Using the high-density NeoPixel strip (144 LEDs/meter), one of our pairs of glasses required 20 LEDs, another required 22. The 60 and 30 LEDs/meter strip would have proportionally fewer LEDs.
The Trinket/Gemma board will connect to the “in” end…that would be to the left in this view.
This doesn’t apply to 60 or 30 LEDs/m strip — these have connection points on both sides of the cut line.
The circuit is incredibly simple, with just a few connections needed…
If using Trinket: Though data moves only one way through a NeoPixel strip, power transfers both ways. We use this to our advantage here, making the strip itself function as a power bus for the whole circuit. Cut the JST battery extension cable about 4" (10 cm) from the plug end (the end that connects with the battery). Strip the ends of the wires, give them a twist and then insert them anywhere along the strip; black wire to –, red wire to +, and solder in place.
The wires should be inserted back to front (soldered on the LED side); the diagram below has the wires on the front just to show how they’re routed.
At the input end of the strip, three wires are then connected between the strip and Trinket board: – (minus) on the strip to Gnd on Trinket, + on the strip to 3V (or 5V) on Trinket, and the remaining connection to Pin #4 on Trinket.
If using 60 or 30 LEDs/meter NeoPixel strip, the connections are in a different order than shown here, and are labeled GND, +5V and DIN (rather than –, + and unmarked, respectively).
If using 60 or 30 LEDs/meter strip, the note above about pin order applies to Gemma as well.
After soldering, all of the protruding wire points were trimmed.