Abstract : With the development of science and technology, low-voltage electrical technology has been widely applied to various fields of coal mines, promoting the development of coal mine production. The TYDM type automatic gangue removal device integrates sensors, transmitters, microcontrollers, and frequency converters, adapting to the requirements of coal preparation and meeting production needs. This paper introduces the main design principles, characteristics, and improvement methods of the TYDM type automatic gangue removal device. Keywords : jig; transmitter; microcontroller; frequency converter. Zhangshuanglou Coal Mine's coal preparation plant uses a mechanical moving screen jig for coal preparation. The jig uses the reciprocating motion of the screen plate in water to separate gangue and clean coal from the raw coal. The heavier gangue falls to the bottom of the moving screen, forming a gangue layer; the lighter clean coal is discharged from the upper outlet, and the gangue is discharged from the installed gangue removal wheel device. The thickness of the gangue layer and the gangue removal speed directly affect the quality of coal preparation. If the gangue removal speed is fast, the gangue layer becomes thinner, and clean coal is discharged from the gangue outlet, containing clean coal. If the speed is too slow, the gangue layer formed is too thick, and gangue is discharged from the clean coal outlet, containing gangue. Only when the gangue removal speed is moderate and the separation effect of clean coal and gangue is good can the quality of coal preparation be guaranteed. The "TYDM type automatic gangue removal device" (hereinafter referred to as the device) designed and developed by Shenyang Institute of Automation has solved this problem well. [align=center] Figure 1 Composition of TYDM type automatic gangue removal device [/align] [b]1 Composition of the device[/b] The device consists of four parts: gangue layer thickness detection link, gangue wheel speed control link, power drive link, and actuator, as shown in Figure 1. 1.1 Gangue Layer Thickness Detection Stage The gangue layer thickness detection stage consists of a buoy, a differential transformer-type displacement sensor, and a transmitter. After calculation and adjustment, the relative density of the buoy is less than that of the gangue but greater than that of the clean coal. The iron core moves up and down inside the displacement sensor, and the transmitter converts this into a 4-20mA current signal for the gangue wheel speed control stage. The differential transformer-type displacement sensor is manufactured using the principle of a differential transformer. It can directly convert linear mechanical movement into electrical changes and consists of a primary winding and two secondary windings. After the primary winding is connected to an AC power supply, mutual inductance causes the two secondary windings to generate induced electromotive forces (EMFs). Connecting the corresponding terminals of the two secondary windings yields a characteristic curve at the other pair of corresponding terminals that has a linear pole number relationship with the iron core displacement. When the induced EMFs of the two secondary windings are not equal, a voltage output occurs, the magnitude and phase of which depend on the magnitude and direction of the iron core displacement. The transmitter can directly provide the required sinusoidal excitation magnetic source for the AC differential transformer-type displacement sensor, and simultaneously demodulate the sensor's output voltage signal, proportional to the displacement, into standard current and voltage signals to adapt to the automatic control system for displacement measurement. The detection process is shown in Figure 2. [b][align=center]For more details, please click: Application of TYDM Type Waste Discharge Device in Dynamic Screen Jig[/align][/b]