Encoders are devices used in many automation industries. You may have never noticed, but Encoder is always there. Today plctop.com will learn about Encoder with you.
1. What is Rotary Encoder?
An encoder, also known as an encoder, is a mechanical motion sensor that generates a digital signal in response to motion. An electromechanical device capable of converting motion into a digital signal or pulse. Encoder helps to measure and display the parameters of the machine’s speed.
There are two types of encoders: linear and rotary. Linear encoders respond to motion along a path, while rotary encoders respond to rotational motion.
2. Classify
+ Absolute Encoder: Called absolute, it means that the signal we receive from the Encoder indicates its exact position without the user having to process anything further.
- Use the disc in binary or Gray code.
- Has a structure including: light emitter (LED), encoder disk (containing signal ribbon), a light receiver sensitive to emitted light.
- Encoder disk is made from transparent material, the disc surface has been divided into equal angles and concentric circles.
- Advantages: keep absolute value when power is lost.
- Disadvantages: high cost because of complicated manufacturing, difficult to read signal
+ Incremental Encoder: emitting an ascending or cyclical signal
- The encoder consists of a pulsed band, usually divided into several equally spaced holes.
- The material can be transparent to allow light to pass through.
- Only 1,2 or maximum 3 holes, and usually with an extra locating hole.
- Disadvantage: prone to pulse deviation when returning. Errors will accumulate with long-term operation.
- Advantages: low cost, simple fabrication, easy signal processing.
3. Structure of Encoder
+ Encoder main structure includes:
- The circular optical disc has a small slot that rotates around the axis: On a perforated (groove) disc, when this disc rotates and shines an LED on the surface of the disc, there will be an interruption. The grooves on the disc divide the 360o circle into equal angles. And a disc can have multiple tracks from the circular center.
- Photosensor
- Light source.
+ Working principle of Encoder
When the disc rotates around the axis, there are grooves on the disc for the optical signal to shine through (Led). Where there is a groove, light can pass through, where there is no groove, light cannot penetrate. With the signal yes/no, it is recorded whether the LED shines through or not.
The number of Encoder pulses is conventionally defined as the number of times the light passes through the slit. For example, on a disk with only 100 slots, for every 1 revolution, the encoder counts 100 signals. This is the operating principle of the basic Encoder, but for many other types, of course, the rotating disc will have more holes and the received signal will also be different.
The light-collecting sensor will turn on and off continuously, from which:
- Generates square pulse signals.
- The pulse signal will be transmitted to the central processor to measure and determine the position / speed of the motor.
4. Encoder Application
+ Applications about speed indication:
When a pump is connected to the inverter to pump liquid into the tank. Then the liquid flowing into the tank must have a certain speed. The encoder connected to the inverter will respond to the actual flow rate of the liquid.
+ Measurement application:
When we need to cut aluminum coils hundreds, thousands of meters long into sheets of certain size through cutting machines. The encoder will then be installed on the conveyor, reading the material each time it passes through it and calculating the length of the aluminum sheet from when it is inserted to the cutting position. The cutter can be adjusted to the required length through the aluminum sheet size parameters.
+ The application of counting the number of products:
The encoder installation in the program of the product conveyors. It will help us to confirm each bottle of product entering and station on the conveyor belt. If the bottles do not leave the station within the programmed time and do not match the value counted by the encoder. It also means that the machine has been damaged.
+ Applications in mechanical engineering:
Talking about the structure of the CNC machine, the encoder is equipped as a device to help measure and determine the most accurate position of the machine axes as well as the position of the cutter. Therefore, when using CNC machines for machining, the most accuracy will be achieved. Moreover, through the recorded encoder, it will inform the control system of the PLC. From there, the user can adjust the cutting position to limit errors.
+ Applications in industries:
- Cars: Used as a mechanical motion sensor, can be applied to control speed.
- Consumer electronics and office equipment: Used as PC based devices, printers and scanners.
- Industry: Used in labeling, packaging and machine building machines with single and multi-axis motor drives.
- Medical: Used in medical scanners, microscopic or nanoscopic motion control of automated devices and dispensing pumps.
- Army: Used in positioning antenna application.
- Scientific instruments: Scientific instruments implement encoders in the positioning of observational telescopes.
So we have learned about Encoder, thank you for reading the article.
