The “Brain” of Industrial Automation
A PLC, or Programmable Logic Controller, is an industrial controller designed to control machines and automated processes.
It receives signals from buttons, sensors, encoders, and other devices, then follows a programmed logic to control motors, valves, cylinders, conveyors, and other equipment.
I. Why Is a PLC Important?
In factories, many machines are not operated manually one by one. Instead, they are controlled automatically by PLC systems.
For example, when a product reaches a certain position on a conveyor, a sensor sends a signal to the PLC. The PLC can then stop the motor, activate a cylinder, or start the next process.
That is why a PLC is often called the brain of automation. It makes decisions, sends commands, and coordinates machine actions.
II. Why Was the PLC Created?
Before PLCs were widely used, factories mainly relied on relay control systems. These systems required a lot of wiring. When the production process changed, engineers often had to rewire the whole control system.
The PLC was created to solve this problem.
With a PLC, many control changes can be made by modifying the program instead of changing the wiring. This greatly improves efficiency and reduces maintenance costs.
III. What Are the Main Parts of a PLC?
1.Hardware
The hardware usually includes a CPU, power supply, input modules, output modules, and communication interfaces.
The CPU is the core of the PLC. It runs the program and processes signals.
Input modules receive signals from external devices, such as sensors, buttons, and encoder position data.
Output modules control external devices, such as motors, relays, valves, and alarm lights.
2.Software
The software of a PLC mainly refers to the control program. Engineers write the program according to the machine’s working logic.
For example:
When the start button is pressed, the motor starts.
When the sensor detects a product, the conveyor stops.
When the encoder detects that the target position has been reached, the machine stops moving.
This is the basic logic of PLC control.
IV. How Does a PLC Work?
The working principle of a PLC can be summarized in one sentence:Read signals → Execute program → Send output commands → Repeat continuously.This process is called the PLC scan cycle.
Step 1: Input Scan
First, the PLC reads the status of all input devices, such as whether a button is pressed, whether a sensor detects an object, or what the current encoder position is.
Step 2: Program Execution
Then, the PLC executes the program and makes decisions, such as starting a motor, stopping a machine, or triggering an alarm.
Step 3: Output Refresh
Finally, the PLC sends output commands to motors, valves, relays, or other devices to complete the action.
This cycle repeats continuously, usually within milliseconds, allowing machines to operate automatically and reliably.
V. How Does a PLC Work with Encoders?
The PLC controls the machine, while the encoder provides feedback on position, angle, speed, or displacement.
For example, in a motor control system, an encoder can be installed on the motor shaft to provide real-time position and speed feedback. The PLC uses this data to determine whether the machine has reached the correct position.
In linear motion control, a draw-wire displacement sensor can measure movement distance and send the signal to the PLC.
Therefore, PLCs, encoders, and displacement sensors are often used together to achieve more accurate automation control.
VI. PLC in One Sentence
A PLC is the control core of an industrial automation system. It receives signals, executes logic, and controls machines to complete automatic actions.
If an automated machine is compared to a human body, the PLC is the brain, sensors and encoders are the eyes and nerves, and motors, valves, and cylinders are the hands and feet.
VII. How BriterEncoder Supports PLC Control Systems
For 0–5 meter industrial stroke measurement applications, Briter Encoder meets core functional requirements while providing an ultra-thin no-guide-wheel structure, split-type maintainable design, and flexible installation adaptability—offering a more cost-effective optimization solution for engineering projects.
This is not merely a substitution, but an engineering-driven optimization and upgrade based on real project requirements.
In a PLC control system, accurate feedback signals are very important.
BriterEncoder provides rotary encoders and draw-wire displacement sensors for position, angle, speed, and displacement measurement.
Our products support multiple output options, including RS485 Modbus RTU, CANopen, SSI, TTL/HTL, 0–5V, 0–10V, and 4–20mA, making them suitable for different PLC and industrial control systems.
If your machine requires position feedback, speed detection, angle measurement, or linear displacement monitoring, BriterEncoder can provide reliable sensor solutions for your automation system.
