Security device with independent power supply. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Security device with independent power supply. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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In [1], my note about a security device powered by AC was published. I made such a device for my friend, but it did not justify itself. Knowing about the existence of a security device, the attackers simply de-energized the network at home and stole a number of products.

This hurt my ego, and I made a self-powered security device. The result was not long in coming. Before the New Year, the alarm went off, and the villains were caught red-handed.

A schematic diagram of a device for three security loops (although their number can be increased by adding one diode, one LED and one socket for each new direction) is shown in Fig. 1.

Security device with independent power supply

The microbutton for controlling the corresponding doors is connected to the socket. When the door is opened, the button closes. Closing the button leads to the supply of minus power through the corresponding diode (VD1-VD3) to the multivibrator circuit on transistors VT1, VT2. The multivibrator starts generating a signal in the audio frequency range. Through the current amplifier on the transistor VT3, the signal is fed to the telephone capsule TC. An audible alert sounds. At the same time, the corresponding LED lights up, signaling which door is open. A feature of the circuit is that in standby mode it does not consume current from the power source.

Figure 2 shows the printed circuit board of the device, and Figure 3 shows the location of the elements on the printed circuit board. The device uses germanium diodes and transistors, although it may well work on silicon.

Security device with independent power supply

References:

Shadykhanov B.S. Burglar alarm for yard utility rooms//Electrician. - 2003. - No. 11. - P.10.

Author: B.S. Shadykhanov

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