Raspberry Pi Book of Making 2027: Animate a Halloween Skeleton With a $4 Pico

Raspberry Pi has shared a Halloween project from the pages of its Raspberry Pi Book of Making 2027: a 90cm glow-in-the-dark skeleton that moves its arms and legs, driven by a $4 Raspberry Pi Pico. The build is published on the Raspberry Pi blog, and the book is available at an introductory price of £9.99.

The project is aimed at makers who want a decoration that reacts to people rather than just hanging there. A distance sensor detects when someone comes close, and servos handle the movement. If you would rather not build a skeleton, the same techniques can be adapted to animate other decorations.

What you need to start

The skeleton itself came from AliExpress and cost about £3. The important detail is that it must be a “2D” skeleton, where all the joints move in the same plane — Raspberry Pi notes that 3D skeletons are more anatomically accurate but harder to animate, and that listings can be unclear about which type you are buying. A 90cm, glow-in-the-dark skeleton at roughly £3 should be the right one.

The skeleton arrives as ten separate parts: two for each limb, one body and one head. Only the hip and shoulder joints get motors; the knees and elbows are left loose to flail.

You will also need a firm backing board of at least 45 × 21cm — the project used Oriented Strand Board (OSB), though plywood works too — plus 9g servos, a distance sensor, 3.5mm screws shorter than the board is thick, mounting hardware and a cable tie. Raspberry Pi recommends sticking with the small servos, since larger ones may draw too much current unless you add an external power supply.

Red eyes and a Pico in the middle

For the eyes, the build uses two 12mm WS2811 LEDs cut from a 5V chain, wired for red. The controller is a Raspberry Pi Pico — the project used a Pico W, but the wireless interface is not used, so any model works. The Pico needs to be mounted so the USB port stays accessible.

The back board gets 12mm holes for the eye LEDs and 10mm holes near each joint to route the servo wires, and it can be painted black so the skeleton stands out.

One step has to happen before the limbs go on: because servos typically turn only about 180 degrees, you need to wire them up and rotate them to a known position first, otherwise you may not be able to move them into the right place once the arms and legs are attached.

The full walkthrough, including how the servo horns are screwed to the limbs and how the servos are mounted vertically, is on the Raspberry Pi blog. The Raspberry Pi Book of Making 2027 is on sale at the introductory price of £9.99.

Sources

• Animate a Halloween skeleton — Raspberry Pi Book of Making 2027 — Raspberry Pi News