My payment card was just a bit too wide to fit in my cellphone’s cover. The phone’s own NFC antenna is at the top - and I use it all the time - so the card had to be at the bottom of the cover to avoid triggering the phone all the time, in portrait orientation so-to-speak.
So I dissolved the card in acetone to extract the NFC chip and its antenna, then carefully reshaped one end of the antenna so it’s a bit less wide (and since I couldn’t modify the length of the wire or the number of turns in any way to avoid de-tuning the antenna too much, I sort of accordioned one side of the rectangle to accommodate the extra length of wire).
Then I set the new shape of the antenna permanently by carefully applying a piece of packing tape over it, flipped it over, taped over the other side to seal everything, then carefully cut around the new, ultra-thin, stubbier contactless payment “card”.
Amazing, I have never thought of that! I have always carried my card behind the phone, which is a bit too thick for my liking, but this is such a great idea, thanks for sharing!
I dissolved the card in acetone to extract the NFC chip and its antenna,
Wouldn’t the acetone also dissolve the insulation around the antenna wire? So when it touches itself, it shorts itself out, and – electrically speaking – you only have one turn of thicker wire?
Wire that thin is usually insulated with an enamel coating. I’d guess it’s either unaffected by acetone, or just tougher to breakdown. Allow the card to dissolve, but remove and dry asap, don’t let it linger longer than necessary.
My guess is it wouldn’t work. On a magnetic antenna, the number of turns don’t affect range, but they do affect the frequency to which the antenna is tuned. It needs to be tuned roughly to the frequency the protocol operates on, otherwise it won’t work.
In addition to that, these antennas also need to pick up power, which is also relative to the number of turns.
Seems like something to experiment with at some point. I do have access to test contactless card readers but not sure how they would feel about me destroying the test cards.
Well if it dissolved any insulation, it will not work, as the coil isnt even coiling. It is not a one big coil buy just two ends shorted(or as in the picture, a very small coil. Since this works i can only conclude coating does not dissolve in acetone
I’ll do one better:
My payment card was just a bit too wide to fit in my cellphone’s cover. The phone’s own NFC antenna is at the top - and I use it all the time - so the card had to be at the bottom of the cover to avoid triggering the phone all the time, in portrait orientation so-to-speak.
So I dissolved the card in acetone to extract the NFC chip and its antenna, then carefully reshaped one end of the antenna so it’s a bit less wide (and since I couldn’t modify the length of the wire or the number of turns in any way to avoid de-tuning the antenna too much, I sort of accordioned one side of the rectangle to accommodate the extra length of wire).
Then I set the new shape of the antenna permanently by carefully applying a piece of packing tape over it, flipped it over, taped over the other side to seal everything, then carefully cut around the new, ultra-thin, stubbier contactless payment “card”.
Now it fits really smartly in my cellphone cover!
Kudos for the effort. With that said, this would definitely raise some eyebrows if you have to return the card when getting a new one.
I’ve never had to do that… Just say you lost it.
I just wanted to say your dad is definitely proud of you dude
>ExtremeDullard
>most interesting post
???
You just had to 1-up everyone here…
You clever, I like.
I am surprised that no one sells cases designed for exactly this
You are fucking crazy. I love you.
Next time someone calls me a maniac, I’ll show them this.
Definitely doesn’t live up to their username.
The fact it’s secured with a piece of sellotape is just *chef’s kiss*.
Well, what if you need an actual card for identification in the bank or something similar? Do you just show them the dissolved one?
Don’t know about OP but gov ID works for that purpose. I’m more worried about when they go to a store that doesn’t accept tap.
The only time I’ve gone to my bank in the last 20 years was to get a new card, or to open a new account at a new bank.
Amazing, I have never thought of that! I have always carried my card behind the phone, which is a bit too thick for my liking, but this is such a great idea, thanks for sharing!
I love this.
Wouldn’t the acetone also dissolve the insulation around the antenna wire? So when it touches itself, it shorts itself out, and – electrically speaking – you only have one turn of thicker wire?
Wire that thin is usually insulated with an enamel coating. I’d guess it’s either unaffected by acetone, or just tougher to breakdown. Allow the card to dissolve, but remove and dry asap, don’t let it linger longer than necessary.
Veritasium demoed this a few weeks ago while discussing tap-to-pay security and a vulnerability with apple pay+visa.
Only one way to find out, good thing that these don’t cost any money and you can just ask for a new one.
Maybe take some cash out first to cover any payments you may need to make it it breaks in some way.
If OP is using it and is happy with it, maybe one turn of wire is enough for it to still work, maybe with reduced range?
My guess is it wouldn’t work. On a magnetic antenna, the number of turns don’t affect range, but they do affect the frequency to which the antenna is tuned. It needs to be tuned roughly to the frequency the protocol operates on, otherwise it won’t work. In addition to that, these antennas also need to pick up power, which is also relative to the number of turns.
Seems like something to experiment with at some point. I do have access to test contactless card readers but not sure how they would feel about me destroying the test cards.
Well if it dissolved any insulation, it will not work, as the coil isnt even coiling. It is not a one big coil buy just two ends shorted(or as in the picture, a very small coil. Since this works i can only conclude coating does not dissolve in acetone
It depends on the insulation used, which can vary a lot for thin enameled wire.
Ty, great idea will try it