INFRARED MOTION DETECTOR CIRCUIT

1. Here is the circuit diagram of an infrared motion detector that can be used to sense intrusions.
2. Infra red rays reflected from a static object will be in one phase, and the rays reflected from a moving object will  be in another phase.
3. The circuit uses this principle to sense the motion.
4. The IC1 (NE 555)  is wired as an astable multivibrator .
5. The IR diode connected at the output of this IC produces infrared beams of frequency 5Khz.These beams are picked by the photo transistor Q1.
6. At normal condition ie; when there is no intrusion the output pin (7) of IC2 will be low.
7. When there is an intrusion the phase of the reflected waveforms has a difference in phase and this phase difference will be picked by the IC2.
8. Now the pin 7 of the IC 2 goes high to indicate the intrusion.An LED or a buzzer can be connected at the output of the IC to indicate the intrusion.

         NOTES:

• Comparators IC2a and IC2b are belonging to the same IC2  (LM1458).So the power supply is shown connected only once.No problem.
• When there is disturbance in the air or vehicles passing nearby,the circuit may get false triggered.
• POT R5 can be used for sensitivity adjustment.