Hardware Components
Overview of the Data Walker hardware components and their specifications.
Core Components
ESP32 Development Board
The brain of the Data Walker. We use the ESP32-WROOM-32 module with:
- Dual-core 240 MHz processor
- 4MB Flash memory
- Built-in WiFi and Bluetooth (future features)
- USB-C connectivity for programming and charging
Hall Effect Sensor
A latching Hall effect sensor detects magnets as the wheel rotates:
- Model: SS41 or equivalent latching sensor
- Detection range: up to 10mm from magnet
- Operating voltage: 3.3V
- Output: Digital high/low on each magnet pass
Wheel Magnets
Three evenly-spaced magnets are attached to the wheel:
- Type: 6mm × 3mm neodymium disc magnets
- Quantity: 3 per wheel
- Spacing: 120° apart for balanced detection
- Mounting: Adhesive or recessed into wheel spoke
Why 3 Magnets?
Using 3 magnets provides better resolution and allows the self-test to verify even spacing. This catches issues like loose magnets before they affect measurements.
Display
A 1.3" OLED display shows real-time distance and menu options:
- Resolution: 128×64 pixels
- Interface: I2C
- High contrast for outdoor visibility
- Low power consumption
Enclosure
The 3D-printed enclosure protects components and mounts to the walker:
- Material: PETG or ABS for durability
- Mounting: Clip-on design for standard walker frames
- Access: USB port accessible for charging/programming
Connections
The Hall sensor connects to the main unit via an RJ22 (4P4C) cable:
- Pin 1: VCC (3.3V)
- Pin 2: Signal
- Pin 3: Not connected
- Pin 4: GND