Hardware-Based Keypad Lock

    Here is a six-digit keypad lock I made that is completely implemented in hardware (no programming). If you like this project please vote for it in the Epilog Challenge.
Theory of operation:
     You set the code with the headers you see at the bottom left of the board in the picture. If you hit a wrong button, the part of the code you have entered correct so far will be reset. If you mess up a certain amount of times the keypad will lock and can only be unlocked by pressing the button you see at the bottom right corner of the large board. The count of how many times the code has been entered incorrectly is reset once you enter the correct code. Each time you press the correct button the corresponding red LED will light.
Things I would like to improve:
    The only thing I would like to change about this lock is to make it so that you can't enter the code in any order. For example, as the circuit is now, if the code was 2, 1 you could also enter it as 1, 2.
Further Notes:
   I had to substitute some components that I did not have for others. For example, instead of an AND gate, I used a NAND gate in conjunction with a NOT gate at its output.

Step 1 Parts/Tools List

Parts:
(3) 74HC74
(1) CD4017
(2) Triple three input NAND gate ICs + (1) 74HC04 hex inverter OR (2) triple three input AND gates such as the 74HC11
(1) 74HC04 hex inverter
(1) 74HC30 8-input NAND gate
(2) CD4077 quad 2 input XNOR gate
(6) 555 timers
(6) 100μF electrolytic capacitors
(6) 0.01μF ceramic capacitors
(6) 1K ohm resistors
(6) 2n2907 PNP transistors
(16) 2n2222 NPN transistors
(1) 5V SPDT relay
(1) 1N4001 diode
(36) 10K ohm resistors
(7) 100K ohm resistors
(7) 470 ohm resistors
(7) Momentary push button switches
(6) Red LEDs
(1) White LED
(2) 6 pin male headers
5V power source such as a cell phone charger
Perfboard
Various colors of wire
Tools:
Soldering iron
Rosin core solder
(optional) Desoldering iron

Comments

[RITESH KAKKAR]

nice work man.....................

[rtty21]

I love this. Your schematic is AWESOME!!!!!!!!

[bogdanfirst]

Your design is much much too complicated. There is a simple design that comes from an Elektor magazine(i think) that uses just a counter and a transistor. I've built it when i was a kid.
I've found some schmeatics here: http://www.scribd.com/doc/51140395/Simple-ic-projects under 'security door key 1'.

[trumpkin]

Great circuit! Thanks for sharing. However, I believe that circuit would be especially easy to hack as all you would need to unlock it would be a positive wire with a common ground to the lock. Then you just tap the positive wire on one of the connections to one of the buttons and you could unlock it. That being said, I'm willing to admit that my circuit may be over-complicated. Also, I never meant my project to be a "practical" lock.

[mwagner63]

how do you program the code in the lock. also its cool and all but does it just turn on an led cause if it does why not just hook an led to a switch and hide it somewhere. hmmmm

[trumpkin]

You set the code by putting jumpers on the double row header. Obviously, you could hook this up to a device to lock a door or something (your not limited to the LED).