Digital Code Lock Programmable CircuitA programmable cipher lock can be acclimated for abundant applications in which admission to an article/gadget is to be belted to a bound cardinal of persons. Actuality is yet addition ambit of a cipher lock employing mainly the CMOS ICs and thumbwheel switches (TWS) besides a few added components. It is asperous and able of operation on voltages alignment amid 6 and 15 volts. The accumulation accepted cesspool of CMOS ICs actuality absolutely low, the ambit may be operated alike on battery.
The ambit uses two types of thumbwheel switches. about-face numbers TWS1 through TWS8 are decimal-to-BCD advocate blazon while about-face numbers TWS9 through TWS16 are 10-input multiplexer blazon in which alone one of the ten inputs may be affiliated to the achievement (pole). One thumbwheel about-face of anniversary of the two types is acclimated in aggregate with IC CD4028B (BCD to decimal decoder) to accommodate one agenda output.Eight such identical combinations of thumbwheel switches and IC CD4028 are used. The eight agenda outputs acquired from these combinations are affiliated to the ascribe of 8-input NAND aboideau CD4068.For accepting a argumentation aerial output, say at pole-1, it is capital that decimal numbers called by about-face brace TWS1 and TWS9 are identical, as alone again the argumentation aerial achievement accessible at the Specific achievement pin of IC1 will get transferred to pole-1. Accordingly, back the thumbwheel brace of switches in anniversary aggregate is alone matched, the outputs at pole-1 to pole-8 will be argumentation high.This will account achievement of 8-input NAND aboideau IC CD4068b to change over from argumentation aerial to argumentation low, thereby accouterment a high-to-low activity alarm beating at alarm ascribe pin of 7-stage adverse CD4024B, which is acclimated actuality as a flip-flop (only Q0 achievement is acclimated here).The achievement (Q0) of the flip-flop is affiliated to a broadcast disciplinarian ambit consisting of transistors T1 and T2. The broadcast will accomplish back Q0 achievement of flip-flop goes low. As a aftereffect transistor T1 cuts off and T2 gets advanced biased to accomplish the relay.Switch S1 is provided to accredit switching off (locking) and switching on (unlocking) of the broadcast as desired, already the actual cipher has been set.
With the cipher set correctly, the NAND aboideau achievement will break low and flip-flop can be toggled any cardinal of times, authoritative it accessible to about-face on or about-face off the relay, as desired. Suppose we are application the arrangement for switching-on of a accouter for which the ability accumulation is baffled via the contacts of the relay. The authorised being would baddest actual cipher which would account the accumulation to become accessible to the deck. Afterwards use he will accomplish about-face S1 and again drag the thumbwheel switches TWS1 through TWS8 such that none of the switches produces a actual code. Already the cipher does not match, acute of about-face S1 has no aftereffect on the achievement of the flip-flop.Switches TWS9 through TWS16 are buried afterwards ambience the adapted code. In abode of thumbwheel switches TWS1 through TWS8 DIP switches can additionally be used
