digital combination lock!

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Related (http://cdn.instructables.com/FP4/X8WN/G4PBWWKS/FP4X8WNG4PBWWKS.LARGE.jpg) About This Instructable License: 27,141 views 33 favorites (/member/Nino123/) Nino123 (/member/Nino123/) Follow 7 digital (/tag/type-id/category-/keyw ord-digital/) combination (/tag/type-id/category-/keyw ord- combination/) lock (/tag/type-id/category-/keyw ord-lock/) cerradura (/tag/type-id/category-/keyw ord- cerradura/) electronics (/tag/type-id/category-/keyw ord- electronics/) electronica (/tag/type-id/category-/keyw ord- electronica/) passw ord (/tag/type-id/category-/keyw ord- passw ord/) contrasea (/tag/type-id/category-/keyw ord- contrasea/) Tags: COLORKEY (/id/COLORKEY/) by caromarcucci (/member/caromarcucci/) (/) let's make share what you make > (/about/submit.jsp) (/) Explore (/tag/type-id/) Create (/about/submit.jsp) Contests (/contest/) Community (/community/) Login (/you/)

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Page 1: Digital Combination Lock!

Related

(http://cdn.instructables.com/FP4/X8WN/G4PBWWKS/FP4X8WNG4PBWWKS.LARGE.jpg)

About This Instructable

License:27,141 views

33 favorites

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digital (/tag/type-id/category-/keyw ord-digital/)

combination (/tag/type-id/category-/keyw ord-

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electronics (/tag/type-id/category-/keyw ord-

electronics/)

electronica (/tag/type-id/category-/keyw ord-

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Page 2: Digital Combination Lock!

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.

See More (/tag/type-id/?q=)

(http://cdn.instructables.com/FBY/99SZ/G4PBWWKR/FBY99SZG4PBWWKR.LARGE.jpg)

How to Choose a Good

Password: A few quick

tips on how to stay safe

Electronic security code

lock system

(/id/Electronic-security-

code-lock-system/)

by arshad.pathanHow-To: Make an RGB

combination door lock

(/id/How-To-Make-an-

RGB-combination-door-

lock/)The Enigma Puzzle Box

(/id/The-Enigma-Puzzle-

Box/)

by TXTCLA55

(/member/TXTCLA55/)

Page 3: Digital Combination Lock!

Remove these ads by Signing Up (/account/gopro?

sourcea=removeads&nxtPgName=Digital+Combination+Lock%21&nxtPg=/id/Digital-Combination-Lock/?ALLSTEPS)

Step 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)

Step 2: Materials

(http://cdn.instructables.com/F9P/0SBE/G4PBWWLE/F9P0SBEG4PBWWLE.LARGE.jpg)

Page 4: Digital Combination Lock!

Here´s all that you will need.

NOTE: I took most of the materials from an old VCR board, so they were "free" making this

proyect really cheap. In total i spent about 13 dlls (most of the IC cost 76 cnts, exept for the D-

ff (about 1.15) cause i had no IC, but you can keep them for future proyects, they are a great

investment.

Components:

Lots of Diodes (about 20) to make one way connections.

One NPN transistor ( to feed the Relay Coil with enough current)

One Relay (to control the connected device)

One red LED ( to indicate when the system is LOCKED)

14 push buttons

Lots of resistors (doesnt really matter the resistance, its just to set the IC pins to 1 or

0[+ or -])

Two 7-segments Displays.

A Lot of wire!!

Integrated Circuits:

Two 7432(OR GATES) to build the DEC to BCD and the comparator

Two 7486(XOR GATES) soul of the comparator.

Two 7447 Display driver

(http://cdn.instructables.com/FZF/9DLG/G4PBSQAC/FZF9DLGG4PBSQAC.LARGE.jpg)

(http://cdn.instructables.com/FQ4/YDHD/G4PBSQAB/FQ4YDHDG4PBSQAB.LARGE.jpg)

Page 5: Digital Combination Lock!

Four 74175(4 D-FF) each is a memory able to hold 4 bits.

