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Necessity is the mother of invention
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this post was submitted on 07 Jun 2026
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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!
Peak Lemmy behaviour I love it
"Please use chip reader".....
Wow.
Have you ever run into difficulty with needing to authenticate with chip+PIN? Like while traveling?
That would be my big with with this; it would make it very difficult to pass a PIN check, to say the least!
Super cool idea. I might just try it myself and see if I run into issues.
What I modified was in fact a contactless payment token. It had the form factor of a payment card, but it only does NFC.
I have another card for chip+pin.But I almost never use it where I live, because all limits were lifted on contactless payments a few years ago. If I try to pay something really expensive contactless, it will ask me for the pin - which is specific to the payment token.
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...
Next time someone calls me a maniac, I'll show them this.
Definitely doesn't live up to their username.
You are fucking crazy. I love you.
The fact it's secured with a piece of sellotape is just *chef's kiss*.
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.
Depends on how fussy the bank is, but yeah.
You clever, I like.
I am surprised that no one sells cases designed for exactly this
Fairphone 6 has an add-on exactly for this.
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!
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 of antenna 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.
I love this.
Ty, great idea will try it
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.
I was thinking about this, and there are two easy workarounds, I think:
But, in either case, I do think you might run into a different issue: automated fraud detection sometimes requires me to chip+PIN, even for transcribed below the tap limit. This has happened to me when traveling. I don't think there would be any way around that, and if you then fail to authenticate with chip+PIN, it's reasonable to think that the bank would lock your card for contactless payments until you successfully authenticate the card again with chip+PIN. (To be clear: this is only speculation; not sure if that would be an issue in practice.)
So, I suspect that whether this would work or not might depend on your institution (or maybe jurisdiction?)
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.