Circuit Diagram

This diagram uses the Gemma v2 but you can also use the Gemma M0 or the original Gemma v1 with the exact same wiring!

A see-through bracelet would show off the circuit above:

  • ~220-1K ohm resistor to GEMMA pin 1
  • NPN transistor base (center pin on PN2222) to resistor
  • NPN transistor emitter to GEMMA ground
  • NPN transistor collector to motor black wire AND diode anode
  • GEMMA Vin to motor red wire AND diode cathode (gray stripe)
  • Battery plugs into tan JST port

It's difficult to fit the circuit inside the bracelet if you build it first. We'll be building it as we go, interlocked with pieces of the bracelet for the most compact fit.

This guide was first published on Jun 10, 2015. It was last updated on Jun 10, 2015. This page (Circuit Diagram) was last updated on Nov 21, 2019.