Sensors & Outputs
Brain side: Octopus 16 (Web Bluetooth)
A round 16-channel board whose spring-loaded pogo pins are the electrodes, so there's no gel, no cap and no cables. A Seeed Studio XIAO ESP32-S3 on top streams the signal over Bluetooth, and the browser turns it into band power.
| Reading | Meaning |
|---|---|
| Band power | δ θ α β γ, relative (share of total power) |
| Focus | Uncalibrated index, Beta / (Beta + Theta) |
| Relax | Uncalibrated index, Alpha / (Alpha + Beta) |
| RMS | Signal size in µV |
| Strongest band | The band with the most power right now |
| EEG ok | Green when RMS is between 2 and 200 µV |
| Band | Range |
|---|---|
| δ delta | 0.5–4 Hz |
| θ theta | 4–8 Hz |
| α alpha | 8–13 Hz |
| β beta | 13–30 Hz |
| γ gamma | 30–100 Hz |
Blinks and jaw clenches raise RMS and gamma. That's muscle, not brain activity.
Room side: starter kit (Web Serial, 115200 baud)
Elecrow's All-in-One Starter Kit for Arduino (SEA0004T): an Arduino Uno-compatible board with sensors and outputs already mounted in one case. It runs the OctoBio firmware, which you flash once from the browser.
Sensors
| Sensor | Part | Value |
|---|---|---|
| Light | BH1750 | lux |
| Distance | Ultrasonic | cm |
| Temperature & humidity | DHT20 | °C, % |
| Motion | PIR | motion / no motion |
| Tilt | MPU6050 | 6-axis, no heading |
| Sound | Analog | raw 0 to 1023 |
| Soil moisture | Analog | raw 0 to 1023 |
| Knob | Potentiometer | raw 0 to 1023 |
| Button | Digital | pressed / released |
| IR remote | IR receiver | remote codes |
Outputs
| Output | Commands |
|---|---|
| Light D10 | on, off, flash |
| Light D8 | on, off |
| Servo | 0 to 180° |
| Relay | on, off |
| Buzzer | on, off |
| Screen | 16×2 LCD, two lines of text |
⚠️
Never connect the relay to mains voltage.
Limits to know
- Distance needs a facing surface. A missed echo is a negative number, not "very far".
- Sound, soil and knob are raw counts (0–1023), not calibrated units.
- Tilt has no compass heading.
- Focus and relax are uncalibrated indexes. Do not treat them as mood or a clinical score.