Infrared anti-theft alarm circuit

The infrared reflective anti-theft alarm uses a reflective infrared detection component (the maximum detection distance is up to 12m) to trigger the alarm. When
a theft is detected, the alarm will emit a realistic dog barking sound to remind the owner that "there is an outsider." Invasion".
    (1) Circuit composition The circuit of the infrared reflective anti-theft alarm is composed of a power supply circuit, an infrared detection circuit, a voice generator and an audio amplifier
output circuit, as shown in the figure. The power circuit consists of power transformer T, rectifier bridge stack, filter capacitors C4, G and three-terminal voltage stabilizing
integrated circuit 7812.
    The infrared detection circuit is composed of infrared reflective detection module IC1, resistor Ri, and voltage stabilizing diode VSI.
    The sound effect generator is composed of sound effect integrated circuit IC2, resistor Rz, wind and Zener diode VS2.
    The audio amplification output circuit is composed of the audio power amplification integrated circuit IC3, capacitors C]~G, G and speaker: B.
    (2) Working principle of the circuit: After the AC 220V voltage is stepped down by T, bridge rectified, and filtered by C6, one channel provides 15v pulsating DC
voltage to IC3; the other channel provides IC1 with 12V working voltage and +12V voltage after being stabilized. After the island current limiting voltage and VS2 voltage stabilization,
it provides +3V working voltage for LC2.
  Under normal circumstances, IC1 outputs low level. IC2 cannot be triggered and the speaker BI. does not produce sound. When an outsider enters the alert detection
area of ​​IC1. The infrared signal emitted by Ki is reflected back by the human body.
  After IC1 receives the infrared signal reflected back from the human body and processes the signal, it outputs a high-level trigger signal, causing IC2 to be triggered to work and
output an audio signal. After the electrical signal is amplified by IC7, it drives BL to make a loud barking sound to remind the owner that "something abnormal" has occurred.