hi all,
made my way to the forum when my local school asked me to come up with an idea for the school summer fete.
My idea is a crack the code stall,
using a keypad of sorts the as to input a four digit code with a green light coming on for each correct digit and a winners sound for all 4 correct ( could be three digit). I plan to tell them the first digit after an hour, then the second digit after another hour, and then the third so at the end of the fete someone WILL win. Needs to be recode able. I have no idea what I am doing so would need step by step instructions ( and I do mean step by step) cost also as to be very cheap ( as coming out of school kitty) Ideally if someone would like to take on this give me an idea of cost including delivery to Stockport near Manchester.

thanks here,s hoping the forum comes up trumps.

 

Why not just buy a cheap digital safe or make a box and put a combination lock on it or get a cheap briefcase with combination lock.

If you do want to build something I'm not clear how you see this working. Do I enter all four digits and then if one is correct the light comes on or does the light come on for each button press if correct? Also where is the incentive to be the first player, if I understand the rules I would be better to hang on until 2 or 3 digits have been guessed. If two digits of four are known there are only 100 combinations remaining which could probably be worked through in under two minutes. One way round this may be to have a button that randomly "guesses" one or two of the digits automatically, so the user the first player has a much chance as the last.

I would of thought you would be looking at £15 - £30 for the parts without programming, assembly, etc.

 

thanks for the quick reply,
I feel combination locks and bolts are too small and fiddly. hopfully the incentive will be the first opportunity to win the Prize (expected to be a donated ipad) and by making it progressively easier more incentive to stay to the end.
LETS SAY THE CODE IS 1 2 3 4
the player pays say 50p per go their guess is 1, 7, 9 and 2
a green light will come on and stay on for the 1 and a red light will come on for each of the the others, this is just an idea not set in stone just want more of a show presentation rather than slapping a brief case on the table.
Was thinking of a keypad door entry panel what do you think.

 

Yes, but it might be simplest if you could set this up with an Arduino....it can be done with transistors, but you're looking at 2 to 4 transistors per number. And it would be hard-coded.....with an Arduino/pic, you could change the password at will...

 

How much time do you have, weeks, months? If you have no experience in this you are going to find it hard and you seem to want something big and showy - lights, sounds, etc. which is going to cost. Like I said, just for basic parts, something like an Arduino Nano, standard LEDs, keypad, sounder, case, mountings hook-up wire etc. you are looking at £15-£30. You didn't say whether that was within budget.

 

I have got to 2nd week in July.
Would a keypad door entry do.
The budget is £20 but I think could go to £30.

 

A door entry keypad will do nothing on it's own. What sort of door entry keypad, do you have one in mind? You need to decide how you are going to convert key presses into red/green lights and as Mike33 suggests an Arduino may be the place to start. So Google "Arduino Keypad" and get some idea of what is involved.

 

well might need to simplify for the first summer fete.
was thinking a door entry would light a green led when correct code selected

 

OK, just taking a step back, I guess you could just do it with push buttons and a patch-panel/breadboard. To set the code you would just use wires to patch the switches into the the LEDs. This would mean that the LED would come on as soon as the user pressed the button, but it would be possible to have a latch so that the LED stayed on after the button was pressed until, say a "clear" button was pressed.

Thinking about it if you put a 4 pole switch between the latches and the LEDs they would only come on when the 4 pole switch is pressed.

 

How much experience do you have with electronics?

If you were provided with a schematic, could you build the circuit on a breadboard? Could you then figure out how to wire and solder it to a generic PCB (stripboard)?

If yes, then you could use a PICAXE microcontroller with a 12-button keypad, an LED (or several) and perhaps a buzzer and/or lighted fan if you really want to get people's attention - all within your budget I believe.

Yes, this would require programming, but this is a simple enough project that I could write the code for you, post it here, and you could simply download it into the microcontroller.

You could punch a specific code into the keypad to get to allow you to change the player's code on the fly. We could light up four LED's, one per correct digit of the four-digit player code, then a fifth and a buzzer/fan to indicate a winner. These four LEDs could either be set to light up as the player pushes the correct button or on a timed sequence (the latter being a little more difficult). Alternately, you could punch in another code to manually eliminate the need for the 1st, 2nd, and 3rd digits (and light up corresponding LED's) as you saw fit depending on how the fete was going. Or use switches only you have access to to eliminate digits 1-3.

Just a thought.

 

OK, I've sketched up the latch idea images attached. I'm not saying this will work as is because I haven't tested it but it gives the idea. 4 of the 1-9 switches would be connected to "SWITCH_TERM" with flying leads, this would set the code. The player enters the code and presses "Enter", the correct presses would be indicated by Green LEDs, the Red LEDs are just connected to inverters so they are on if the green are off and off if the green are on.

I'm sure this can be improved and suggestions welcome but you could build the whole thing on a breadboard and the bits (11 push buttons, 4043, 74HC14N, 220Ω resistors, red/green LEDs) can be bought from http://cpc.co.uk or elsewhere. I'm assuming you will run it off batteries, 3x1.5V would give you 4.5V which should be OK.

 

My experience is nil nearest to this I have built is a buzz wire game which didn't even involve a pcb.
I am asking around my friends for anyone who could work from a schematic.

 

Or this keypad might do it - http://cpc.farnell.com/eao/eco12150-06/keypad-12way-matrix/dp/SW04507
instead of individual switches, although there are no connection details on there so it's hard to tell
http://cpc.farnell.com/eao/eco12150-06/keypad-12way-matrix/dp/SW04507

 

Another suggestion from off the forum was use a old electronic mastermind game just rebox it, but with that I don,t know the code from the start and it changes after ten goes.

Oh can I just thank you for the time and effort but it is looking beyond me so far.

 

Found this on you tube

http://m.youtube.com/#/watch?v=pYyQfFyrrY8

 

That link just takes me to the youtube home page

 

I found it by typing in the end of the link into the Youtube search. Here it is.

OP, this is a microcontroller circuit. This is what I was describing in my last post. I wasn't planning on including an LCD only because it would add 6-9 pounds to the budget, but it could be done.

I could draw something up showing you where to cut traces on a stripboard to make your own PCB, but you'll have to be able to solder. Is this something you can do?

I'd be happy to put the circuit together and have you pay for parts and shipping alone, but since I'm in the U.S., it would cost over 15 pounds to ship, almost half your budget.

I there is someone else in the U.K. who wants to build this and work out a deal with the OP, I'll write a program and draw up a schematic for you to work from. The PICAXE is based in the U.K., so sourcing all the parts should be straightforward.

 

I do own a soldering iron but think might be a bit on the heavy side for a pcb
and have only used it once before.
and I can't read a schematic drawing honestly thought it would be easier than this.

 

ok been told from a friend of someone who might be able to build it from a drawing i get of, ( I see him Tuesday) and he will probably charge me so dependent on his confidence in making it and his fee might take you up on your offer elec mech.

 

Take a look at this post and show it to your buddy. It shows the front and back of a strip board, where to make cuts to break traces, and where to solder components. It also shows a schematic. The one shown is far more complicated than the circuit you will need, but it will give your buddy an idea of how much work is involved. If I do the stripboard design, this shouldn't require too much time from your friend and hopefully cost you less in the end.