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Home > Circuit Diagram > Home Appliance Circuit > Anti-theft alarm circuit for valuable home appliances

Anti-theft alarm circuit for valuable home appliances

Source:tinyfire
2023-06-08 22:12:38 33

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KD-95613DG63AX31

Anti-theft alarm for valuable household appliances
This valuable home appliances anti-theft alarm has the characteristics of small size and loud sound. Suitable for home, hotel, government, etc.
- How it works
　　　　　　　　　　
The circuit principle is shown in Figure 1 (Fig.Click to download the schematic). SCR, R1 and AN constitute a thyristor trigger switch circuit. IC1, R2, VT1, VT2 and BL make up an analog flute sound circuit. Normally, AN is pressed by household appliances to disconnect the two normally closed contacts, SCR is blocked without trigger signal, and alarm does not work. When the household appliances are lifted, the AN contacts close automatically. The trigger end of the SCR gets trigger signal from the positive pole of the power supply through R1. The SCR conducts and the IC1 works on power. The alarm signal output from the output end of the SCR is amplified by the power of VT1 and VT2, which promotes loud alarm sound from the speaker. At this time, even if the home appliances are put back in place or AN is destroyed, the alarm sound cannot be stopped. The alarm can only be released if the owner turns on the switch S which is installed with the alarm and is difficult for others to find at the moment.
Component selection and fabrication
The list of components is shown in the table below.

Number
Name
Type number
Quantity
R1resistance4.7K
1
R2resistance240K
1
R3resistance10K
1
VT1Crystal triode3D G6, 9014, etc.
1
VT2Crystal triode3AX81, 9012, etc.
1
SCROne-way thyristor3CT2K, BT169 0.1A/50V-1A/400V
1
ICAudio integrated circuitKD-9561 or other similar products
1
ANThe micro switchNormal Closed Type
1
BLspeaker8
1
SPower switchToggle switch
1
EBattery pack4.5V
1

The alarm part can be installed in a plastic box and placed in a place where the alarm sounds can be easily heard (e.g. on duty). Use double strands of thin wires to guide AN to the home appliances placement, and place AN cleverly on the desktop, desktop or TV cabinet, etc. to ensure that AN can move correctly.

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