One 7476(2 JK-FF) for the display selector and to hold the OPEN CLOSE signal.

One 7404(NOT GATE) invert the clock pulsefor the display selector. ( you could use an

NPN transistor insted, cause you need only one gate ( the ic has 6).

Tools:

3 Protoboards (http://en.wikipedia.org/wiki/Breadboard

(http://en.wikipedia.org/wiki/Breadboard))Pliers

Exacto Knife

5V DC power supply(feeds circuits)

12V DC power supply(feeds the relay coil)

120V AC Power supply(feeds the device on the output)

NOTE:I used about 8 ft of wire, and advice about this, insted of buying expensive protoboard

wire, you could Buy 3 ft of ethernet cable, the strip it, and you will have 8 or 9 wires, each with

a diferent color and 3 ft long. (thats exactly what i do, since the normal protoboard wire is

about 10 ft per dollar.

But for a buck you could 3.3 ft of ethernet cable, so you would end up with about 27-30 ft!

Step 3: Dec to BCD

(http://cdn.instructables.com/FJM/DZ3X/G4PBSQAL/FJMDZ3XG4PBSQAL.LARGE.jpg)

Page 6: Digital Combination Lock!

The first step is building the input system, so you can comunicate with your lock.

I ve designed the following circuit in order to achive two main goals.

Turn any of the 10 numbers from (0-9) to its BCD (binary) counterpart.(Actually, there is

an IC for this purpose, but it wasnt in stock when i went to my local electronic shop., so

if you get it you will save yourself a lot of time and trouble, but I think is more fun this way

)

Being able to detect whenever a button is pressed.

To solve the first problem, we should take a look at this truth table to know which output

(ABCD) will be high (1) when we press each button.

D C B A] X

0 0 0 0] 0

0 0 0 1] 1

0 0 1 0] 2

0 0 1 1] 3

0 1 0 0] 4

0 1 0 1] 5

0 1 1 0] 6

0 1 1 1] 7

1 0 0 0] 8

1 0 0 1] 9

Now heres where something I love about Digitals comes to a use…

There are many ways of doing one thing…. Its just like maths, you can get to 3 adding 1+2, or

substracting 4-1, or 3 1….

In other words, you could build lots of diferents circuits to achive the same goal, this is

something that makes our current task easier.

I designed this circuit cause I thought it used few ICs, but you could design your own!

Now, I know some maybe scratching their heads trying to figure out why did I used so many

diodes, well here is the answer…

Diodes work like a one way connection, so in a pair connected as in my circuit, if there´s

(1) voltage on its "positive side" it will conduce current, so we will have voltage in the other

side aswell, but if there is a negative , or inexistent voltage (0) it will behave as an open circuit.

Lets check the behavior of these diodes, calling the first diode anode (+) "E", and the second

diode anode "F" and the output will be their connected cathode"X".

E F] X

0 0] 0

0 1] 1

(http://cdn.instructables.com/FOS/PWDB/G4PBSQAK/FOSPWDBG4PBSQAK.LARGE.jpg)

Page 7: Digital Combination Lock!

1 0] 1

1 1] 1

You can see we have the exact same behavior than an OR GATE, and then,Why

not using just diodes, that way you will save even more Integrated Circuits, and

money?...Well the answer is simple, and you should really take it in consideration,

the VOLTAGE DROPPED across EACH DIODE. It s normally about 0.65V. Why is

that? Because each diode needs at least 0.6 V across its anode and cathode to

make its junction get close, so it can start conducting.I

In other words, for each diode you connect and its working at the same time, you

will loose 0.65 V… that wouldnt be a big problem if we were only turning leds on,

but we are working with TTL IC, that means that we need at least more than 2 V.

And as we are starting with 5 v.. That means that conecting 5 diodes will cause a

failure in our circuit ( the integrated circuit wouldnt be able to distinguish between

0v and less than 2v…)

That´s why I never used more than 2 diodes in each input…

NOTE: You must connect a resistor connected to GND in each OR Gate input…

To solve the second problem I just added a diode to each ABCD, and 0, and connected them

together, so whenever any of those is 1, you will have a 1 on "Press"(P).

