Carefully trim flush any protruding wires from the underside of the Trinket and LiPoly backpack boards.

Inspect the connections carefully for any signs of shorts or cold solder joints. Soon these boards will be tucked away and very difficult if not impossible to repair.

“Tweezer comb” the wires to straddle the USB port. Take your time so they’re not tangled. There should be four wires on either side: one each of power, ground, data and clock. Tape each group down as you work so they don’t run wild.

Carefully slot the Trinket into the printed insert, removing the tape as you go.

Once the Trinket’s in position (the USB port should protrude just a couple millimeters), tape the wires together in a bundle.

Tip the LiPoly backpack up and squeeze a dollop of either E6000 glue or 5-minute epoxy on its underside.

Slide the backpack into place (the edge should be flush with the insert) and clamp in place with a clip, clothespin, some tape, whatever you have handy.

Do the same for the Trinket, then slide into place and clamp.

The edge of the board should protrude from the insert just the tiniest bit — a millimeter at most.

Glue the power switch and mode button in place. This step really calls for epoxy, not E6000.

Make sure the tips of these controls are flush with the base, not protruding.

Don’t glop them up too much! The sides of the switch have openings where glue could get in and interfere with its operation.


E6000 requires hours to reach full strength. This is an excellent time to take a break or stop for the day. Put the pieces in the garage or out on a balcony while the glue dries…the fumes aren’t healthy to breathe. Turn off the soldering iron, wash your hands because you’ve been handling all this stuff, then go to bed, go for a bike ride or have a Pop-Tart®.

We’ll continue below. In the meantime, here’s another picture of Erin “Firepixie” spinning POV-poi to keep you motivated:

Almost there!

Solder LED Strips

Using pliers, add a little bend to the tips of the LED strips (where the solder pads are) to help them fit in the tube. Then position them over the poi insert and hold in place temporarily with tape or rubber bands.

Those notes you took earlier about the LED strip pinout? Here’s where you’ll need them…

Tin each pad on the strip with a tiny bit of solder.

“Tweezer-comb” the clock and data wires on one side over the corresponding pads on the LED strips, trim length to fit (a few mm slack is OK), then strip just a tiny bit of insulation and tin the tips of the wires. Using tweezers to hold the wires, solder them to the LED strips. Make sure the solder joints are smooth and shiny, not “cold” joints.

Next, repeat the procedure with the power and ground wires. Notice how on each side we’re connecting half the wires for each strip; this is normal.

Turn the poi insert over and repeat these steps for the four wires on the other side. Clock, data, power and ground.

Dry Run

The moment of truth!

You should have already loaded the poi sketch onto the Trinket microcontroller(s). If not, skip ahead to the “Code” page for a moment, fetch that software and program the boards.

Remove the tape from the LED strips.

Pivot one LED strip out slightly (if any solder connections break, that’s a cold joint, fix it), then carefully plug the LiPoly battery into the backpack.

DO NOT use a metal tool for this! It’s too easy to short across the battery connections. Use a toothpick or other non-conductive implement to push the plug into the socket.

Flick the power switch (if it’s not already on — look for the green power light on the Trinket board). After a few seconds, the LEDs should start doing things!


If the LEDs don’t come on, here’s some things to check…

Green power LED on the Trinket doesn’t light with the power switch in either position: disconnect the battery immediately! It may be an electrical short between + and ground. Connect a USB cable between your computer and Trinket. If the light comes on then, it’s probably not a short, just a spent battery. Re-connect it and allow some time to charge.

Green LED is on, but the LED strips do nothing: connect a USB cable and make sure the poi sketch is loaded on the Trinket board. If there’s still no response, probably a wiring mistake…either the clock and data wires are reversed, or they’re connected to the wrong pins on the Trinket (should be pin 1 for data, pin 2 for clock).

Only one LED strip is active: wires are probably in the wrong order on the unlit strip.

Power switch won’t budge: glue has seeped inside. Use more force to try to break it free. If it’s completely wedged, there’s no choice but to break it down and solder in a new switch.

Power is always on, switch does nothing: on the LiPoly backpack board, the copper trace between the power switch connections has not been cut.

Once any issues resolved and the LEDs are doing things as expected, switch it off for the final assembly steps…

This guide was first published on Jul 13, 2015. It was last updated on Jun 21, 2015.

This page (Glue and More Soldering) was last updated on Jul 10, 2015.

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