Touchless door bell using LM358

A touchless doorbell is a smart and hygienic alternative to traditional push-button doorbells. This project uses an LM358 operational amplifier as a comparator to detect motion or proximity, allowing users to ring the doorbell without physical contact. It is especially useful in homes, offices, hospitals, and public places where minimizing touch is essential for hygiene.

Components Required:

1. LM358 Op-Amp – Functions as a comparator to process sensor signals.
2. IR Sensor Module or LDR (Light Dependent Resistor) – Detects motion or proximity.
3. Buzzer or Doorbell Circuit – Produces sound when triggered.
4. Transistor (BC547 or BC557) – Acts as a switch to activate the buzzer.
5. Resistors and Capacitors – For circuit stabilization.
6. Power Supply (5V or 9V Battery) – Powers the circuit.

Working Principle:

• The IR sensor continuously emits infrared rays. When a hand or object comes near, the reflected rays are detected by the sensor.
• The LM358 op-amp compares the sensor’s output with a reference voltage. If the proximity is detected, the op-amp output goes HIGH.
• This output triggers a transistor, which in turn activates the buzzer or doorbell circuit.
• Once the hand is removed, the circuit resets automatically, making it ready for the next use.

Applications & Benefits:

• Hygienic and Contactless, reducing germ transmission.
• Low-cost and easy to build, requiring minimal components.
• Energy-efficient, consuming very little power.
• Can be modified for advanced features like wireless control or voice assistance.