Electronic combination lock eight

This example introduces an electronic password lock made of CD4044 digital integrated circuit and a small number of peripheral components. It has the characteristics of simple circuit, easy production, low cost, reliable confidentiality, etc. It can be used in security doors, safes, file cabinets, etc. Electronic control.
Circuit Working Principle
The electronic password lock circuit consists of a password input control circuit and a control execution circuit, as shown in Figure 3-105.

The password input control circuit is composed of password buttons S1-S10 (S1-S4 are valid passwords, S5-S10 are invalid passwords), RS trigger integrated circuit IC, resistors R1-R5 and capacitors Cl-C5.
The control execution circuit is composed of diodes VDl-VD4, resistor R6, transistors Vl, V2 and electromagnet YA.
C6 and C7 are power supply filter capacitors.
S1-S4 are respectively connected to the set terminals (S1-S4 terminals) of the four RS flip-flops in the IC, and S5-S10 are connected in parallel to the four reset terminals (Rl-R4) of the IC. The IC is in the reset state, and its Ql-Q4 output terminals all output low level, VDl-VD4 are all turned on, Vl and V2 are cut off because the base of Vl is extremely low, and the electromagnet YA is in the release state (the electronic password lock is locked state).
When the S1-S4 buttons are pressed, low-level pulses are applied to the S1-S4 terminals of the IC, causing the four RS flip-flops to be triggered and set. The Ql-Q4 terminals of the IC all output high levels, causing VDl-VD4 All are cut off, and after the base of Vl changes to a high level, Vl and V2 are turned on, and the electromagnet YA is attracted to open the electronic lock.
When entering the password, if any button 55-510 is pressed by mistake, all four RS triggers will be forcibly reset, the Ql-Q4 output terminals of the IC will all become low level, and the electronic lock cannot be opened. While the RS flip-flop is forced to reset, the pressed invalid button (error button) of C5 is quickly discharged. After releasing the invalid button, the +6V voltage charges C5 through R5 (with a delay of about 10s). Before C5 is fully charged, the IC is in a locked state. Pressing any button in this state is invalid. Therefore, the code lock can be opened only by pressing the four unlock code buttons S1-4 accurately.
In order to enhance the confidentiality of the electronic combination lock, the distribution order of 4 valid passwords and 6 invalid passwords can be arranged in any order.
Component selection
Rl-R6 uses 1/4W carbon film resistor or metal film resistor.
Cl-C4 and C6 use monolithic capacitors or polyester capacitors; C5 and C7 both use aluminum electrolytic capacitors with a withstand voltage of 16V.
VDl-VD4 use 1N4148 silicon switching diodes.
Vl uses S9013 or S9014 silicon NPN transistor; V2 uses C8050 or S8050, 3DG8050 silicon NPN transistor.
The IC uses the CD4044 type four-R smart flip-flop integrated circuit.
S1-S10 all use micro-action (normally open) buttons or use the combination keypad switch of a fixed telephone instead.