Improved doorbell circuit

This article introduces a music doorbell that does not require buttons. As long as the visitor stands in front of the doorbell, the doorbell will automatically sound. The circuit principle of the music doorbell is shown in the attached figure:

IC1 and other components form an infrared transmitting circuit. IC1, RP, R1, and C1 form a multi-vibration frequency. According to the component data shown in the figure, the oscillation frequency is about 40kHz, and the output current is 100--200mA, which can drive the infrared light-emitting diode D1 to emit a 40kHz modulated infrared pulse. IC2 is an infrared receiving chip with high sensitivity, high gain, good output waveform, and frequency discrimination function. After receiving the infrared pulse with a frequency of 40kHz, the infrared receiving tube D2 converts it into an electrical signal and sends it to the 7th pin of IC2. After amplification, C5 and L tuning, and IC2 internal circuit detection and shaping, the pulse signal is output from the 1st pin.