This is a case of knowing your audience: my friend Matt is deeply involved in the world of creative DIY electronics, and appreciates a good (ie. terrible) pun. So for Matt’s bachelor party, fellow groomsman Ethan and I arranged for a stripper to pop out of a cake — but in this case, it was a wire stripper (an electrician’s tool) animated by a jumble of electronics, in a cake which we built.
After dinner, we lit the candles on the cake (it was also Matt’s birthday), and in the dim light of the BBQ joint, the illusion was convincing.
But once Matt made his wish and blew the candles out, the top opened up revealing a stripper dancing on a stage, complete with flashing lights and music!
The cake’s frosting is a sheet of white foam material from an art store, held on with Velcro stickers. The decorative chocolate frosting is brown caulk.
Beneath the frosting is a laser-cut plywood frame, with threaded dowels, nuts and washers. The top has a hinged lid with the stage slotted and glued inside.
A hidden power switch in the back provides 6V from four AA batteries to an Arduino Duemilanove microcontroller, which we programmed to run the show.
Once the stage is up, the lights change to a cycling rainbow pattern. We used four of Adafruit’s 8-NeoPixel strips, all chained together in series. The first NeoPixel strip is on stage, lighting up the wire stripper.
Other NeoPixel strips are on the middle ring, lighting the inside of the cake in all its mad scientist glory. The white foam frosting is translucent, so the whole cake glows brightly on the outside.
Beneath the stage, a motor with an elliptical wheel makes the wire stripper kick its leg and dance the can-can.
The original plastic geared motor for this section melted when we tried to solder on the power cables. The Radio Shack replacement didn’t have enough torque. So we used a spare littleBits motor. It later burned out because we’d run out of time and didn’t regulate the voltage, but by then it had done its job.
Music is from a chip I ripped out of a greeting card years ago, wired up to a small speaker. It plays the theme from “The Good, The Bad, and The Ugly.”
When you’ve had enough of the show, you can reach in through the top and press a microswitch (center of the picture, on the middle ring), which stops the dancing, turns all the lights to blue, and closes the cake up again.
We built the whole thing in very little time, and it has a cobbled-together, hot glue aesthetic. Not the finest engineering, but Matt loved it, which is all that matters.