Prototype · October 2026

Two players influence a steel ball with EEG

Two players sit at opposite ends of a table, each wearing a single-channel EEG headset. A steel ball moves across the covered playing surface toward the player whose signal is currently less settled. The round ends when the ball reaches either end.

Beneath the cloth, a belt-driven linear axis moves a magnet under a clear acrylic sheet. The magnet pulls the ball along the surface; the mechanism remains hidden during play.

1steel ball
2black cloth over acrylic
3stepper motor
4magnet on the carriage
51000 mm linear slide
6six 5 cm risers

Player Alevel relative to baseline

Player Blevel relative to baseline

Simulated signals for two players. Drawn to scale. Part of the cloth is cut away in the drawing to show the slide underneath.

How it works

From headset to motor

HeadsetsEach player wears a battery-powered, single-channel EEG headset, with the electrode embedded in a head strap. The headset sends samples to the laptop over Wi-Fi.
SoftwareAt the start of a session, the software records a two-minute baseline for each player. During play, it compares each signal with that player's baseline and smooths the result over roughly ten seconds. The difference between the two values determines the ball's target position.
Motion systemThe laptop sends the target position over USB to a motor controller. A stepper motor moves a magnet along a linear rail beneath the acrylic, pulling the steel ball across the surface.

Parts

Parts list

Motion system

Part	Qty
Belt-driven V-slot linear slide, 1000 mm, with NEMA 17 stepper motorone axis of a 3D printer; 880 mm of travel	1
TMC2209 stepper driver	1
100 µF capacitoracross the motor supply	1
12–24 V power supply, 2 A or morepowers the motor and driver only	1
Motor controller, Arduino Nano/Uno or ESP32receives the target position over USB; AccelStepper library	1
Limit switchhomes the carriage at start-up	1
Neodymium disc magnetsmounted on the carriage; two sizes, to test against the sheet and cloth	1 set
Jumper wires	1 set

Playing surface

Part	Qty
Acrylic sheet, 61 × 122 cm, 5.6 mm thicksold as 24 × 48 × 0.22 in	1
Risers, about 5 cm tallat each corner and mid-span on each long edge	6
Washersset a 2–3 mm gap between the magnet and the sheet; the sheet rests on the risers unfastened	1 set
Black cloth	1
Steel ball, 25–50 mm	1–2

Headsets

Part	Qty
BioAmp EXG Pill sensor board	2
ADS1115 analog-to-digital converter	2
ESP32 Wi-Fi board	2
Battery pack	2
Headband with gold-cup electrodes and ear clip	2
Conductive EEG paste	1

Computer

Part	Qty
Laptopprocesses both EEG signals and sends the target position over USB	1

Development log

October 1Robert Alexander provided the brief with two proposed mechanisms: a tilting surface and a concealed moving magnet.
October 2We developed both concepts far enough to compare their dimensions, components and signal-processing requirements.
October 2We selected the concealed-magnet design as the primary prototype. We will also build the tilting version for comparison.
NextComplete the delivery specification and begin bench testing.

Constraints

Prototype constraints

Each headset is battery-powered and communicates with the laptop over Wi-Fi. Players are not electrically connected to the table or motor supply.

The prototype is an experimental game interface, not a medical, diagnostic or wellness device. It uses our existing single-channel EEG hardware and signal-processing code.

MindWave Therapeutics 2026