What you need

Step 2: What you need

One CR2032 battery (I got them for about 16 cents on ebay when I bought 100)
One CR2032 battery holder (I used part 18-3780 from www.rapidonline.com. This costs around 14 cents in quantities of 100 - these are a common type of holder that you should be able to find at places like www.mouser.com if you are on the other side of the Atlantic to me!)
One PIC16F57 (Order code 1556188 from www.farnell.com - These cost 66 cents each in 100+ quantities - again, you can find them at www.mouser.com)
Four surface mount switches (Part 78-1130 from www.rapidonline.com at 20 cents each)
Some miscellaneous resistors and capacitors in an "0805" surface-mount package - you will need 5x100 ohm resistors, 2x10k resistors, 1x47k resistor, 1x47p capacitor, and 1x100n capacitor - any of the suppliers mentioned above do these, and they cost almost nothing!
75x "0603" LEDS - as bright as possible, and as cheap as possible! I used item 72-8742 at 6 cents each from Rapid, but again, you should be able to get them at other suppliers. In quantity, you can get these down to about 3 cents each.
Some double-sided foam adhesive tape that is slightly thicker than the battery you are using - mine was 4.5mm thick)
A printed circuit board (PCB) for the project - instructions for producing your own are beyond the scope of this article, but you may have some success with the iron-on or photographic technique (my preferred technique). You can find instructions for making your own printed circuit boards elsewhere on instructables and other sites. The PCB layout is reproduced below in a PDF file if you want to try yourself.

You will also need a soldering iron (plus solder), a cutting knife, some spray adhesive, and a way of printing the front of your card - you can use a colour laser or inkjet. I printed on OHP transparency film. You will also need a way of programming the PIC microcontroller. I use the PICKit2 which is part number 579-PG164120 from www.mouser.com, and available at around $35. A strip of 5x0.1 inch PCB pins (such as 22-0510 from Rapid) can be pushed into the programmer to act as an interface with the board.

MatrixPCB.pdf(595x842) 17 KB

MatrixPCBMirrored.pdf(595x842) 17 KB

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MatthewEnderle says: Aug 14, 2011. 7:28 PM

got an idea tom to revise the board. Where the Battery is placed cut out a hole and place the battery in the hole, and use tin flaps soldered to the board. That will make it thinner.

glocketz says: Apr 4, 2009. 2:37 PM

Hey, Sunstone circuits (custom pcb manufacturer) requires the matrix to be in either a .RAR, .123, . BRD, or .BIN formats. Can you please upload a copy of the matrix in one of those formats so I can have a circuit printed? Thanks.

tomward (author) in reply to glocketzApr 5, 2009. 1:18 AM

I have loaded an Eagle .BRD file on the last step of the instructable, but it is slightly different - see the comments on the last page.

l4a in reply to tomwardApr 14, 2010. 1:09 AM

Hello, I have a bit of a problem. And I'm asking for a help. I have succesfully soldered everything and programmed it. But it doesn't work as it should. When I insert the battery all the LED's are turned on. Even if I press one of the four switches nothing happens (all the LED's are still on). Could you help me with the problem, please? Thanks

tomward (author) in reply to l4aApr 14, 2010. 10:03 AM

Hi - sorry, but it is pretty near impossible to troubleshoot remotely without access to the circuit. My best guess is that the program is not running at all - perhaps due to an incorrectly programemd fuse/option bit.

l4a in reply to tomwardApr 19, 2010. 6:59 AM

Hi again. I'm new in this and I'm having some troubles understanding your solution. Could you please tell me where can I select this fuse/option bit?
Thank you for your time! I really appreciate it.

tomward (author) in reply to l4aApr 21, 2010. 12:17 AM

Looking at the source code again it looks like I put the fuse options into the source code in the first few lines so that shouldn't be a problem. I would suggest programming my original hex file (from the the zip) - if this works then it is a change you made to the code that stopped it working. If it doesn't then things get harder to work out and it must be in the hardware. Let us know how you get on.

l4a in reply to tomwardMay 4, 2010. 9:24 AM

Well I haven't been able to fix it so I decided ti make another one. And even this one doesn't work. I have checked all the connections and everything seems OK. So is it possible that I have overheated the PIC while soldering?

p.s. Is it possible that you could send me one of your prototypes? I would pay you of course.

Thanks

tomward (author) in reply to l4aMay 4, 2010. 10:48 AM

Hi - really sorry, but only ever made one and this disappeared somewhere when being shown at a maker faire in the US. Are they programming/verifying OK? If so then you prob haven't blown up the chip - I think that they are less sensitive these days to heat/static etc than they used to be. Send me a private message with your email address and I will try to help if I can.

l4a in reply to tomwardMay 5, 2010. 11:02 AM

I think I might have solved the problem. I don't know how I did that but I turned the LEDs up side down! This week I'll try to do another one and I'll tell you the result!