電車ベクトル (DenshaBekutoru)

Model Train Direction Sensor

DenshaBekutoru is a small controller board for brick-built model locomotives.

The target use case is: read the motor power signals, detect the current driving direction, and switch the headlights accordingly. The software is also prepared to derive speed information from the motor signal behaviour.

This project is built around one practical problem: the motor is driven from an H-bridge, so the signal is noisy, polarity changes are not “clean logic”, and inductive spikes make direct evaluation difficult.

What it does

detects train direction from the motor power signal
evaluates two processed motor-side signals via analogue inputs
switches the front / rear lights according to direction
keeps the last valid direction if the train stops or the signal becomes unclear
is designed as small as possible for installation in brick-built locomotives

Technical approach

The current version is built around:

optocoupler-based input isolation and signal conditioning
Arduino Pro Mini 5V as controller
software averaging of analogue inputs
startup calibration to adapt to different controllers and builds
threshold + hysteresis logic
simple state machine with direction memory
PWM-capable output pins for possible later LED dimming

The main idea is not to read one raw signal and react immediately.
The idea is to turn a noisy motor signal into a stable direction decision.

Current status

Version 2 (beta) is built and working.

Current state:

schematic finished
PCB finished
firmware finished for the current beta state
three PCBs built and tested
first boards handed over for real-life testing in a model railway club
Feedback and what to improve

Design goals

as small as possible
beginner-friendly where possible
no SMD if it can reasonably be avoided
easy to reproduce later as a DIY kit
modular PCB concept with main section, future-option section, and test section

Repository content

Typical content of this repository:

KiCad/ – schematic and PCB files
firmware/ – Arduino test and controller software
documentation and pictures will be added step by step

Project status note

This is still a beta project.

The current hardware and software already work, but testing on real locomotives is still ongoing.
The next version will depend on real-life feedback from actual use.

Possible next steps:

verify behaviour with different motor controllers
check robustness in real train builds
improve wiring / connector handling
finalise optional features like LED dimming
prepare a first “official” DIY kit version

Blog / documentation

Project overview: https://togo-lab.io/?p=223
Hardware description: https://togo-lab.io/?p=233
Software description: https://togo-lab.io/?p=243

Short summary

DenshaBekutoru is a small Arduino-based direction sensor for brick-built model trains.

It reads the noisy motor signal from an H-bridge-driven setup, isolates and evaluates it, and switches the headlights automatically.

The current beta version is working and now entering real-life testing.

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