The bracelet is created from folded figure-8 shapes cut from leather or rubber. You can easily draw it yourself, or download this image and print it out ~1 inch wide (or trace the screen!):

Draw or glue the template to a piece of thick paper, illustration board, or piece of cardboard. Cut out the figure-8 shape using a sharp utility knife or craft blade.


On the wrong side of your material, trace the template many times and carefully cut out a small pile of pieces using sharp scissors.

To create the bracelet closure, cut out two special pieces with elongated tabs as shown:

Use a snap setting tool to attach the snap parts, or use velcro tape instead.

Sandwich the two pieces wrong sides together, and place a figure-8 through the center hole. Fold the figure-8 flat so it creates a new sandwich for inserting the next piece. Repeat to build up a few links.

GEMMA fits snugly between the layers, which expose the power switch but hide the USB connector and JST battery connector. Slide GEMMA in from the side, with digital pin 1 facing towards the working end of the chain.

Poke a small hole in the center of the next link and insert one leg of the resistor (doesn’t matter which), then also through GEMMA’s pin 1. Twist the lead so it makes good mechanical contact with the solder pad.

Next up is the transistor. Splay the leads away from each other, and use pliers to carefully bend them into place. Pictured above, the flat side of the transistor faces the same way as the flat side of GEMMA. Solder the base and emitter pins, being careful not to singe the material of the bracelet (although black leather can be very forgiving in this regard).

To prepare the motor/diode assembly, set up your diode in a third hand tool and tin the leads close to the diode itself. Hold the delicate motor wires up to the leads and remelt the solder to affix the motor.


Use heat shrink tubing to insulate the leads and help protect the tiny stranded wires connected to the motor.

Solder the motor/diode assembly to the transistor’s remaining pin (collector) and GEMMA Vin. The diode leads travel around the next link in the chain, concealing and protecting the circuit.

Last updated on 2015-11-23 at 05.38.08 PM Published on 2015-06-10 at 12.44.49 PM