Using codes for the purpose of a security has been the popular trend recently. A similar type of electronic circuit is presented right below called electronic code lock which ensures the use of four digits in code locking process and these codes are keyed in remotely. The code can be unlocked easily by pressing the right keys and if, someone presses the wrong keys, it resets the lock automatically. The complete phenomenon of electronic code lock system has been described briefly in the second paragraph.
Circuit Description of Electronic Code Lock
In the circuit electronic code lock, the lock code is set through proper connection of line wires to the pads A, B, C and D as shown in the circuit diagram of electronic code lock. For clear understanding, an example might be more appealing. If the code is 1234, connect line 1 to A, line 2 to B, line 3 to C, line 4 to D and rest of the lines, 6, 7, 8, 9 are connected to the reset pad as shown by dotted lines in the respective circuit diagram.
The whole circuit of electronic code lock is built around two CD4013 (IC1 and IC2) dual-D flip-flop ICs. The clock pins of the four flip-flops are directly connected to A, B, C and D pads in the circuit. The condition for energization of relay RL1 in the circuit is realized by clocking points A, B, C and D in that order. The remaining five switches as mentioned in the example are connected to reset pad so that all the flip flops are reset. If the key pad switch (A/B/C/D) is touched, the clock input pin is briefly pulled high. As a result, the state of flip-flop is altered. The output pin of each flip-flop designated as in the circuit diagram is wired to the input pin of the next flip-flop designated as D, where as the D pin of the first flip-flop is connected to the ground. If correct sequence of pressing keys is followed, then low level appears at the output of IC2. Then the relay is energized through the relay driver transistor. The reset keys of the circuit are wired to set pins 6 and 8 of each IC. (Power-on-reset capacitor C1 has been added at BEP lab during testing as the state of output is indeterminate during switching on operation).
This electronic code lock electric circuit can be implemented in multiple security applications. We can set the circuit code lock in cars and make sure the car starts only when the correct code sequence is pressed via the key pad. This circuit is sure to boost the security system. It can be used in other multiple areas where security plays vital role.
PARTS LIST OF ELECTRONIC CODE LOCK CIRCUIT
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1 – R5 = 4.7 MΩR6 = 18 KΩ
R7 = 1 KΩ
|C1 = 100 nFC2 = 220 µF/25V|
C3 = 0.1 µF
|IC1, IC2 = CD4013T1 = bBC557|
D1 = 1N4001
LED1 = Any color LED
|RL1 = 12V, 150Ω SPDT relaySW1 – SW9 = Push to on switch key pad|