We are trying to get the whole electronics package as small and compact as possible.  This can mean a lot of fiddling and trimming to get wire lengths exactly right, and assembling and placing the components in a logical order.  Have patience.

Upload the Code

If you haven't done it yet, start by uploading the code to the Trinket.  This will make it easier to test later on to be sure your connections are good.

Prepare the LiPoly Backpack

Carefully clip the JST connector off. Clean up and tin the + and - pads with your soldering iron.


Use a utility knife to cut the trace between the two pads to enable the switch.


Stack the Components

1. Bend the wires around and use a dab of hot glue to secure the green circuit board neatly on one edge of the induction coil.


2. Solder 1 wire into the BAT, #4 and 5v holes.  Twist 2 wires together and solder both into the G hole on the trinket.  Place the trinket on top of the coil and secure it with another dab of hot glue. 

3. Set the battery charger on top of the trinket (don't glue it down yet).  Twist one of the G wire from the trinket and the G wire from the coil together and solder them to the G hole on the battery charger.


4. Attach the power wire from the induction coil into the BAT hole on the charger. 


5. Attach the power wire from the trinket to the 5V hole on the battery charger.

6. Feed the remaining 3 wires underneath the battery charger so they're all on the same side, and trim to about 1".


7. Remove the silicone case from your LED strip and tin the pads.  Solder the 3 wires to their corresponding pads, being sure you're using the "data in" side of the strip.  Secure this with another dab of hot glue.


8. Secure the battery next to the trinket, on top of the coil's green circuit board, with a dab of hot glue.  


Cut the red wire and solder to the + pad on the charger.  Then, cut the black wire and solder to the - pad.  Do NOT shortcut and cut them both at once or you may short your battery with the wire cutters.  These LiPo batteries can pack a wallop, so be very careful not to touch the two wires together!


9. Slide the leads of the mercury tilt switch most of the way through the switch holes, leaving enough room for it to bend down just past flat -- you want it tilted down just a smidge past level, so that the necklace is off (mercury bead is at the top of the tube away from the leads) when the necklace is resting flat on the table. Hold the necklace so the switch is OFF to avoid burning up your components, and solder in place. Trim the leads. Tilt the assembly and the lights should come on.

10. Bend the LEDs into a ring with the lights facing inwards and secure with hot glue.

Test It

Before you go any further, put the necklace through its paces.  Tilt it on and off and make sure you're happy with the action.  If you're not, bend the tilt switch around (gently!) until you are. 

Place it on top of the charging base and be sure the red charging light comes on strongly.   Leave it there a while and be sure it's charging.

This is also a good time to tweak the code and decide on the colors and the brightness.  After the next step you won't be able to access the Trinket anymore so make sure you're 100% satisfied before moving on.

I also added a small piece of electrical tape to cover the lights on the charger and the Trinket, so they won't shine through the center of my necklace.

This guide was first published on Jul 22, 2015. It was last updated on Mar 08, 2024.

This page (Electronics Assembly) was last updated on Jun 24, 2015.

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