Answer to Question #205350 in Electrical Engineering for Bahawal Tahir

Question

(a) what do you understand by programming logic controller?how do PLC work? illustrate with example. highlights various types,physical structure and applications? (b) draw and explain typical block diagram of PLC?

Answer 1

Part a

A ruggedized computer used for industrial automation is known as a Programmable Logic Controller or PLC. These controllers can automate a single operation, a machine function, or an entire manufacturing line.

The PLC collects data from linked sensors or input devices, processes it, and then activates outputs based on preset settings.

A PLC can monitor and record run-time data such as machine productivity or operating temperature, start and stop operations automatically, create alerts if a machine fails, and more, depending on the inputs and outputs. Programmable Logic Controllers (PLCs) are a versatile and reliable control solution used in practically any situation.

What is a programmable logic controller (PLC)?

PLCs differ from industrial PCs, microcontrollers, and other industrial control technologies in a few fundamental ways:

• Input and output modules (I/O) - The PLC's CPU stores and processes program data, but input and output modules (I/O) connect the PLC to the rest of the machine; these I/O modules send information to the CPU and trigger specified outcomes. Sensors, switches, and meters are examples of analogue input devices, whereas relays, lights, valves, and drives are digital output devices. Users can mix and match the I/O on a PLC to get the best configuration for their needs.

• Communications - A PLC may need to link with other systems in addition to input and output devices; for example, users may wish to transfer application data collected by the PLC to a supervisory control and data acquisition (SCADA) system, which monitors several linked devices. To guarantee that the PLC can connect with these other systems, PLCs include various ports and communication protocols.

• HMI - An HMI, or Human Machine Interface, is required to interface with the PLC in real-time. These operator interfaces might be modest displays with a text-readout and keyboard or enormous touchscreen screens that resemble consumer gadgets, but they always enamour the user.

Part b

The PLC system's heart is the central processing unit. The CPU replaces central relays, counters, timers, and sequencers with a microprocessor-based control system. A processor only occurs once and can be either a one-bit or a word processor in a PLC. When it comes to logic operations, one-bit processors are sufficient. When processing text and numerical data, calculating, measuring, regulating, and recording and the simple processing of signals in binary code, PLCs with word processors are utilized.

The operating concept of a CPU may be summarized as follows.

• The CPU takes (reads) data from a variety of sensors. runs the user application from memory and delivers the proper output directives to the control devices. • To provide the low-level voltage required by CPU and I/O modules, a direct current (DC) power supply is necessary. Depending on the PLC system manufacturer, this power supply might be integrated into the CPU unit or be a separate device. The CPU has various electrical components and ports for connecting cables to other devices and operational key switches.

Input/output modules connect input devices (such as start and stop buttons, sensors, restricted switches, and selector switches) to the microprocessor. Also used to connect output devices (such as electrical heaters, lights, solenoid valves, relays, buzzers, and fans) to the CPU. The input module transfers information to the processor, while the output module transforms information from the processor to the load.

The input/output module is responsible for ensuring that input devices and processes are kept separate. Also, to provide separation between the processor and the output devices. Use the optocoupler for isolation modules.

Push buttons, limited switches, sensors, and selection switches are all hard-wired terminals on the input modules. The output modules are hardwired with output devices such as tiny motors, motor starters, solenoid valves, and indicator lights.

The output module connects the output load to the processor; it performs the same job as the input modules but in reverse order. The block and circuit diagram of the output module is depicted in the diagram. It is divided into two portions, the first of which is the logic section and the second of which is the power portion.