Connect switch to Lipo Backpack

Let's start off by setting up the power circuit. Measure and cut two 26AWG wires. Strip and tin the tips of each wire. Trim the leads from the slide switch short and solder the two wires to them. Apply two pieces of heat shrink tubing to insulate the exposed leads. Cut the traces with the label pwr switch on the Lipo backpack. Connect the two wires from the slide switch to the power switch pins on the Lipo backpack.

Connect Lipo Backpack to Teensy

Cut the trace on the pads of the Teensy noted in the wiring diagram. Measure and cut three 26AWG wires. Strip and tin the tips of each wire. Connect the following pins together. 

  • 5V from lipo backpack to VUSB on Teensy.
  • GND from lipo backpack to GND on Teensy.
  • BAT from lipo backpack to BAT+ on Teensy.


Trim the leads short and apply solder to tin them. Measure and cut two 30AWG wires. Strip and tin the ends of each wire. Solder wires to shortened leads. Add heat shrink tubing to insulate the exposed leads.

Connect Ribbon Cable to Display

Grab a set of jumper cables. Remove the connectors using wire cutters. Peel, strip and tin the ends of each wire. Tin the pins on the TFT display and solder the wires to them. Write the colors to each pin for reference.

Connect Display Wires to Teensy

Follow the wiring diagram and tin the pins on the Teensy. Solder the wires from the display to the Teensy using the wiring diagram and your color reference notes.

Connect UV LED to Teensy

Tin wires to 3.3V and GND pins on the Teensy board. Solder the positive wire from the UV LED to 3.3V and the negative wire to GND on the Teensy.

Connect Wires to Pushbutton

Measure and cut two 30AWG wires. Strip and tin the ends of each wire and solder them to the leads on the pushbutton.

Mount Pushbuttons to Panel

Unscrew the hex ring from the wired pushbutton. Insert the wires through the hole on the panel. Press the pushbutton into the hole and apply force to push it all the way through. Flip the panel over and thread wires through hex ring. Screw the ring tightly on to the pushbutton and secure it in place. Remove ring from second pushbutton and insert into the other hole. Thread the wires from pushbutton through the smaller hole.

Connect Pushbutton to Teensy

Secure the Teensy to a pair of helping third hands. Solder the wires from the pushbutton to #0 (wink left) and a ground pin on the Teensy.

Block LED from Teensy

To remove light leaking from the inside of the enclosure, paint the LED black using black acrylic paint using a tooth pick.

Block Light from TFT Display

Use a piece of black electrical tape to cover the bottom of the TFT display. This will help block any light leaking from side the enclosure.

Block light leakage from the components is only necessary if the enclosure is printed in opaque/transparent filament.

Trim Battery Wire Short

We’ll need to trim the cable short from the battery to allow space in the enclosure. Cut the red positive wire, then the black negative wire from the battery. Strip and tin the ends of each wire. Apply pieces of heat shrink tubing, then solder the wires back together.

Ensure they’re cut one at a time to avoid shorting the battery. The positive and negative wires mustn't touch, ever!

Apply Tack to Components

To mount the Teensy and Lipo backpack PCB’s to the panel, we can use tack. Using tack allow you to shift the components around for optimal placement. You can optionally use epoxy or E6000 adhesives to permanently secure the boards to the panel.

Install Display to Panel

Fit the wires from the TFT display in between the bottom left walls (Peel apart the wires if needed). Lay the display over the two pushbuttons with the pins facing towards the top of the panel.

Mount Teensy to Panel

Place the Teensy PCB below the display, underneath the bottom wall. Press it down to secure the tack to the panel.

Install Switch to Face

Insert the slide switch through the hole near the bottom of the face piece (chin). The tolerances should be pretty tight to hold the switch in place, but you can optionally apply adhesives to permanently secure it.

Mount Battery to Panel

Add a piece of tack to the lithium polymer battery. Place it behind the slide switch and press it down to secure it onto the panel.

Mount Lipo Backpack to Panel

Stick the Lipo Backpack below the Teensy board. Press it down to secure it to the panel.

Install Unicorn Horn

Insert the unicorn horn through the opening near the top of the face piece. Apply force to push the unicorn through the opening. The tolerance should be tight, but if you find it loose, you can apply adhesive to secure it in place. Insert the LED through the hole on the bottom of the horn - If it’s too loose, add some tack/glue to hold it in place.

Install Wings and Cabochon

Place the wings over the sides of the panel. Line up the holes on the wings with the clips on the panel. Press them down to hold them in place. Lay the cabochon over the display.

Install Face to Panel

With the wings and cabochon installed, carefully lay the face part over the panel. Line up the lip of the panel with the inside of the face part and press them together - it should snap into place.

Ensure wires are nice, tidy and completely enclosed inside the enclosure. Avoid kinking or clipping the wires when joining the halves together.

Secure Face to Panel

While holding the parts together, insert #4-40 3/8 size flat Phillips machine screws into the mounting holes on the back of the panel. Tightly hold the two parts together while fastening the screws all the way through until they’re flush with the surface.

Make sure all of the wires are kept inside the enclosure and out of the way from the mounting holes!

Test Power Switch / Circuit

If everything fits nicely, flip the switch to power on the circuit. Slowly push the cabochon inward to actuate the pushbuttons. If everything is neatly in place, the eye should wink!

If the screen turns white when pressing the eye, some of the wires are probably shorting out. Take it apart and diagnose the wiring. Ensure the wires are neatly nestled behind the display.

Installing Doorbell

Now its time to install the doorbell. If you haven’t already, you should poke around your existing doorbell and see how it’s being mounted. If it’s using the same mounting plate like in this project, congratulations! You’ve won the maker lottery.

Most doorbells probably aren’t standardized, therefore they’re all going to have different mounting holes.

Once you’ve figured out how to mount the plate, it’s relatively easy to stick the enclosure to it - I used double-sided foam tape. The mounting plate has a large opening in the center to allow the two pushbuttons to fit into. The mounting plate itself is secured to a metal bracket thats fixed to the wall using two screws.

My original doorbell was a slightly larger, so you can see how the non-painted areas show through. There's only two wires that need to connect to the second pushbutton. Since the pushbutton doesn't have specific polarities, it didn't matter which lead is positive or negative. Just be careful that those wire DO NOT touch the wires from the pushbutton that triggers the eye wink. NEVER connect the doorbell wires to the same pushbutton - that would totally cook the Teensy board.

This guide was first published on Oct 29, 2015. It was last updated on Oct 29, 2015. This page (Assembly) was last updated on May 16, 2019.