Touchless Doorbell For The Post-Covid World

The Touchless Doorbell circuit uses an infrared-based proximity detection method to trigger a chime without requiring physical contact. At the heart of the system is an IR transmitter LED that continuously emits infrared light, paired with a TSOP1738 IR receiver designed to detect modulated IR signals at 38 kHz. When a visitor places their hand near the sensor, the emitted infrared light reflects off the hand and strikes the TSOP1738 receiver. Upon receiving this reflected signal, the receiver changes its output state, which acts as a trigger signal for the circuit. This trigger is fed into an NE556 dual timer IC configured to control the timing and pulse duration of the activation signal. The output of the timer switches a BC547 transistor into conduction mode, allowing current to flow through the coil of a 12V single-changeover relay. When the relay energizes, its switch contacts close to complete the circuit for an external doorbell or chime mechanism. The system is powered by a 12V DC power supply, regulated and protected locally using components such as a 5.1V Zener diode and a rectifier diode to safeguard sensitive IC pins and prevent back-EMF spikes during relay switching.