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Wow wouldn't it be cool to build yourself an electronic lock to protect your costly things? Yes we bring you the Simple Code Lock kit which is basically an electronic code lock that responds only to the right sequence of four digits that can be punched in through the nine keys available on a typical keypad. If an incorrect key is pressed, the lock gets automatically reset. This circuit can be usefully employed in cars so that the car can start only when the correct code sequence is keyed in via the key pad. The circuit can also be used in various other applications. No. of ICs used: 2
Things Which you can Learn:
*Application of the Dual D Flip-Flop IC CD4013 for logic conversion.
*Application of transistors for switching purposes.
Enter into the Sci Fi world and build yourself an exciting Code lock based on the concept of D latch and amaze your friends
The circuit of the Simple Code Lock is built around two CD4013 Dual-D Flip-Flop ICs. The clock pins of the four flip-flops are connected to a, b, c and d pads in the circuit. The correct code sequence for energisation of relay (RL1) is realised by clocking points a, b, c, and d (in that order). The five remaining switches are connected to the reset pad which resets all the flip-flops. Touching the key pad switch a/b/c/d briefly pulls the clock input pin high and the state of flip-flop is altered.
The Q output pin of each flip-flop is wired to D input pin of the next flip-flop while D pin of the first flip-flop is grounded. Thus, if correct clocking sequence is followed then low level appears at Q2 output of IC2 which energises the relay through relay driver PNP transistor BC557 (T1). The reset keys are wired to set pins 6 and 8 of each IC. A Power-on-reset capacitor (C1) is also connected as the state of Q output is indeterminate during switch ON operation.