Now all that´s left is to build it on your breadboard, or if you want to save some more space

you can do as i did, and drill some holes in a construction paper and solder the diodes and

push buttons there...

If you need some more information about Logic Gates:

http://www.allaboutcircuits.com/vol_4/chpt_3/1.html

(http://www.allaboutcircuits.com/vol_4/chpt_3/1.html)

If you need some more information about diodes:

http://www.allaboutcircuits.com/vol_3/chpt_3/1.html

(http://www.allaboutcircuits.com/vol_3/chpt_3/1.html)

Step 4: Displays

(http://cdn.instructables.com/F3Z/BXK4/G4PBWWMX/F3ZBXK4G4PBWWMX.LARGE.jpg)

Page 8: Digital Combination Lock!

These step is one of the easiest, we just need to decode the ABCD inputs to drive the seven

segment display…And luckly there´s already an integrated circuit that will save us all the logic,

time and space.

If you are using a Common Anode display then you will need a 7447.

If you are using a Common Cathode display then you will need a 7448.

The wiring is the same, so either way you could use my schematic.

The inputs ABCD for each IC come from each memory´s output (we will review the memories in

the next step)

Step 5: Memory

(http://cdn.instructables.com/FJV/7O3V/G4PBWWMY/FJV7O3VG4PBWWMY.LARGE.jpg)

(http://cdn.instructables.com/FFA/2LXT/G4PBWWND/FFA2LXTG4PBWWND.LARGE.jpg)

Page 9: Digital Combination Lock!

This is were we change from combinational logic, to secuencial logic…

To make the 4 bits(ABCD) memory we just need a D- Flip Flop for each bit, and in the 74175

we have 4 of those.

Remember each number is represented in ABCD , so each 74175 can save one number.

For more information about how does the D-flipflop works, and how does it saves

information,:

http://en.wikipedia.org/wiki/D_flip_flop#D_flip-flop

(http://en.wikipedia.org/wiki/D_flip_flop#D_flip-flop)

The input of the first two memories (Data "D") comes from the DEC to BCD coder that we

built on the first step.

Well we have the information that each one is going to hold, but, when are they going to save

it?

Of course, one will save the first pressed number and the other the second pressed

number…

So, how do we get this effect? Well with another kind of FF (flip flop) the JK, when both J and

K inputs are high, it will change the state of the outputs to its complement (negation), in other

words, we will have on "Q" 1, then 0 then 1 again, then 0 and so on. This Q and Q´ are the

clock for the memories (what will tell´em when to save new data.)

The pulse that will determine when this change is made is the "P" that is high whenever you

press any number, but to save the information on time, we will need the opposite, so heres

where we use the NOT GATE.

In other words, once we push a button, the jk ff will change its output, turnin on the first

memory, so that it will save the data, then we push again and the first memory recording state

will be off, but the second memory will save the new data!

I added at this point a reset button that will turn both memories (ABCD) back to 0, and will

return the display selector (jk ff) to the first memory.

For more information about the JK FF:

http://en.wikipedia.org/wiki/D_flip_flop#JK_flip-flop

(http://cdn.instructables.com/FCQ/FDVN/G4PBWWNF/FCQFDVNG4PBWWNF.LARGE.jpg)

(http://cdn.instructables.com/FNT/S1N8/G4PBWWNE/FNTS1N8G4PBWWNE.LARGE.jpg)

(http://cdn.instructables.com/FZ9/2XOX/G4PBWWNC/FZ92XOXG4PBWWNC.LARGE.jpg)

Page 10: Digital Combination Lock!

(http://en.wikipedia.org/wiki/D_flip_flop#JK_flip-flop)

Now… why did i said we need four 74175?

Well to save the password!! While its possible just to set the password with resistors to GND

or Vcc, that will make your password static, and impossible to change if you get your lock

done in a PCB.

So, with a memory, you can save the password, and change it as many times as you wish.

