Active IR Motion Detector Circuit

Here’s the circuit that can be used to detect motion in an area where there are not supposed to be any moving objects using ultrasonic motion detector. This type of motion detector is most commonly used in burglar alarm systems since they are very effective in this application. This is the figure of the circuit;

There are tw1o transducers: one emits an ultrasonic wave and the other picks up reflections from the different objects in the area. The reflected waves arrive at the receiver in constant phase if none of the objects in the area are moving. If something moves, the received signal is shifted in phase. A phase comparator detects the shifted phase and sends a triggering pulse to the alarm.