Rolling door anti-theft device

Rolling door anti-theft device

This highly sensitive vibration detection type rolling door anti-theft device can detect the mechanical vibration and sound around it, and immediately switch on the 60W light bulb and sound a warning alarm. After the anti-theft device is set to the standby state, the circuit automatically provides a 15-minute delay, so that the store owner has enough time to close the rolling door and leave.

Binary counter CD4060 (IC1) forms a timer, providing a 15-minute delay. After 15 minutes, resistors R3, R4 and capacitor C2 make IC1 output Q9 high, and diode D1 connected to Q9 makes the clock input pin (11) inactive. The high potential of Q9 can be maintained until the power is disconnected. The flashing LED1 indicates that the oscillator part in IC1 is working properly.

IC2 is connected as a monostable trigger, and its reset pin ④ is connected to Q9, so IC2 works normally. Transistor T1 amplifies the signal generated by the piezoelectric sensor PZ1 to trigger the monostable trigger IC2.

In the standby state, the alarm circuit IC3 remains in the sleep state (the output pin (3) of IC2 is at a low potential at this time).

When any mechanical vibration disturbs the piezoelectric element, IC2 is triggered, and its output becomes high and remains high for 3 minutes, triggering the bidirectional thyristor TRIAC1 (BT136) through R9, making the 60W bulb light up; and activating the alarm circuit IC3, producing a sound similar to a siren. This alarm state can last for 3 minutes. R11 is the oscillation control resistor of IC3. The voltage regulator diode ZD1 provides a stable 3.1V DC voltage for IC3.

The piezoelectric element is connected to the circuit with a single-core shielded wire, a rubber gasket is glued to the smooth surface of the piezoelectric element, and then the gasket is fixed to the door frame facing the rolling door. In this way, the piezoelectric element can flexibly detect external vibrations.