The inputs will be the outputs of our displays memory, so when a positive pulse reaches their

clock, you will be coping whathever numbers are in the displays. (both, the memories and

password memories will have the same information). Of course the "new password" pulse

will only be avaliable if you already intruduced the correct password and opened the lock.

In all we will have a storage capacity of 2 Bytes or 16 bits!!

Step 6: Comparing

(http://cdn.instructables.com/FT2/TQLM/G4PBWWNX/FT2TQLMG4PBWWNX.LARGE.jpg)

(http://cdn.instructables.com/FYT/FRSE/G4PBWWNY/FYTFRSEG4PBWWNY.LARGE.jpg)

Page 11: Digital Combination Lock!

At this point we have a system thats capable of saving each number we press in one display

then the other, and copying that information to the password memories… we are still lacking

the essential, the Comparator… one circuit that will compare the two (ABCD) of the display

memories with the two (ABCD) of the password memories.. Again, theres already an IC from

the TTL family that does all the dirty job, but it wasnt in available in my local electronic shop.

So I built my own.

To understand how i did it lets look at the XOR truth table

A a] X

0 0] 0

0 1] 1

1 0] 1

1 1] 0

Notice that whenever A and a have the same value, the output is low (0).

So if they are diferent we will have a 1 at the output.

Meaning that with one XOR Gate you can compare 2 bits one of the display memory and the

other of the password memory. Based on that i built the following circuit, remember that you

can build it your own way, cause there are many ways to get to the same answer here in

digital electronics.

This circuit takes in the 8 bits of the display memories ( one bit per XOR, cause the other

input should be used with the password memory) and the 8 bits of the password memories (

its a 1 Byte comparator).

And will deliver only one output.

if and only if the information on both display memories is the same as the information in the

password memories, we will have a (0) low output. In other words, if the information on both

sets of memories differ, even on 1 bit, the output will be high (1).

Step 7: Open/Close

(http://cdn.instructables.com/F25/A96L/G4PBSQEY/F25A96LG4PBSQEY.LARGE.jpg)

Digital Combination Lock! by Nino123 (/member/Nino123/)

+ Collection I Made it!

Download (/id/Digital-Combination-Lock/?download=pdf) 7 Steps

Favorite

(/id/Digital-Combination-Lock/)

Page 12: Digital Combination Lock!

Finally the last part, we are almost done! Soon enogh you will be able to lock any device, or

electrify any fence,, ( Please dont!)

Now, we will take the last bit of information, and interrupt it with a push button, so if someone

accidentaly writes the correct password, the lock wont open.( i called this button "enter", really

clever, huh!,)

And after the enter button,will come the RS latch, one device that can turn Q´ to 1 if a there´s

a 0 on its R input, and save it, and Q to 1 if theres a 0 in the S input.

For more information on RS latch:

http://en.wikipedia.org/wiki/D_flip_flop#SR_flip-flops

(http://en.wikipedia.org/wiki/D_flip_flop#SR_flip-flops)

I connected "Q" to a red led meaning lock, or that the controlled device is OFF.

And "Q´" to a transistor that will provide the relay with enogh current to turn it, turning ON the

controled device.

"Q´" was connected to a push button, ( that i called new password button for obious reasons)

so that when you push that button it you will close the circuit between Q´ and the clock input

for the password memory. If Q´ is Low (system locked) nothing will change in the password

memory when the button is pressed, but if it is High (system Open) clock will be activated and

password memories will copy the information on the display memories.(changing the

password).

And connected a resistor to GND and to a push button (lock button) and from there to the S

input, so whenever you press it, you will lock the system.

Well, while i could have bought an RS flip flop just for this purpose, i still got one JK ff left from

my 7476.

And, cause the inputs R and S are asincronous, we dont need to worry about the clock. So

just wire things up as shown in the diagram ( as i did.)

(http://cdn.instructables.com/FFP/BQCN/G4PBSQEX/FFPBQCNG4PBSQEX.LARGE.jpg)

(http://cdn.instructables.com/FFX/QXIV/G4PBSQEV/FFXQXIVG4PBSQEV.LARGE.jpg)

(http://cdn.instructables.com/FU2/NFLO/G4PBSQEW/FU2NFLOG4PBSQEW.LARGE.jpg)

Page 13: Digital Combination Lock!

