Step 4: Does it Work?

Picture of Does it Work?
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 ...