Simple Anti Bag Snatching Alarm Circuit Diagram. The heart of this entire circuit anti bag snatching alarm is operational amplifier IC CA3140 (IC1), configured as a comparator. The two inputs (inverting and non – inverting) is given to pin no 3 and 2 of operational amplifier respectively and output is obtained from pin no 6. Here IC2 (timer IC NE555) is used as monostable multivibrator. The timing component of anti bag snatching alarm is R5, VR1, and capacitor C2 with the given value in this circuit diagram lets the time of timer is about 1 minute.
For audio section, IC3 is used as alarm tone generator with an inbuilt oscillator. Finally the output is obtained from pin no 3 of IC3 and amplified by transistor T1 in order to get desire level and lastly fed to loudspeaker for output.
Simple Anti Bag Snatching Alarm Circuit Diagram
PARTS LIST
Resistors (all ¼-watt, ± 5% Carbon)
R1, R2, R3 = 100 KΩ
R4, R6 = 10 KΩ
R5 = 10 MΩ
R7 = 330 Ω
R8 = 220 KΩ
R9 = 1 KΩ
VR1 = 10 MΩ
Capacitors
C1, C3 = 0.0047 µF
C2 = 4.7 µF/16V
C4 = 0.01 µF
Semiconductors
IC1 = CA3140 (operational amplifier)
IC2 = NE555 (timer IC)
IC3 = UM3561 (complex ROM with an inbuilt oscillator)
T1 = BD139
ZD1 = 3.3V 500mA
Miscellaneous
SW1 = ON/OFF switch
L1 = speaker 8Ω 1W
Mono plug, mono jack 8
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