Parts Needed

Assembling the cuff requires the following items from the previous steps:

  • Two cut EVA foam pieces
  • Two coils of memory wire with looped ends
  • LiPo battery with USB C connector
  • Electronics assembly of wired QT Py/LED strips


First, place the exterior foam layer on a table with adhesive side facing up and peel away most of the paper. Leave the bits of paper that cover the long tabs at the end. This makes it easier to handle the foam piece without getting stuck to it.

Next, take the electronics assembly, oriented with the LEDs facing downwards, and set the QT Py into the small notch at the edge of the foam. The QT Py should be aligned so that the open end of its USB C connector lines up with the foam edge. Press the foam against the QT Py to ensure good contact

Continue carefully down the length of the electronics assembly, pressing both LED strips into the foam as you go. Move slowly and shape the foam and electronics into a curve with the foam on the outside. The foam cutouts are spaced so each LED is centered on the short edge of a cutout, while the rest of the strip sits behind the foam.

Once the electronics are firmly attached to the foam, place one of the memory wire coils inside the curved foam and press the foam around it. The loop should sit between the edge of the foam and the LED strip without touching either.

The foam is longer than the coils of wire.  Position the coils so that one looped end sits very close to the end of the foam with the QT Py. The other end of the foam with the long tabs will extend past the memory wire.

Press the second memory wire into the other side of the foam, parallel to, and aligned with the first.

Place the taped battery in the cuff so that its USB C connector just sits inside the "U" shaped notch between the long tabs.

Now that the electronics and memory wire are correctly positioned, take the second piece of EVA foam and start to peel back the protective paper from one end. Carefully attach the peeled end to the interior of the cuff, adhesive sides of both pieces together. Start at the end containing the QT Py and be sure that edges and end of both foam pieces are lined up.

Continue peeling back the paper, and pressing the interior foam piece against the exterior one. As you go, push and smooth the adhesive foam surfaces together, while keeping the edges of both pieces aligned. Press the foam around the coils of wire to secure them in place.

The edge of the interior foam piece may extend past the side of the battery with the USB C connector. If so, carefully trim the end of the interior foam piece with scissors so that it just extends just past the LiPo battery. Be VERY careful not to cut or puncture the battery when you cut the foam.

The two tabs on the exterior EVA foam piece wrap back around the edge of the battery into the bracelet interior. This helps secure and protect the battery. Before peeling the paper, bend the tabs back around the interior of the bracelet, and mark the position where they just extend beyond the battery. Trim them at that point.

Peel the paper from the tabs and fold them around the battery, just on either side of the USB C connector. Stick them firmly to the interior of the bracelet by pressing the foam togehter.

Check the Clasp

Now that the bracelet body is assembled, try it out by placing it around your wrist and closing the clasp. It may take a little practice to learn to slip the USB C connector into the QT Py with one hand.

Once closed, check that the QT Py and LEDs are powered. When opening the cuff, pinch the USB C connector and battery between your fingers and slide them away from the QT Py to disconnect.

This guide was first published on Oct 16, 2020. It was last updated on Oct 16, 2020.

This page (Construct the Cuff) was last updated on Oct 10, 2020.

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