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Shining a light behind this metal credit card.
(thelemmy.club)
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this post was submitted on 15 May 2026
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Mildly Interesting
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Electrical Engineer here. Pretty sure the slit is to break up the metal in the card so it won't interfere with NFC.
If you look at an NFC antenna, it's a big coil of wire. It's energized by an oscillating magnetic field that passes through it. Faraday's Law dictates that when a magnetic field oscillates, an electric field will form around it. This electric field generates a current in the antenna that powers the NFC chip.
In a metal card, the current will flow in the card instead and draw energy away from the NFC chip. This slit blocks that current flow so that the current flows in the antenna instead.
Any reason it's a staircase instead of just a simple. Straight line?
I believe that minimizes capacitance. My question is why diagonal at all. Maybe it helps with adhesion during the manufacturing process?
Capacitance between turns, specifically. Provides e-field shielding too.
~~It's an antenna & it needs to be a certain length - making it a bit gay just adds enough pizazz (length) and it's the ez thing to do from a designers pov.~~
Oh, no, the metal ones do in fact use the metal as an antenna?? Can't really tell (but I would guess not).
yt/wyj7r_C51UU&t=115, yt/P5aszRLpa3Y
I though it was like this:
So the pattern of the cut is maybe structural (harder to bend with the plastic inside it bcs it's longer?) or just perhaps a CNC simplification.