Unlocking windows 8 tablet using NFC ring
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If we could just graft a different antenna on the NFC Express module we would win at life!
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@johnyma22 said:
If we could just graft a different antenna on the NFC Express module we would win at life!
I did crack it open to see if this was possible but it was all integrated on a single board.
I will crack it open again and upload some pics, maybe somebody else with more engineering knowledge will see a way to do this. And since iv already spent the money on this, it will save someone else wasting their money if it wont work.
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You should be able to see the coil/antenna, probably around the outside of the circuit board. If you follow that to where the coil ends are there will probably be a pair of surface mount components there joining the coil to the rest of the circuitry.
You might be able to carefully de-solder these and then play around with adding a different smaller antenna at that point.
It is possible to kill the whole device if your antenna is poorly matched to the rest of the circuit though. -
@Lokki said:
You should be able to see the coil/antenna, probably around the outside of the circuit board. If you follow that to where the coil ends are there will probably be a pair of surface mount components there joining the coil to the rest of the circuitry.
You might be able to carefully de-solder these and then play around with adding a different smaller antenna at that point.
It is possible to kill the whole device if your antenna is poorly matched to the rest of the circuit though.@Lokki, @johnyma22 here are the pics, as you can see, its a single integrated board, I'm not sure you can add an antenna anywhere, but have a look and let me know. I do have a soldering iron, and although I'm not good at it, ill give it a shot !!
Top
Bottom
Top in case
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Ok, I've circled in red where the antenna connections to the radio are:
One possibility would be to carefully cut the tracks on the top before they get to the vias to go to the radio on the other side of the board, then connect a newer, smaller antenna at that point after scraping some of the protective lacquer off the remaining tracks. This should be reversible by re-joining the cut tracks later on.
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@Lokki, any recommendations on antenna ?
I did purchase the ACR122, Ill Pop that open to see what kind of antenna it has, but I'm guessing another circuit board. but to do this mod Will I need a loose antenna ?
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Yeah, you're most likely going to need to form your own antenna if you can't acquire one from somewhere. The "standard" 5 turns at ~50mm diameter coiled antenna might be interesting to try, refer to my sweet spot tester post that's here somewhere. If I get a moment I'll link it. I formed mine out of relatively thick transformer wrapping wire, that stuff is enamel coated so you don't get short circuits between loops.
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@Lokki said:
Yeah, you're most likely going to need to form your own antenna.
That's hard core uber geek !!!
ill give it a shot!!!
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Ah, here 'tis. For some reason I was looking for a picture. What I'm talking about is the horrid looking big test tag with the 5mm LED. Something like that connected to the board instead of a LED might be interesting to test.
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@Lokki said:
Ah, here 'tis. For some reason I was looking for a picture. What I'm talking about is the horrid looking big test tag with the 5mm LED. Something like that connected to the board instead of a LED might be interesting to test.
@Lokki, thanks for that, I get the idea of what I have to do now. so basically
1- I cut the antenna wires on the NFC express
2- I get some transformer wrapping wire.(is that like from a special electrical store like a dick smiths or any hardware store?)
3- I take 1 piece of wire, run it around 5 times to make a circle but try to make the circle have a 50mm diameter.
4- I solder both ends to where I cut the NFC express antenna offAnd then the magic happens ?
Cheers Jason
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If Dick Smith still sell useful electronic parts where you are... Jaycar/tandy(radio shack) or anything similar should do it. If you can't find proper wrapping wire you might get away with some solid core wire of a reasonably heavy gauge.
When you make your cut, try and leave a good amount of track on the top there from the vias for you to solder to, and bear in mind it's going to be delicate after the cutting, scraping and heat from soldering - so don't move your new antenna around too much once it's connected.Sounds like you've pretty much got the steps as they should be. Good luck, dude. Prepare to become a practitioner of the Dark Arts.
Actually, this project shows a 'normal' home made antenna for 125kHz. What you're doing with the wire is basically the same, just you're making yours smaller so that it couples with the ring better than a large antenna would.
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@Lokki good point, I will have to get to JayCar
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@Lokki so the guys at JayCar had no idea what i was talking about. they were trying to sell me normal copper wire. Instead I bought a pre wound inductor, I figure at least its probably the correct type of wire and I can just unwind it. and use it.
what do you think ?
Cheers
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yeah, that'd do it man.
I've been trying to find something I saw, where an inductor was used as an antenna. -
@Lokki said:
yeah, that'd do it man.
I've been trying to find something I saw, where an inductor was used as an antenna.so this is the coil with a 5 cm diamater, 5 turns.
basically I just solder this onto the spot you pointed out before. FYI, I wont cry if I kill it.
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yup, basically do that and have a play with it.
Possible results could include magic smoke release. But something should happen. Test it with a mifare card too, to see what goes on.You're gonna have to strip and tin that other end.
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just apply heat and solder for a little longer then usual before you try to connect it. You should see the enamel melt back and the wire take up solder.
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Once you verify whether it works or not you can start playing with different shapes and sizes for the coil. Have a look at @MrStein's thread with the nfc arduino for tips.
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@Lokki said:
just apply heat and solder for a little longer then usual before you try to connect it. You should see the enamel melt back and the wire take up solder.
you know last time I tried to solder a basic circuit board together it only ran for about a minute until a capacitor popped. Hopefully I do better this time. with it just being an aerial and all.
