Got space enough to wrap a proper coil around your finger
This project was created on 03/16/2014 and last updated 6 months ago.
For all those who aren't antenna engineers, the article at this link gives you a good basic introduction on how things work. To pascalmuller - you make me smile :) Hope this is informative for you. http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf
What I found out is that the antenna is not a true antenna, but an induction coil. I do not really have a background in electronics, but as far as I understood there is a minimum size for the coil, but bigger is better.
The problem I had was related to the solder connection. The copper wire in my keyfob had some sort of coating. When I shortened the wire and resoldered, the connection was apparently bad. I heated the end of the wire with a lighter and then tinned it with solder, before soldering it onto the chip. I repeated this two times with success.
What I did note, is that the ring works better when scanned horizontally (flat) than vertically. I'm not sure if this is related to the polarization of the magnetic field or not. This might explain why the NFC inlays of the Kickstarter project are oriented differently.
So, I got all excited and went to make one... and apparently antenna design is a really complicated field for a good reason. So, how did you go about transferring the antenna over onto the ring exactly? Does the amount of turns matter? Does the length of the wire in the antenna? Does the diameter of the coil? Is the wire allowed to touch itself in the coil(when unwinding it seems to be coated, not sure if for shape or to insulate also)? First attempt I did everything in a bit of a rush, rewinding the coil a little sloppily(but it was the same length of wire). Second attempt I did everything super carefully but cut out about a .5cm of wire from the antenna. Third attempt I am just trying to unwind the antenna and then rewind it back to make the chip work again and failing. Any help please?