Save to MyST

Programmable Logic Controllers (PLC)

Overview
Documentation
Tools and Software
Solutions
Programmable Logic Controllers (PLCs) are the key application enabling factories to operate in an automated way. PLC is typically built up as a modular system consisting of several blocks, such as control unit (often called central processing unit, CPU) and multiple Input / Output or other function modules (expansion modules). Control unit communicates with the expansion modules over a dedicated and usually a customer-specific bus called backplane interface. Control unit operates in cycles and periodically exchanges data with the expansion modules. The data are processed in the control unit in-between each consecutive cycles. The input / output modules make an interface / connection to the factory process side and provide information about various physical variables detected by sensors on one side and enable to interact with the automation process through different actuators driving on the other side. Each needs to be integrated in the complete automation system and therefore provides connectivity functions to various fieldbuses or industrial ethernet.

Fieldbus and Industrial Ethernet

In factory automation, data connectivity is essential, especially now with the Industry 4.0 concept widening its scope. A number of standards are used to support specifically developed fieldbuses including the classic CAN (Modbus and CANopen), RS-485
View application

Human Machine Interface

To help us effectively control equipment as well as make decisions based on machine feedback, we use a Human Machine Interface (HMI) which can be a simple display directly assembled on a machine for factory automation or multi-touch display panels fo
View application

Input/Output Modules

Input/Output (I/O) modules collect data from input devices including proximity, pressure, temperature sensors and push buttons, and control actuators such as valves, relays and lamps (output devices).  These modules can either be added to a Programma
View application

IO-Link Modules

Paving the way to Industry 4.0, IO-Link communication networks (IEC 61131-9) can be used for bi-directional, point-to-point data connectivity down to the actuator and sensor level, enabling data pre-processing, sensor parameter tuning and advanced di
View application

PLC Control Unit

The PLC Control Unit in a Programmable Logic Controller (PLC) is the main building block which processes data coming from input devices and controls outputs. It can be integrated with I/O modules to provide the required functionalities. The PLC contr
View application

Processing performance, speed and integration

Processing performance, speed and integration

With increasing complexity and continuous evolution of automated production lines, also the automation system requirements are rising rapidly. More data need to be exchanged over the input / output and other function interfaces and CPU cycles are expected to be shorter. Moreover, the systems are supposed to be well synchronized and to operate in a deterministic way.

The data exchange as well as communication is done in real-time with reduced latencies and minimized jitter. This strengthens the requirements on processing performances as well as connectivity architectures and the way of implementation. The industrial factories are often a very harsh environments in terms of pollution such as dust, humidity, chemical but also electro-magnetic field, noise and other disturbances.

Applications must be extremely immune vs. such tough conditions and disturbances and provide reliable operation over their very long lifetimes. Long-term availability, safety and security are another challenge for PLC designs.

Our products and solutions

ST has an extensive offer of STM32, 32-bit microcontrollers and microprocessors and the essential accompanying devices like EEPROM, RTCs and Supervisors and dedicated products ensuring the systems security when connected to a cloud.

Input / output modules can benefit from our highly robust current limited terminations (CLT) significantly reducing power dissipation and intelligent power switches (IPS), enabling reliable driving of industrial loads, able to comply with safety regulations (SIL) and offering also embedded galvanic isolation for high immunity and the most compact designs. Signal conditioning in analog peripherals can be solved by new operation amplifiers, current sensing chips or comparators.

Different application blocks supply circuits can be developed using ST power management ICs. High level of protection tailored according to the exact requirements can be granted thanks to the Transient Voltage Suppressors (TVS) or other protection devices. An essential part of the system are communication interfaces, which enable integration to factory automation system. ST provides solutions for both – wired connectivity through various fieldbuses and wireless connectivity technologies.