I won't kid you - these two cards need some serious construction skills, and are both experimental (particularly the dialler), so are no beginners projects, but wait 'til you see the face of the first person you give one of these to! Don't try these designs unless you have successfully made a few electronic items before - they need good soldering skills, and ideally a way of making some printed circuit boards, although if you soldering skills are REALLY good, and you are making just a few, it is possible to make versions of both of these cards without circuit boards, and just "point to point" wiring - my prototypes were done like this.
Firstly the torch. This is the easier of the two. Although you could use some PVC cards to enclose a hand-wired version (keep reading on to see this technique used in the "dialler"), making copies is much easier with a proper PCB. A tutorial on how to make a PCB is beyond the scope of this article, but if you haven't tried it before, it is a really good technique to be able to do and opens up a countless variety of electronic projects. Here is an instructable on a simple toner transfer PCB - personally I find more repeatable and professional results with the photographic method - couldn't find an instructable for this one, but there is plenty of info on the web - I use a very cheap 500 W halogen light from the local hardware store to expose mine for a few minutes, and then develop, etch and tin. If there is enough demand, I might get some universal "torch" and "dialler" boards commercially made.
Anyway, assuming you can get a PCB made up, the file which I used is included below - this can be modified on a standard graphics package. If you can't read EPS files, then try the 300 dpi bitmapped version included below as well. You can of course use a specialised PCB package, but I wanted an unusual cursive font on mine, so just hand-drew the design on a graphics package. This allowed me to incorporate my name into the actual circuit board - the electric current actually goes though my name! If you want to produce a reasonable batch, you will probably want to tile your image over the page after you have made your changes.
Here you can see the parts - a PCB, coin cell (CR2032), a coin cell holder, a 3 mm LED (any colour should be fine), a PCB-mount switch, and a resistor. A complete parts list for both projects is available as a link below if you want to find where to source some of these components. The value of the resistor is usually around 68 ohm for most colour LEDs. It is a surface mount device, so is very small - the exact type you get isn't critical - I used a "1206" package as it is easier to solder, but 0805 or 0603 packages can be soldered on as well if you have good eyesight! If you are using a blue or white LED, they are meant to be too high-voltage to really use with a single coin cell, but if you use a bright one, you can just remove the resistor completely (short with a blob of solder or use a "0 ohm resistor") and the light, although not full intensity, should be quite bright (see the image of it turned on a couple of pages later). You want to get the highest intensity 3mm LED you can find - there are some great deals on ebay, which is usually the cheapest place to find these.
Business Card Parts List.pdf
Business Card Tech Notes.pdf
If you want more information on how both of these projects work technically, including how to properly choose resistor values, see the extra technical information sheet that I have posted below as well. I could make up a batch of 100 of these for under $1 each, including PCB -not bad for some extreme marketing, but you could probably even half this price if you were serious about making these in quantity and could do without the battery holder (see the notes in the parts list about welding batteries).
I'm afraid a complete tutorial on soldering isn't within the scope of this instructable either, but the torch is quite easy to solder. I put a blob of solder on the iron, and then whilst holding one end of the component down with my finger or some tweezers, I apply this blob to one end of the component. Then I solder the other end, and finally go back to the first end and solder it again. All components can be put either way around except for the LED - for this one the longer lead is the positive (check before you shorten it!), and should be at the bottom of the PCB in this image (next to the resistor). The negative end can also usually be told by looking for a flat mark on one side of the LED's plastic cover.
Insert the battery with the positive side up, and press the button, and you should have a functioning key ring light! As I mentioned, this design is an experimental prototype only - if I produced these on mass, I would probably change a few things. Firstly, I would make the board smaller still (for cost), and put the name/contact details on the reverse of the board. I might also change the CR2032 cell to a CR2016 as this is thinner, and cut a hole in the board to mount it inline. This would make the whole thing very thin indeed. I might even encapsulate the board in clear heat shrink tubing or the like, to stop it shorting out on keys whilst in the pocket.
Do you think that you can handle an even more advanced design? If so, read on to see how the "autodialing card" works ...
