Cut LEDs

Decide how long you want your scarf to be.  Mine is just shy of 1.5 yds long, but if you're tall you may want it longer.  

The gemma board will run up to around 100 pixels.  It doesn't have the processing power for more, so if you have more than that in your scarf you may want to use a Flora or a Circuit Playground

Lay out the fun fur face down and mark your scarf length on the back.  Then lay your LED strip on top of the fur and cut it carefully to the same length along the cut line. 

LED Wiring

Look at the LED strip and figure out which is the "in" end (the arrows will be pointing down the strip away from this end).

If you're using a brand-new strip and there's a connector soldered on, your job is easy.  Cut off the connector so you have bare wires to solder onto the gemma.

If there's no connector soldered on, you'll need to add your own wires.


Tin the three solder pads with your soldering iron.  Strip a tiny bit of insulation off the end of three wires and solder them on to the three pads.  I used red for 5V, yellow for DI, and black for G.


Membrane Switch Wiring

Take your jumper wire and snip it in half.  Slide one pin into the center slot and the other into the left-hand slot of the membrane switch.  They don't like to stay put, so slide a piece of heat shrink over the whole connector, fill the heat shrink with hot glue, and shrink it  down with your heat gun.


Plug your battery into your gemma.  Secure the wires with alligator clips (or just wind them tightly in place).  Your lights will come on -- this is a great time to test your switch and make sure all your lights are working correctly before you solder everything together.

Gemma Wiring

Solder all 5 wires to the Gemma:

  • Switch left pin to Gemma D2
  • Switch center pin to Gemma GND
  • LEDs 5v to Gemma Vout
  • LEDs GND to Gemma GND
  • LEDs DIN to Gemma D1

Notice that you have two wires both going to the GND pad on the Gemma!  Be sure they're both in place before you solder.


Now it's time to seal up the LED strip to keep it weatherproof and minimize breakage.  

Slide a piece of clear 1/2' heat shrink over the LED strip.  With the heat shrink positioned over the solder connections, fill up the area inside the heat shrink with hot glue.  

Then, take a heat gun or hair dryer and point it at the heat shrink to shrink it down.  It's best to do this quickly, before the glue sets up.  

This will create a plastic seal that will greatly increase the strength of your connections. 

Do the same at the other end of the LED strip.

This guide was first published on Dec 17, 2014. It was last updated on Feb 29, 2024.

This page (LED Assembly) was last updated on Dec 11, 2014.

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