Code lock with alarm. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Safety and security
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This design (see figure) differs from similar ones in that in case of an attempt to open the door by unauthorized persons, it is equipped with an audible alarm for incorrect code entry.
When the supply voltage is applied, the R1C1 circuit sets the DD1 trigger to zero and the inverse pin 6 of the DD1 chip is high. When the buttons SB7-SB9 are pressed at the same time, a signal is sent from this output to the actuator, which consists of a transistor amplifier and a traction solenoid that controls the lock bolt.
If the lock code is dialed incorrectly, i.e., any of the buttons SB1-SB6 is pressed, a high level appears at pin 8 of the microcircuit. The trinistor VS1 opens and turns on the buzzer - it is made on a symmetrical multivibrator (transistors VT1, VT2), a power amplifier (VT3) and a dynamic head (BA1) - it makes a sound. The signaling device is turned off and the device is reset by pressing the SB10 button.
The SB7-SB9 buttons can correspond to any keyboard buttons and form the corresponding code, for example, 196. The SB 1 -SB6 buttons are left on the keyboard. Button SB 10 set in a secret place or use instead, say, the button "0" of the keyboard.
Transistors can be any of the series indicated on the diagram, trinistor - KU101 series with letter indices G, E, I, it can also be replaced with a transistor of the same type with VT1, VT2. Capacitors - K50-3 and KM-6, resistors - MLT, dynamic head - any with a voice coil with a resistance of 4 - 8 ohms. Power source - a rectifier or a battery of galvanic cells with a voltage of 6 V at a load current of at least 100 mA.
If the buzzer does not turn on when checking the device, you will have to select a trinistor.
Author: G.Dutsarev, Losino-Petrovsky, Moscow region.
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