LED Assembly

Look closely at your LED strips and find the "in" end (arrows pointing away).   Carefully count out the number of pixels you want in your bandolier.  Count them again!  Then cut the strip and the silicone sleeve between the copper pads.

 

"Tin" the pads on the IN end of each strip by adding a blob of solder with your soldering iron.

Cut two red, two black, and two white wires to about 3 inches long.  Strip a tiny bit of the shielding off one end of each wire, then "tin" the wires too, adding a little blob of solder on each one.  Solder the wires to the NeoPixel strips:  red to +5V, white to IN, and black to GND.

Be sure to check the labeling on your strips and match up the wires to the labels.  Some batches of NeoPixels may have the pads laid out in a different order, so follow the pin labels rather than physical positions.  If you wire them up incorrectly you could damage your strips or your Gemma.

Trim the wires so they're all about 2" long.  Strip the loose ends.  Twist the colored pairs together, then solder the red wires to Gemma's Vout pin, the white wires to D1 and the black wires to GND.

Plug your battery in and flip the Gemma’s on/off switch to ON.  If all your LEDs come on, it's time to secure everything to make it robust.

Slide a piece of 1/2" clear heat shrink over the wire connection.  Squirt some hot glue inside the silicone sleeve, and while the glue is still wet, use a heat gun to shrink the heat shrink down.  This will create a solid plastic stopper on the end of your strip so the wires will never pull out or get disconnected.

Repeat with the other strip, and be sure to seal the bottom ends with hot glue and heat shrink the same way.

Disconnect the battery when not in use. Gemma’s on/off switch only turns off the microcontroller…but power is still connected between the battery and LED strips. NeoPixels draw a tiny bit of power even when they appear “off,” and this will slowly drain a connected battery.

Troubleshooting

If your LEDs don't come on, or don't look right, here are a few things to try:

  1. Check to be sure you soldered to the IN end of the NeoPixel strips.  The strips won't work if you solder them to OUT.
  2. Be sure the black wires are connected to GND on both Gemma and the LED strips, and the red wires are connected to +5V and Vout
  3. Check to be sure your battery is charged
  4. Try re-uploading the code to the Gemma
This guide was first published on Mar 29, 2018. It was last updated on Mar 29, 2018. This page (LED Assembly) was last updated on Jul 25, 2019.