Thyristor code lock. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling
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When installing a combination lock, it is not always possible to place the keypad close to the control circuit. In this case, the use of thyristors as triggers that store the correct combination of the typed code provides higher noise immunity and resistance to deliberate damage compared to circuits assembled only on CMOS microcircuits.
The scheme shown in Figure 2-20 allows you to restrict access to the premises of outsiders. To trigger the YA1 solenoid that opens the latch, it is necessary to dial a code of 4 digits (out of 10 possible) in a certain sequence.
The scheme works as follows. In the initial state, a log 1 enters the control input D1 6/12 through the resistor R1 and the internal key of the microcircuit will be closed. Pressing the buttons in the sequence S4 S3 S2 S1 will lead to the sequential opening of the corresponding thyristors VS4, VS3, VS2, VS1. The current through the resistors R8 R10 allow you to keep the triggered thyristors in the on state. Moreover, if any other button is mistakenly pressed when dialing a number, this will lead to the operation of the key on the element of the D1 chip. 3 which will ensure the appearance of a log 0 at the input D1. 1/6 - the key will open and the partially correct code will be reset.
Fig. 2.20. Electrical diagram of the combination lock (click to enlarge)
Rice. 2.21. Scheme for replacing the transistor VT1
Rice. 2.22. PCB topology and element layout
With the correct dialing of the number, a current will flow through the resistors R6 R7 and the transistor VT1 will open. This will energize the electromagnet YA1. And so that the electromagnet is not energized for a long time after the operation of the element D1. 2, together with the charge circuit of the capacitor R11 C1, allows you to limit the duration of its operation to an interval of 24 s. The time is determined by the value of the capacitor C1. As soon as the voltage at the input D1 2/12 in the process of charging the capacitor reaches the threshold of the key, it will give the log "0" to the control D1.1, which will reset all thyristors to their original state.
The device can operate when the supply voltage changes within a wider range than indicated in the diagram, but its value is selected based on the value necessary for reliable operation of the applied electromagnet. When setting up the circuit, it may be necessary to select the values of the resistor R7 and capacitor C1.
Transistor VT1 has a high gain and can be replaced by two conventional ones included in the circuit shown in Fig. 2. 21. Thyristors can be used with any last letter in the designation. Capacitors are used K50 35 for an operating voltage of 40 V, and any resistors will fit.
The SB1 button is used to remotely open the lock indoors and must be rated for a current of 3 A.
Rice. 2.23. Connecting the exchangeable coding plug X2
All elements of the circuit, except for the transformer, VD5 VD8 diodes and YA1 electromagnet, are located on a single-sided printed circuit board, fig. 2.
For the convenience of changing the code and connecting the circuits from the dialing buttons, M2,5 screws are installed on the board (as shown in the figure), to which the desired wire is fixed. If you install an additional 16-pin connector (X2, Fig. 2. 23) with a replaceable code-setting plug, then changing the code will take a few seconds (if you prepare the plug with jumpers installed for the desired combinations of code numbers in advance).
Fig. 2.24. Time Limit Scheme
One of the elements of the microcircuit is not used and it can be used to limit the required time for typing the code, which further complicates the selection of the code. An example of such a connection D1.4 is shown in fig. 2.24.
Publication: cxem.net
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