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NFC ring to unlock Android

Got space enough to wrap a proper coil around your finger

This project was created on 03/16/2014 and last updated 9 months ago.

Description
There is the great NFC LockScreenOff Enabler to easily unlock your phone. But it does only make sense to me when I wear the corresponding tag on me.
Balancing my phone in the left hand makes it easy to unlock, when you wear a ring on that hand (same for the right hand of coures). While waiting for my ring from the Kickstarter campagne I made my own:

- Take apart a NFC keyfob, remove the coil and unsolder the chip.
- Find a tube and add layers of tape to match your ring size, use grease underneath the tape for easy removal of the tube lateron (I broke my first ring removing the tube)
- add a layer of glass or carbon fabric for reinforcement
- wind the wire around the assembly, glue the chip on top of it and resolder
- use plastic around as a cast and fill with polyester or better epoxy
- cut, grind, remove tube and tape and polish!

Watch the short video ("Unlocking w NFC" youtube link): the ring works really smoothly with my i9505.
Discussions

DrIce wrote 5 months ago null point

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

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pascalmuller wrote 7 months ago null point

I'm also failing: after unwinding the antenna and rewinding it, it fails to work.

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pascalmuller wrote 7 months ago null point

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.

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nurturingFog wrote 8 months ago null point

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?

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joe.h.faber wrote 9 months ago null point

Simple keyfob off ebay- split it with a knife

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Eric Evenchick wrote 9 months ago null point

Nice, you beat the kickstarter to production! I also think this one has a more unique look to it.

I'm curious what NFC keyfob you used to do this... was it easy to disassemble?

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