- An open model train car of type Nd (you may use basically any other car that fits you needs).
- Single-cell LiPol battery (500 mAh, 3.7 V).
- Axis with perforated wheel.
- GP1S23 opto sensor.
- Main PCB connected to sensor & battery.
- Bluetooth module HC-05 connected to main PCB.
- Use fixed coupling, the measured data will be much clearer.