Four-digit electronic combination lock. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Four-digit electronic combination lock. 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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A simple circuit for an electronic combination lock of a combination of four buttons can be assembled on two microcircuits according to the RS flip-flop circuit.

Four-digit electronic combination lock

Due to the use of CMOS chips, this circuit draws a few microamps of standby current and operates in the voltage range from 3 to 18 volts. The circuit is assembled on two K561TL1 microcircuits or an analogue CD4093 AB. The four RS flip-flops work in series.

The combination of the lock corresponds to pressing the buttons S1, S2, S3, S4 in sequence and on the pin. 9-11 DD2 log "0" appears. If the sequence of dialing the code is incorrect, or if the S5-S12 buttons are pressed, all triggers switch to their original state. The circuit also eliminates the possibility of triggering if all buttons are pressed, because. triggers will go into disable mode.

Resistors are connected to the R and S inputs in the circuit for the stable operation of triggers, as well as the exclusion of tripping to static voltage. They are necessary, their resistance should be approximately the same.

For stable operation of the circuit, the power supply must be constant. On the output 9-11 DD2 can be connected through a resistor to a pnp transistor and an actuator, or a pulse shaper to drive a car central lock.

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