Make Comment

(/member/afz2004/)

1 year ago Reply (CHURV5KHFD1F37U)

(/member/Nino123/)

11 months ago Reply (CF4SYY8HH11IFHE)

(/member/afz2004/)

1 year ago Reply (CUNLWPBHF23QZ9G)

Be Carefull when you connect the relay to AC, use enough isolating tape.. You dont want a

short circuit when working with hundreds of volts!

After conecting everithing together…we are finally done!!! Please feel free to comment any

question or suggest, if you notice any problem or mistake dont doubt in ponting it out. Im here

to help.

Good lock, i mean, good luck with that lock.

afz2004 (/member/afz2004/)

nino, how to connect all this circuit? especially the display memories circuit. I don't

understand it with the internal memories. does it came together in display memories

circuit? thank you.

Nino123 (/member/Nino123/) (author) afz2004

Hey, sorry again for the late reply,

finals are killing me, but well thats

what you have to go through to be an

engineer! Well, about how to

connect it... Most of the diagrams Iposted, came from a software which

not only numbered each pin, but also

named it; in order to be able to

understan that, you need to know

your ICs, and by that I mean readingthe datasheet, and understanding

the basic operation of your IC, and

how to use each pin. I strongly

recommend, that you practice easier

circuits with each IC, just to get usedto the Pinout and the way they work,

and then youll be able to make any

bigger project using as many as you

need, after all, if you learn the

alphabet youll be able to writepoems, books or just about anything

after practicing, the same applies

here.

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 yourinputs (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

afz2004 (/member/afz2004/)

I'm sorry. actually I posted once only. Don't know how it repeated again. By the way,

thank you very much for your explanation. I will seek your advice if I stuck at

Page 14: Digital Combination Lock!

(/member/afz2004/)

1 year ago Reply (C5SPOVUHF23QZ9I)

(/member/azaki-1/)

1 year ago Reply (CBDTW37HEXSASTJ)

(/member/Nino123/)

1 year ago Reply (CKR3MRHHF243CDM)

(/member/azaki-

1/)

1 year ago Reply (CBTGA9CHEXSASTL)

(/member/Nino123/)

1 year ago Reply (CVHDA6HHF243CCY)

(/member/azaki-1/)

1 year ago Reply (C38EMNRHEXSASTF)

somewhere later. :D Thank you once again.

afz2004 (/member/afz2004/) afz2004

this is my new account from azaki-1. thank you.

azaki-1 (/member/azaki-1/)

hi. I have same project with you where I have to build digital combination lock. I just

want to confirm with you which is my project need to enter 4 numbers, and reconfirm

again the number input. If correct, then it will light up GO LED. if not, NOT GO LED.

So, it is my project almost same to you or not. Thank you in advance, and really need

your explanation on your projects.

Nino123 (/member/Nino123/) (author) azaki-1

I answered on the last comment reply,

but It has been a lot of time since the

last time I used Digital circuits, I can

totally tell you that using a Pic,

PICAXE, Arduino, Parallax, or anyother microcontroller would make your

whole proyect really easy. Its easier to

learn how to program (and maybe

cheaper) a microcontroller that

learning digitals. But if you, (like in mycase) MUST use Digital Circuits (TTL

74XXX) I hope my proyect serves as a

guide, If you really need more help, you

can send me a Personal Message, Ill

try to answer as soon as I can, just bepatient, Im an engineer student, I have

not a lot of free time.

azaki-1 (/member/azaki-1/)

hi. I have same project with you where I have to build digital combination lock. I just

want to confirm with you which is my project need to enter 4 numbers, and reconfirmagain the number input. If correct, then it will light up GO LED. if not, NOT GO LED.

So, it is my project almost same to you or not. Thank you in advance, and really need

your explanation on your projects.

