Automatic doorbell production circuit

Circuit working principle: It consists of an infrared light-emitting diode sending unit, a receiving unit and
a buzzer unit. The infrared LED sending unit and receiving unit are installed
on both sides of the doorpost of the entrance, so that the infrared beam emitted by the infrared LED can directly fall
on the receiver. The buzzer should be installed indoors. When someone passes through the gate entrance,
the buzzer sounds immediately because the infrared rays falling on the receiver are interrupted. The circuit is
very simple, it consists of 5 V voltage regulator IC 3 (7805), infrared sending unit IC.
(TLC555), infrared LED , infrared receiver IRX, (TSOP1738), monostable circuit
IC2 (4538), relay drive transistor VT, relay RL, and buzzer
PZ. S. The automatic doorbell circuit can be turned on or off , and the LED indicates that the automatic doorbell is
in standby mode. In the sending unit, IC1 is connected to a multivibrator with an operating frequency close
to 38 kHz. The specific frequency is determined by RP1, R1, and C1. The output pulse of the IC
drives the infrared LED, and R2 is the current limiting resistor of the infrared LED .