I've always wondered how did electronic locks work, so once i finished the basic digital electronics course I decided to build one myself. And I´ll help you to build your own!
You could connect it to anything from 1v to 400v(or maybe more that depends on the RELAY), DC or AC, so you could use it to control another circuit, or even to electrify a fence!! (please dont try that, really dangerous)… I connected a mini chrismas tree to the output (110v) cause I hadnt taken the holydays decoration off my lab, so it was around at the time i finished the proyect.
Here are some pictures of the finished System, and a video too, so you can see it working.
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Signing UpStep 1: How does it work?
First I thought in what was needed to be processed and how. So i drew this diagram as a map to guide me as i build each part of the proyect. Heres a summary of how it works.
- First we need a circuit to decode the 10 possible inputs (0-9) to its 4 output BCD (Binary Coded Decimal), and another output that tells us when any button is pressed.
- Then we need to build the circuit for our two 7-segments displays to work properly, with 4 inputs for a BCD number and of course 7 outs for our displays, ( I used the IC 74LS47)
- Then a circuit to save each pressed number and toggle between displays
- As well as an internal memory for our password
- And, the hearth of our lock, the comparator (its 8 bits ´cause there are 4 bits per digit in the display, meaning that if you want to do a 4 digit lock you will need two of this connected together.) This will tell us if the numbers in the displays are the same as the password saved in the internal memories.
- And finally a circuit to keep the OPEN or CLOSE signal for an undetermined time, and of course an output (thats whatever you want to control with your lock)
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The 74175 is just as any other TTL IC, you have to power it with 5v, ground, and in this case, youll have to give it a signal that will trigger the change of state on the outputs(which will remain on that state indeterminately), acording to your inputs (which youll control on the keypad) . In this case, the output are coded to BCD, and then translated from that to a 7segment display "language" by our 7447
Code Breaker
Three digit code (0-9)
Three LEDs for right number but wrong position (red)
Three LEDs for right number and wrong position (green)
One digit display for the number of tries
One increment button for each digit
One GUESS button
One STORE button for new code
Switch debouncing using 555 timers or one shot multivibrators
Master reset button
thank you very much i would really appreciate it if you would respond with this post...
no he subido mas proyectos, por que actualmente estoy dedicandome a aprender mas sobre microcontroladores y PLC...
I just connected it in the same spot as the first display clock, so i can always know wich is the next digit, (the first or second display), its just a visual aid to so i wont loose track of where the next number will appear, but it doesnt affect or improves the sistem
Me preguntaba si podrias darme mas info sobre el circuito, mi problema esta a la hora de querer hacerlo de 4 numeros la clave, no se como cambiar de memoria cada que pulso un boton... Tu lo haces con el J-K pero como seria para 4 ?
Gracias y espero que puedas responder
The LS7220 or LS7222 chips are designed so that you can do the majority of this, minus the displays. I remember when I did this project from scratch. I designed it very similarily.
=)
as i mentioned around the begining, i was trying to use the most basic logic posible, you know, it was when i just completed my first digital electronics course, and most of the IC you could normally order online werent avaliable around here, {thank to Steren, now we got lots of IC and cool stuff cheaper and faster than before}..
anyway, i built it so much time ago... and now i perfectly know how to use uControllers, {PICs}.. so, everything could be controlled from a single chip...
but it was a nice first project...
now i look back at this, and feel a little bit homesick, but proud to have learned so much since then, and willing to keep learning!
ps. thanks for the IC number :D
Nice project, this was very similar to the Digital Systems final Project I had to do in college.
thats actually my next project, for a weather station.
Might also look into making PCB at home. It's not very expensive, and pretty easy with a laser printer. Although, got a hunch your project would still take sometime to layout, and drilling so many holes...
Really nice work, though don't imagine very many people will build this, maybe a class project.
so I still dont know how to use microcontrollers (will be seen on 12th), so I used everything i knew so far.
And yeah, microcontroller look really cool, so cant wait to try them!!
which one will be the best for a beginner like me?, PIC, AUDRINO, AVR?...
This is really good! It's a lot of info to put together.
I'm starting a Digital Electronics course in Feb. so I'd love to try build this.