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

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This security device is also significantly different from previously published ones. As a sensor, a piezoelectric element from a pickup (or a ZP-1 ceramic emitter) is used, pressed or glued (preferably not completely, but only from one end) to the lock body, door, car body or other protected object.

(click to enlarge)

There can be several sensors connected in parallel. If the device is turned on and in standby mode, then the first light hit with a metal object on the object (an attempt to open the lock with a key or a master key, unscrew the wheel, etc.) will cause a packet of voltage pulses on sensor D. Amplified by transistors VT1, VT2, passing through the regulator sensitivity R5 and inverter D3.3, the first pulse of the package starts the one-shot on D1.1, D1.2. At pin 11 D1.1, a log "0" appears, which starts the generator of second pulses on the elements D1.3, D1.4. These pulses are fed to the input "C" D5. The counter switches, and a log appears alternately at outputs 1-9. "1".

If the second hit occurs during the second when the log. "1" is at output 4, then the log. "0" from pin 11 D3.1 will overturn the RS flip-flop on the elements D4.1, D4.2. At the input E "of the counter, a log. "1" will appear, prohibiting counting for the entire duration of the one-shot pulse (about 1 min.). During this time, the owner will open the lock and turn off the signaling device. If the second blow occurs at another time, the trigger will overturn on elements D4.3, D4.4, the counter will also stop, and at the same time the siren will turn on on elements D2.3, D2.4, D6 and VT3 - VT6. The main tone of the siren changes under the influence of second pulses.

When the single vibrator pulse ends, the siren will turn off, and a log will be sent to the input "R" of the counter. "1", which will reset the counter to its initial state. At the same time log. "0" from pin 10 D1.2 through the VD4 diode will also set both RS triggers to their initial state and the device will go into standby mode.

A single vibrator on elements D2.1, D2.2, launched by pressing the KN button, blocks the counter and makes it impossible to turn on the siren for a little more than a minute. This is necessary for the "silent" closing of the door. The second pulses coming through the VD10 diode to the siren amplifier cause clicks in the loudspeaker, making it easier for the owner to turn off the siren. Element D3.4 switches it off in standby mode, reducing the current consumption to 0,5 -1 mA.

The security device is mounted on a printed circuit board. The location of the parts is shown here. During installation, the microcircuits must be protected from static electricity. Pin 9 of the D3.1 chip can be connected to any of the 9 D5 outputs by setting your own version of the "key". All other outputs must be connected via diodes, as shown in the diagram. The finished board, together with the batteries, is installed in a suitably sized case. The KN button and power switch are mounted on top of the case.

If the prefix is ​​​​used to protect the apartment, then several dozen holes (3-6 mm) are drilled in the door, closed with a metal mesh (or a plate with the same holes), and a dynamic head is attached to it. The body of the device is attached to the door near the radiating head. The piezoelectric element is connected to the structure with a shielded or twisted wire.

Instead of the K561PU4 microcircuit, you can use the K176PUZ, instead of the rest from the 561 series, the same ones from the 176, 164 or 564 series. The device assembled from serviceable parts does not need to be adjusted. It is only necessary to set the required sensitivity with the resistor R5. If you lightly hit the lock with the key or try to insert it into the well, the pulse generator should turn on and clicks should begin to be heard at a frequency of 2 Hz. This means that the device has entered the second strike waiting mode. If everything is done as in the diagram, then you can turn off the siren by hitting the lock after the 8th click, that is, after 4 seconds. Hitting at another time will turn on the siren. To further complicate the "work" of the thief, you can remove the clicks by removing the VD10 diode, but then the owner will need to maintain the second rhythm himself.

Do not set high sensitivity to avoid false positives of the device.

How the device works:

1. Turn on the console and press the button.
2. Leave the house and close the door (you only have one minute!).
3. Returning, hit the key on the lock, count the required number of clicks and hit the lock again.
4. Open the door and enter the house (you only have 1 minute to disable the alarm call).

The security device can not be turned off, then you will be under protection at home, the batteries will last for several months.

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