What will you do to scare trick-or-treaters this Halloween? There has to be something, right?Well, Harkadi alumni. [CameronCoward] His vacation is certainly controlled by Dead E. Ruxpin, a murderous, tape-controlled animatronic teddy bear.

Readers of a certain age will no doubt see the connection to Teddy Ruxpin, an animatronic teddy bear from the 1980s whose mouth moved as he read stories from cassette tapes. The engineers were clever and used one stereo channel to play the story’s audio and another channel to control the bear’s mouth.

Dead E. Ruxpin took this idea and expanded on it, using the same two channels to send audio and control three servo motors that move the arms and mouth. How can this be? By sending a tone constructed from one or more frequencies.

Essentially, [Cameron] Assign a frequency to each action: mouth open/close, left and/or right arm up or down. Of course, these are all synchronized to specific points in the audio, so Dead E. isn’t just moving randomly, he’s dancing to the music.

The bear is actually a hand puppet that leaves room for a 3D printed armature that holds the RP2040 and servos and of course moves the puppet’s parts. We can’t decide if we prefer the bulging, bloodshot eyes, or think the cute raw eyes make the bear more terrifying. Anyway, check out the build/demo video after the break to see it in action.

Do you like Teddy Ruxpin now? Here’s more information about those scary bears. Don’t forget, the Halloween Hackfest runs from now until October 31st.