System Block Diagram
The system uses the RE200B pyroelectric sensor as the signal detector. When movement is detected, the sensor generates an electric signal of approximately 0.5V. This signal is then rectified and filtered before being sent to the amplification stage. The amplifying circuit consists of a two-stage operational amplifier, which boosts the signal to around 3.8V and sends it to the signal processing circuit. In the signal processing stage, the input signal is compared with a reference signal from pin 9 using an AND gate. Since pin 9 is connected to a high-resistance network, it remains at a constant high level. As a result, when motion is detected, the signal processing circuit outputs a high-level signal that is passed to the delay circuit. The delay circuit is made up of a resistor and capacitor in series. After a set time, the output triggers a transistor, which in turn activates the alarm circuit. This ensures that the alarm is only triggered after a certain period, reducing false alarms caused by brief movements.
RE200B Physical Map
RE200B Schematic
The RE200B is a pyroelectric infrared sensor that detects changes in infrared radiation without direct contact. It uses the polarization properties of pyroelectric materials and employs a dual-sensitivity complementary method to reduce interference from temperature fluctuations, improving overall stability. The sensor outputs an electrical signal through pin 2 when detecting changes in infrared energy. To ensure signal stability, a 47kΩ resistor and a 0.1μF capacitor are connected to the output pin. These components help to rectify and filter the signal, minimizing noise and interference.
Biss0001 Secondary Amplification and Delay Circuit
The BISS0001 is a high-performance signal processing integrated circuit used in conjunction with the RE200B. It allows for quick activation of a buzzer when motion is detected. The chip includes a two-stage operational amplifier, a logic circuit, a lockout timer, and a delay timer. When the RE200B detects movement, it outputs a 0.4V signal, which is then processed by the BISS0001. After rectification and filtering, the signal is amplified by the internal op-amp. The sensitivity of the sensor is adjusted by the resistor and capacitor on pin 15. In this experiment, a 47kΩ resistor and a 47μF aluminum electrolytic capacitor were used, allowing the sensor to detect movement up to 1 meter away. After two stages of amplification, the signal reaches 3.8V and is compared with the reference signal from pin 9. Since pin 9 is connected to a high-resistance network, it remains at a constant high level. This comparison results in a high-level output that is sent to the lockout and delay timers. The delay timer produces a high-level output for a set duration (TX ≈ 49152 × R1 × C1), while the lockout timer prevents any further triggering during this period. In this experiment, R1 was 47kΩ and C1 was 10nF, resulting in a delay of approximately 23 seconds. The lockout time (TI) was about 0.012 seconds, ensuring no interference during the delay period. Finally, the signal is sent to a voltage divider, which turns on a transistor and activates the buzzer.
The alarm circuit includes a power supply, a transistor, and a buzzer. The buzzer is connected between the collector of the transistor and the positive terminal of the power supply (5V). The emitter is connected to the negative terminal, and the base is linked to the BISS0001 chip. When the chip detects motion, it outputs a 3.8V signal through a voltage divider, which turns on the transistor and triggers the buzzer.
This experiment simulates the design of a pyroelectric sensor alarm. The RE200B sensor is used along with the BISS0001 chip for testing. When the sensor detects infrared movement, it sends a high-level signal to the BISS0001. Because pin 9 is connected to a high-resistance network, it remains at a high level, allowing the BISS0001 to detect the signal and trigger the buzzer. This setup provides a reliable and effective motion detection and alarm system.
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