As shown in the figure, the music type refrigerator closes the reminder circuit. The circuit consists of step-down rectifier regulator circuit, delay circuit, music integrated circuit CIC2851E, speaker and other components. The step-down rectifier regulator circuit provides a DC voltage of about 3V for the entire circuit. When the refrigerator door is opened, the switch AN is turned on and the capacitor C3 is charged through R3. As the charging progresses, the base potential of BG1 rises, and after approximately 20 minutes of delay, the voltage on C3 turns on BG1 and BG2 turns off. Correspondingly triggering the work of CIC2851E, its output music signal is amplified by BG3 and then drives speaker Y to send a song called “The bell whistle...†to remind the owner to quickly close the door. If the refrigerator door is not closed, the music will not stop. The length of the delay can be selected according to the time of access to food, generally between 5 to 15 seconds. This circuit takes 20 seconds. In the circuit, the voltage across the DW is required to be about 3V. If it is too high, the integrated circuit is easily damaged. Resistor R6 is used to adjust the speed of the music rhythm, and its value range is 20kΩ≤R6≤120kΩ. Displacement sensor, also known as linear sensor, is a linear device belonging to metal induction. The function of the sensor is to convert various measured physical quantities into electricity. In the production process, the measurement of displacement is generally divided into measuring the physical size and mechanical displacement. According to the different forms of the measured variable, the displacement sensor can be divided into two types: analog and digital. The analog type can be divided into two types: physical property type and structural type. Commonly used displacement sensors are mostly analog structures, including potentiometer-type displacement sensors, inductive displacement sensors, self-aligning machines, capacitive displacement sensors, eddy current displacement sensors, Hall-type displacement sensors, etc. An important advantage of the digital displacement sensor is that it is convenient to send the signal directly into the computer system. This kind of sensor is developing rapidly, and its application is increasingly widespread. Magnetic Dro Scales,Ditron Magnetic Scales,Magnetic Linear Scale,Electronica Magnetic Scales Changchun Guangxing Sensing Technology Co.LTD , https://www.gx-encoder.com