DIY: Create Your Own Public Transport Card

If there How to DIY a Public Transport Card?

If you're interested, take a look at this article.

Materials Needed:

a. A lid from a Yida gum container or another similar lid.

b. 2 meters of enameled wire with a diameter of 0.2 mm; it should be flexible yet sturdy.

c. A soldering iron.

d. Epoxy resin.

Steps:

Use your phone's flashlight to illuminate the surface of the damaged public transport card and locate the chip. Carefully cut it out with scissors, taking care not to bend it. The chip is very small and thin, so handle it gently. Tin the pads on both ends of the chip.

Check how many turns the coil needs (this is crucial). In this case, it requires six turns.

Calculate the Inductance:
The formula is:

Inductance = Inductance Coefficient × Area × (Number of Turns)².

You just need to ensure that the area × (Number of Turns)² after modification is equal to the original.

The coil on the card is rectangular:

L=ε×80×50×6×6=144000εL = ε × 80 × 50 × 6 × 6 = 144000εL=ε×80×50×6×6=144000ε

The diameter of the Yida lid is 40 mm:

L=ε×3.14×20×20×N2=1256ε×N2L = ε × 3.14 × 20 × 20 × N² = 1256ε × N²L=ε×3.14×20×20×N2=1256ε×N2

This gives you N≈11N ≈ 11N≈11.

Roll an A4 sheet of paper into a slightly smaller cylinder. Wrap the enameled wire around it for 11 turns and use hot glue to secure it lightly so it doesn’t unravel when you remove it.

Strip the insulation from both ends of the wire and tin them. Then, solder them onto the two pads of the chip.

Place the coil in the groove of the lid, ensuring it lays flat. You can use a bit of glue to secure it and prevent it from lifting during the resin pouring process.

Start pouring the transparent epoxy resin.

Wait for the resin to dry completely.

Final Product:

Once everything is set, you'll have your finished product.

After testing, the public transport card should work normally. You're done!