Nino123 (/member/Nino123/) (author) azaki-1

Yes it really almost the same. On theoutput, the led that will go or will not go

out is just the same as my Relay for

110v, instead of wiring the relay to the

output, just connect the led directly

where the Q or Q' depending on yourcase. If you want it to be a 4 number

combination lock, youll have to add two

more displays, decoder(7447),

memory(74145) and comparation

blocks (7486). To make it doubleconfirmation, you can add another

flipflop (7476) before the led, so youll

need two "clocks" (correct number on

the input) for your last jk flipflop to turn

the Q' ON.

azaki-1 (/member/azaki-1/)

hi. I have same project with you where I have to build digital combination lock. I just

want to confirm with you which is my project need to enter 4 numbers, and reconfirm

again the number input. If correct, then it will light up GO LED. if not, NOT GO LED.

So, it is my project almost same to you or not. Thank you in advance, and really need

Page 15: Digital Combination Lock!

(/member/mark16/)

1 year ago Reply (CHYBU7YH742STQR)

(/member/djmudslide/)

3 years ago Reply (CV9R88DG9BWGBQ5)

(/member/Nino123/)

3 years ago Reply (C2JDLTZG9BWNS9Y)

(/member/mark16/)

1 year ago Reply (C6IKC11H742STQJ)

(/member/awsomehighvoltage/)

4 years ago Reply (CS6K09HG5KP9C49)

(/member/Nino123/)

4 years ago Reply (CU1QAYAG5KP7VQ0)

your explanation on your projects.

mark16 (/member/mark16/)

I also would like to ask if you can suggest a circuit with these functions: 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...

djmudslide (/member/djmudslide/)

hey amigo... he intentado tu circuito con un amigo, y tenemos multiples fallas! ...será

posible q envies algo de info extra a mi correo? [email protected]... sobre todolos mapas de conexiones, tengo dudas sobre los puentes q aparecen en el primer

mapa, y si existe una sustitucion de los diodos, o cual funcion cumplen (leí como un

OR)... gracias d ante mano!

Nino123 (/member/Nino123/) (author) djmudslide

listo amigo, revisa tu correo

electronico, te he enviado unarespuesta a tu comentario, si tienes

mas dudas, no dudes en contactarme,

suerte con el proyecto..

no he subido mas proyectos, por queactualmente estoy dedicandome a

aprender mas sobre

microcontroladores y PLC...

mark16 (/member/mark16/) Nino123

can i have a complete circuit connection of this project where all the circuits in

the step by step process are connected? i already made a simulation of this

circuit but it happened that there is nothing on the display i just wanna ask why

is that so... thanks

awsomehighvoltage (/member/awsomehighvoltage/)

why is there a white led there in the middle?

Nino123 (/member/Nino123/) (author) awsomehighvoltage

oh, that led!.. dont worry its notimportant at all...

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 toso i wont loose track of where the next

number will appear, but it doesnt affect

or improves the sistem

winzoque (/member/winzoque/) Nino123

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3 years ago Reply (CWG90FQGJQEHJDD)

hello to the creator of this digital combination lock i think that this project was

great...just want to ask something from your first step...i am having a problemwith the switch "9" ,why is it the number "9" switch is not working in me, it

keeps displaying number "8", so i want to ask if there is some problem with

your schematic diagram from your first step, your fifth diode from the top. the

one that is connected from the nineth switch connecting binary bit "A".

winzoque (/member/winzoque/)

hello to the creator of this digital combination lock i think that this project was

great...just want to ask something from your first step...i am having a problem with the

switch "9" ,why is it the number "9" switch is not working in me, it keeps displaying

number "8", so i want to ask if there is some problem with your schematic diagram

from your first step, your fifth diode from the top. the one that is connected from thenineth switch connecting binary bit "A".

Gopesh gopu (/member/Gopesh+gopu/)

ma chudayo tum

nikitasamsukha (/member/nikitasamsukha/)

nice

Uranio23 (/member/Uranio23/)

Hola que tal veo que este proyecto lo hiciste hace tiempo, tengo algunas dudas, me

estoy "inspirando" en tu circuito para hacer un proyecto de electronica, no nos dejan

usar micro ni nada de eso puras compuertas y cosas basicas.

