Mixer GUI in HMI

We need Control Philosophy with explained P&ID sketches to get appropriate program for production lines/processes. This requirements document has different names in various industries. Under good automated manufacturing practice (GAMP), common in the FDA regulated industries, it is called user requirement specification (URS). In batch industries it is called basic process operations (BPO), and in continuous plants it is usually called conceptual functional specifications (CFS) or simply functional specifications (FS).

A BPO document is a first step in creating a control system for controlling the (production) process. The BPO document is a generic document independent of the platform upon which it will be implemented. The BPO document should be written with enough details so a (process) control engineer / programmer would be able to use it to write a detailed functional specification (DFS) document. The DFS is a translation of the BPO document into a specific type/product of control system. Reading the DFS enables the control engineer/programmer to write/build the control software/application for controlling process operation.

The BPO document should contain the following chapters:

1. The unit
1.1. P&ID / process sketch
1.2. List of main/relevant equipment and all instruments
2. The process
2.1. General process description (in words)
2.2. Process parameters
2.3. General interlocks and alarms
3. The operation
3.1. Preliminary conditions
3.2. Detailed process description
3.3. Hold execution
3.4. Abort execution

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