Why some motors use encoders

2021-11-19 10:53

An encoder is a device that compiles and converts a signal (such as a bit stream) or data into a signal form that can be used for communication, transmission, and storage. The encoder converts angular displacement or linear displacement into electrical signals. The former is called a code wheel and the latter is called a code ruler. Encoders can be divided into two types: contact type and non-contact type according to the reading mode; encoders can be divided into two types: incremental type and absolute type according to the working principle. The incremental encoder converts the displacement into a periodic electric signal, and then converts this electric signal into a counting pulse, and the number of pulses is used to indicate the magnitude of the displacement. Each position of the absolute encoder corresponds to a certain digital code, so its indication is only related to the start and end positions of the measurement, and has nothing to do with the middle process of the measurement.
Encoders are mainly used in CNC machinery linked to the computer, and generally use ordinary motors to configure the encoder. The main purpose of the encoder is speed measurement and positioning.
The working principle of the encoder is: after the encoder generates an electrical signal, it is processed by a digitally controlled computer gong, a programmable logic controller, and a control system. These sensors are mainly used in the following areas: machine tools, material processing, motor feedback systems, and measurement and control equipment. The conversion of angular displacement in the encoder adopts the photoelectric scanning principle. The reading system is based on the rotation of a radial index plate, which is composed of alternating light-transmitting windows and opaque windows.
This system all uses an infrared light source to illuminate vertically, so that the light projects the image on the plate onto the surface of the receiver, which is covered with a layer of grating, called a collimator, which has the same window as the optical disc. The job of the receiver is to feel the light change produced by the rotation of the disc, and then convert the light change into a corresponding electrical change. Generally, a rotary encoder can also get a speed signal, which has to be fed back to the inverter to adjust the output data of the inverter.
Encoders are generally divided into incremental and absolute encoders, and they have the biggest difference: In the case of incremental encoders, the position is determined by the number of pulses calculated from the zero mark, while the position of absolute encoders is Determined by the reading of the output code. In a circle, the reading of the output code of each position is unique; therefore, when the power is disconnected, the absolute encoder is not separated from the actual position. If the power is turned on again, the position reading is still current and valid; unlike the incremental encoder, the zero mark must be searched for. Now the encoder manufacturers produce a complete series, which are generally dedicated, such as elevator dedicated encoders, machine tool dedicated encoders, servo motor dedicated encoders, etc., and the encoders are all intelligent, and there are various types of encoders. The parallel interface can communicate with other devices.
Why do some motors use encoders? Because the encoder can be used for speed measurement and positioning. Sending the encoder data to the computer makes it easier to understand some problems of the motor during operation for subsequent research or other purposes.

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