Bx tacho

BX Tacho

English | 繁體中文

An open, DIY launch RPM meter for Beyblade X launchers. It clips onto the back of the launcher, reads the launcher's spinning black/white pattern with an IR sensor, and shows the launch RPM on a small OLED.

Web app: dazchi.github.io/bx-tacho (Chrome or Edge on a computer, Chrome on Android)

What it does

• Measures launch RPM optically, up to about 20,000 RPM, and shows the result and the peak on the display.
• Senses when a Bey is loaded and when it's released, so each shot is recorded automatically: no buttons to press.
• Keeps a shot history: the last 50 shots, the total count, the best shot and the latest launch curve.
• Bluetooth: uses the Bey Battle Pass protocol, so Battle Pass apps can read your shots.
• Runs on a 1S LiPo with USB-C charging, a power switch, battery monitoring, and sleep when idle.
• Left-handed mode: the display can be turned 180°.

Web app

The web app runs in the browser, with nothing to install:

• Bluetooth: live shot data, battery, the launch curve and your history.
• Firmware updates over USB or Bluetooth, with one click for the latest release.
• A console over USB or Bluetooth, for settings, calibration and diagnostics.

It's available in English, 繁體中文, 简体中文 and 日本語. Details: web/README.md.

Hardware

An ESP32-C3 (ESP32-C3-WROOM-02) with two ITR8307 reflective IR sensors:

• one reads the RPM, through an LMV331 comparator;
• one detects a loaded Bey.

The rest of the board:

• a 0.96″ SSD1315 OLED;
• a TP4054 charger, with load sharing so it runs while charging;
• USB-C for power and data.

• hardware/: KiCad 10 project (schematic, PCB, footprints, 3D models). Gerbers and the BOM for JLCPCB assembly are in the hardware v1.0 release.
• mechanical/: STL files for the 3D-printed case: case_top, case_bottom and the launcher clip.

Firmware

ESP-IDF v6.1 firmware in firmware/.

Installing it: use the web app's update button, or download the firmware from Releases. Your settings and shot history are kept.

Building it yourself:

cd firmware
idf.py build
idf.py -p COMx flash monitor

Build options, the console commands, calibration and the Bluetooth protocols are covered in firmware/README.md.

License

GPL-3.0-or-later. Copyright © 2026 Darren Chi (github.com/dazchi). See NOTICE for the exception covering the optional firmware extension.