A PLC (Programmable Logic Controller) consists of several hardware components, each with its own function. Here are the main hardware components of a typical PLC and their functions:
Processor (CPU):
The processor is the brain of the PLC and is responsible for executing the program instructions stored in the memory.
The fundamental hardware of a Rockwell Automation PLC (Programmable Logic Controller) is the processor, often known as the CPU (Central Processor Unit). Which is in charge of carrying out the stored program instructions in the memory. It executes arithmetic and logic operations to carry out program instructions, much like the CPU in a computer.
An Arithmetic Logic Unit (ALU), which executes arithmetic and logic operations, and a Control Unit (CU), which controls the flow of data between the processor and the memory, are two of the components that make up the processor. Moreover, the CPU features registers that serve as temporary data or instruction storage during processing.
The fetch-decode-execute cycle is the method by which the processor carries out program instructions. The CPU pulls the subsequent instruction from memory during the fetch stage. The processor decodes the instruction and decides what action to take in the following phase. The processor carries out the operation and stores the outcome in the execute phase.
Input module:
The input module receives signals from sensors or other input devices and converts them into digital signals that the PLC can understand.
A PLC’s input module is a piece of hardware that collects signals from sensors or other input devices and transforms them into digital signals the PLC can comprehend. By reading the state of input devices and sending that information to the PLC’s CPU for processing, the input module is in charge of interacting with the physical environment.
Many signal types, including analog, digital, and special-purpose signals, can be received by input modules. The input module transforms continuous, time-varying analog data, such temperature or pressure, into a digital signal that the processor can understand. Digital signals, which the input module directly reads, are binary signals with only two possible states: on or off. Specific input modules must be used to interact with the PLC in order to interface with special-purpose signals, which are unique to particular types of sensors or devices.
Depending on the application, input modules are often made to handle a single type of signal or a variety of signals. To provide precise and dependable signal delivery, they could also offer supplementary capabilities like signal conditioning.
Output module:
The output module sends signals to control devices, such as motors or valves, based on the program instructions executed by the CPU.
An Allen Bradley PLC’s output module is a piece of hardware that, in accordance with the program instructions carried out by the PLC’s CPU, transmits signals to control devices like motors or valves. By controlling the status of output devices based on the output signals produced by the PLC’s software, the output module is in charge of interacting with the physical world.
Several output signal types, including digital, analog, and special-purpose signals, can provide via output modules. Digital signals, which can only have one of two states—on or off—are binary signals that are use to operate relays, solenoids, or lighting fixtures. Analog signals are utilize to control devices like motors or valves that need a variable input because they are continuous signals that change over time. Special output modules must be interfaced with the PLC in order to handle special-purpose signals, which are unique to specific device types.
Output modules are typically design to handle a specific type of signal or a range of signals, depending on the application. They may also provide additional functionality, such as signal conditioning, to ensure accurate and reliable signal transmission.
Power supply:
The power supply provides the necessary voltage and current to power the PLC and its components.
A PLC power supply is a device that gives a programmable logic controller (PLC) and all of its related modules and components the required electrical power. A regulated DC voltage that is appropriate for powering the PLC is created by the power supply using the input voltage from the AC mains or a DC source.
A PLC power supply’s primary job is to give the PLC and its many modules, including input/output (I/O), communication, and programming devices, a steady and dependable source of power. The power supply generally has a broad input voltage range and is capable of accepting many input voltages, including 24VDC, 48VDC, 220VAC, and 110VAC.
Depending on the exact application needs and the type of PLC system being used, PLC power supplies come in a variety of form factors. Power supplies that are install on a DIN rail, a panel, or a chassis are some examples of popular power supply designs.
The power needs of the PLC system, the input voltage and frequency, the efficiency and dependability of the power supply, the available space, and the mounting choices should all be taken into account when choosing a PLC power supply. In order to guarantee the appropriate operation and lifetime of the PLC system, a dependable and efficient power supply is essential.
Memory:
The memory stores the program instructions, data, and variables used by the PLC. There are typically two types of memory in a PLC: ROM (Read-Only Memory), which stores the firmware and other permanent data, and RAM (Random-Access Memory), which stores the program and data during operation.
The program instructions for the PLC are permanently store in the program memory, sometimes refer to as the read-only memory (ROM). Since the program memory is non-volatile, the store information is keet even when the power is turn off. The user-define program instructions that regulate the PLC’s operation are store in the program memory, together with the operating system for the PLC.
The PLC stores temporary data, such as input/output status, timers, counters, and other variables required for the program execution, in the data memory, also referred to as the random-access memory (RAM). The store data is loss when the power is switch off since the data memory is volatile. To avoid data loss in the event of a power outage, a backup power source, such as a battery or capacitor, is used to power the data memory.
Communication module:
The communication module allows 1766-L32AWA MicroLogix 1400 PLC to communicate with other devices or systems, such as sensors, other PLCs, or a SCADA system.
A programmable logic controller (PLC) can be expanded to include a PLC communication module to enable communication with other systems or devices. The PLC may exchange data with other devices or systems across a variety of communication networks, including Ethernet, serial, and fieldbus networks, thanks to the communication module’s provision of the required hardware and software interfaces.
A PLC communication module’s primary job is to make it easier for data to be sent between the PLC and other hardware, including human-machine interfaces (HMIs), supervisory control and data acquisition (SCADA) systems, remote input/output (I/O) devices, sensors, and actuators. As a result, the PLC may collect information from the linked devices, keep track of their state, and manage their operation in accordance with the preprogrammed logic.
Depending on the network architecture, the require speed and bandwidth, the number of connect devices, and the communication protocol being use, PLC communication modules are available in a variety of types and combinations. Ethernet/IP, Modbus TCP, Profibus DP, DeviceNet, CANopen, and AS-i are a few examples of typical communication module types.
A PLC (Programmable Logic Controller) communication’s module is a piece of hardware that allows the PLC to connect with other devices, including computers.