With thicker material, you might want thicker magnets. This has several advantages: you get more strength from the magnets, you potentially avoid issues with credit cards by shielding some of the magnetic field from reaching outward, and it sticks much less to steel surfaces on the outside of the wallet or money clip. When we added two layers of steel on the outside of the magnets, we felt even more strength. Of course, the card stock we used is much thinner than their leather. That’s a thinner magnet than what we found in the money clips we took apart. In the rough prototype we made in the video, two 1” x 1/2” x 1/16” thick BX081 magnets felt nice. The force you feel between the two magnets depends on the distance. In between your two magnets, you’ll have at least two layers of material (leather?) and some amount of cash. Adding a layer of steel blocked the fields nicely, but does add weight to the wallet. We found that some of those off-the-shelf clips and wallets are probably OK with durable, high coercivity cards, but can erase the low coercivity cards like hotel keys or subway passes. We measured the field strength in a few of them, and then tested them with high and low coercivity cards. Naturally, we had to get our hands on some magnetic money clips to test. Keep the magnets a safe distance away from the stripe, add a layer of steel between the magnet and the card, or both!ĭo not put credit cards between the two magnets! The field is very strong there. With either card type, use distance or shielding to avoid scrambling the stripe. It’s easier to erase a low-co card (~300 gauss) than a hi-co card (~4,000 gauss). There are two types of credit cards: The low-coercivity cards used for hotel keys, subway tickets, etc., and the more durable, high-coercivity cards used for bank and credit cards that get more long-term use. We talked about this phenomenon in way too much detail in our earlier article, Credit Cards and Magnetic Stripes. It's nice if your wallet doesn't erase your cards! While many payment processors are using the more magnet-proof chip, the old magnetic stripe is still used. Magnetic fields can scramble the data on a credit card’s magnetic stripe. High coercivity cards are usually black or silver.
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