Connected toy · Prototype

Kai

A kendama that knows which trick you just landed.

Motion sensing, Bluetooth, a speaker and USB-C charging, on a round board small enough to sit inside the kendama. We designed the board and its firmware, and five have been assembled.

Where it stands

Prototype · Board testing in progress

Done: Five boards assembled
Done: First board passes its self-test: radio, sensor, buttons and flash
Still to do: Testing the other four boards
Still to do: Charging, sound and power consumption
Still to do: A body that fits the board

Electronics

Round board with an ESP32-C3, motion sensor, audio amp and battery charger.

Firmware

Self-test firmware that checks each board and logs the results.

CAD

Carrier, cap and button parts modelled around the board.

Gallery · Renders and real hardware

A real assembled round circuit board on a panel — **Photo** A real assembled board.

An X-ray image of the round circuit board showing its chips and antenna — **Photo** An X-ray of the first board, used to inspect solder joints.

Exploded view of the kendama base showing the battery, board and speaker — **Concept render** How the parts stack. Play time shown is a target.

A translucent kendama with its battery and board visible inside — **Concept render** Where the electronics sit.

The kendama body in the film and renders is a concept shape, not the production part. Play time and the spoken coaching are design targets and have not been tested yet.

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