Motion detection alarm using PIR sensor and LM358 IC

Circuit Design:

1. PIR Sensor Connections:
   • Connect the VCC pin of the PIR sensor to the positive supply voltage (e.g., 5V).
   • Connect the GND pin of the PIR sensor to the ground (GND) of the circuit.
   • Connect the OUT pin of the PIR sensor to the non-inverting input (pin 3) of the LM358.
2. LM358 Operational Amplifier Connections:
   • Connect the inverting input (pin 2) of the LM358 to the junction of two resistors forming a voltage divider. Connect one resistor (e.g., 10kΩ) to the output (pin 1) of the LM358 and the other resistor (e.g., 100kΩ) to the ground (GND).
   • Connect the junction of the resistors to the non-inverting input (pin 3) of the LM358.
   • Connect the output (pin 1) of the LM358 to the positive terminal of the buzzer or alarm output device. Connect the negative terminal of the buzzer to the ground (GND).
3. Power Supply:
   • Connect the positive terminal of the power supply to the VCC rail and the negative terminal to the ground (GND) rail of the circuit.

Working Principle:

1. PIR Sensor:
   • The PIR sensor detects infrared radiation emitted by or reflected from objects in its field of view.
   • When motion is detected, the PIR sensor outputs a high signal on its OUT pin.
2. LM358 Operational Amplifier:
   • The LM358 is configured as a comparator.
   • The voltage divider formed by the resistors connected to the inverting and non-inverting inputs sets a reference voltage.
   • When motion is detected, the PIR sensor’s high output causes the voltage at the non-inverting input to rise above the reference voltage, triggering the LM358 to output a high signal.
3. Buzzer/Alarm:
   • The high output from the LM358 activates the buzzer or alarm, producing an audible alert.