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Introduced An Infrared Motion Detector

2017-08-15 15:44  
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Figure 1 shows the main advantages of the ultrasonic motion detectors is that they are very sensitive and extremely fast performance. But it is sometimes normal reaction may lead to an environmental vibration car or an airplane passing overhead. There tw1o sensors : an issue reflected ultrasonic waves and other pick up different objects in the area. Reflected wave reaches the receiver if no object in the stationary phase of the movement area. If there is any movement, the received signal transfer phase. A phase comparator detects the phase shift and sends a trigger pulse alarm. Passive infrared motion detector in passive infrared motion detector, sensor contains an infrared-sensitive phototransistor is placed in the area of ??protection. Circuit in the sensor detects infrared radiation intruder's body and triggers the alarm. In order to prevent this type of detector is that it can cause an error or other interference with the warm air flow can change the level of infrared radiation areas, the new system tw1o infrared sensors monitor different regions protected area. If a person walked the protected area, the internal logic system triggers an alarm only when tw1o regional activation order.figure1a active ir motion detector


Active Infrared Motion Detector
figure2a active ir motion detector

Each sensor is made as shown in the active system tw1o shell. A housing containing an infrared emitting diode and an infrared-sensitive phototransistor. Other housing includes an infrared reflector. When positioned in front of an entrance, a protected area, tw1o shell build an invisible beam. A person entering the area interrupt causes an alarm clock, the beam is triggered. An active motion detector is more reliable than a passive one, but it needs to be carefully aligned when it is installed. Detector can trigger an error if one of the shell moving slightly and caused no continuous beam. Build a motion detector ignores ambient light. This type of motion detector using the same basic concept as the active infrared motion detector. An interrupt at 5kHz modulation pulsed beam by infrared diodes and transistors will receive infrared alarm.

figure3a active ir motion detector

Figure 3. Ambient-Light-Ignoring Active Motion Detector


As shown in IC2A C1 and L1 by op amp feedback loop causes only those frequencies at or near the LED 5 kHz modulation rate. IC2B increased output when a signal is received enough to put a negative voltage is below the reference set consists of C2 R2. On the left of this circuit is a transmitter circuit 5 kHz modulated infrared beam. As you can see from the principle of the receiving circuit, the resonant tuned narrowband amplifier reduces the sensitivity of the detector to the stray light. The output of this circuit then attach some load resistor, can call the police or demonstration purposes, LED.