Wiring and Soldering

Here’s the schematic when using a Gemma board. Simplicity itself! The battery isn’t shown here…it simply plugs into the JST connector:
This diagram uses the Gemma v2 but you can also use the Gemma M0. The only change to be aware of for the Gemma M0 is that the optional replay button is touch sensitive on the Gemma M0. This means that no physical button is necessary and any conductive materials can be used to replace the animation
A couple extra steps are required if using a Trinket board (3.3V or 5V doesn’t make a difference, the connections are the same):
Since there’s no JST battery connector on the Trinket, we’ll need to make one using the battery extension cable. Cut it a couple inches from the socket end (where the battery plugs in), separate the red and black wires about halfway, and strip about 1/4" of insulation from the ends.

The red and black wires each need to connect to two places in the circuit: red goes to BAT+ on Trinket and + on the backpack, while black goes to GND and –. These connections require a split inline splice. Even a regular 1-to-1 inline splice can be tricky for a novice, 2-way is an extra challenge. It’s a little easier with narrow-gauge wire (e.g. 26 ga.).
An example of a three-way inline splice (this is from another project — we’ll be doing just a 2-way splice, but the technique is the same):

Line up the 2 wires on one side and twist them together. Slide heat-shrink tube as far down as possible. Then bring in the power wire from the opposite direction and twist around the others. Solder and heat-shrink the connection.

Work slowly and methodically, remember to slide the heat-shrink tube on FIRST before joining the wires, and use proper soldering technique: heat the wires and apply the solder there; don’t move a glop of solder from the iron to the connection.
This guide was first published on Oct 01, 2013. It was last updated on Oct 01, 2013. This page (Wiring and Soldering) was last updated on Oct 22, 2019.