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

EngineeringShock (/member/EngineeringShock/)

Nice

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. =)

Nino123 (/member/Nino123/) (author) EngineeringShock

yeah, i think that the best part of

building something like this

{designing everything from scratch} isthe excitment of the adventure...

having your first design problems,

having to do research to solve them,

{and probably go nuts for a few days

till you get it}... 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 couldnormally order online werent avaliable

around here, {thank to Steren, now

we got lots of IC and cool stuff

cheaper and faster than before}..

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4 years ago Reply (CUG3PVWG4PBX0H3)

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 singlechip...

but it was a nice first project...

now i look back at this, and feel a little

bit homesick, but proud to havelearned so much since then, and

willing to keep learning!

ps. thanks for the IC number :D

3nigmat1c (/member/3nigmat1c/)

It may or may not be interesting, but use of a CD74hc4511 chip will free up a lot ofboard space (it's a all in one 7-segment to bcd decoder with flip flop and latch). That

way you can support up to 7 displays with a chip per segment and a single 8-3

multiplexer. That can easily go from 7 to 15 with an additional multiplexer and only

need 4 lines for data (always), and 3 lines for addressing (1 extra per new

multiplexer).

Nice project, this was very similar to the Digital Systems final Project I had to do in

college.

AndrewGarza (/member/AndrewGarza/)

Impressive. I always wanted to make a clock out of low level logic like this. Justseems like a lot of work. It is amazing how much easier/cheaper using a micro

controller for something like this.

amando96 (/member/amando96/) AndrewGarza

indeed, arduino + keypad, + seven

segment displays and some code...

thats actually my next project, for aweather station.

HarveyH44 (/member/HarveyH44/)

Quite an impressive job, both the project and the write up. The only project I ever

attempted like that on a breadboard, was a digital clock, which kept terrible time. It

took months to wire up, and figure out what went wrong. I've since switched tomicrocontrollers. So much easier to debug code, and you can take it anywhere to

work on.

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 tolayout, and drilling so many holes...

Really nice work, though don't imagine very many people will build this, maybe a class

project.

Nino123 (/member/Nino123/) (author) HarveyH44

thanks, and yeah, i used this as my

final proyect in school, you see im

currently a 11th grade student here in

Acuña, Mexico(Cbtis 54! arriba

chivos bravos!)...

so I still dont know how to usemicrocontrollers (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

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4 years ago Reply (C4CZKV3G4PBOYEL)

beginner like me?, PIC, AUDRINO,AVR?...

ElmoRoyD (/member/ElmoRoyD/) Nino123

Saludos desde Monterrey, yo soy de

Sabinas y estudie en el CBTIS 20

hace ya rato. Es bueno ver gente dela región entrando a estas cosas

Nino123 (/member/Nino123/) (author) ElmoRoyD

claro que si amigo, yo tambien

estaba arto de ver muy pocos

trabajos echos por compañerosmexicanos, y pense "pues no keda

otra mas que poner manos a la obra"

y asi fue coomo empeze, ultimamente

he estado algo ocupado por eso no

he podido seguir pero prontocontinuare con los proyectos...

thatoneguydavid (/member/thatoneguydavid/) Nino123

i would suggest Cypress

Semiconductor PSoC -3

(programmable system on chip) with a

little practice writing C you canimplement really complex systems with

very few external components. they

take an FPGA and various analog

circuits and wrap them up with a

microprocessor on one chip.

drhoff (/member/drhoff/) Nino123

I agree with Luminous. Arduino is really great for beginners. If you can make

a project like this, then you will have no trouble with it at all. Great Instructible.

LuminousObject (/member/LuminousObject/) Nino123

For a beginner, I would definitely

suggest Arduino. You just plug it intothe computer and go. No need for any

fancy programmers or any of that. Just

a USB port and a cable.

peblairman (/member/peblairman/)

Great job! Not trying to flame it or anything, but it looks kinda like a bomb lol

Udon (/member/Udon/)

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.

Page 19: Digital Combination Lock!

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