Size: 82 x 44mm
Texture of material: Two-sided 1.6mm FR-4 board
Long life Low ESR
Pyroelectric infrared sensor security circuit consists of pyroelectric infrared sensor PIR, integrated operational amplifier LM358, voltage comparator LM393, 110 alarm circuit and boot delay circuit, etc.. The circuit can be used as home security. When the family leaves the room, the switch K1 is closed, the circuit starts to work. As long as someone enters the room after a period of time, it will sound alarm.
1. The circuit is energized, the pyroelectric infrared signal of infrared sensor PIR to detect the front radiation of human body, from the signal PIR 2 feet output weak, after amplification transistor VT1, through the C2 input to the op amp IC2A 3 foot high gain low noise amplifier, and then by IC2A the "1 foot" output signal.
2. IC2B in the circuit as a voltage comparator, its "5" pin voltage reference is provided by R10, VD1, IC2A when the "1" foot output signal to the IC2B "6" feet, "5" and "6 foot" input voltage is compared, if at this time the "6 foot" voltage ratio 5 feet high, 7 feet of IC2B from high level to low level. The C6 through the VD2 discharge, the IC3 2 feet into low level, if the voltage reference voltage of 2 feet "than" 3 "feet of a resistance R14, partial pressure of R15 with low IC3, the" 1 foot "into a high VT2 transistor conduction music chip IC4 the" 2 foot "voltage, output audio signal after amplification transistor VT4, buzzer driver BELL issued 110 alarm sounds.
3. When people leave the detection area, IC2B's "7" feet to high, VD2 cut-off, C6 has a charging time (30 seconds), making the buzzer delay alarm for 30 seconds.
4. VT3, R20 and C7. The time delay circuit, about 2 minutes (should be greater than the alarm delay time), to prevent the alarm immediately when starting up, let people have time to leave the scene, but also can prevent misoperation in power after the call.
1 x DIY pyroelectric infrared sensor kits