ESP32-Based Orbitrack Workout Computer

Dmitry Dziuba purchased an Orbitrack workout machine at the end of 2021. While it seems to be a usable device otherwise, he wasn’t pleased with its onboard computer, and so decided to build his own. The original display itself is monochrome with limited visibility, but perhaps more importantly, it only has sensors on the non-moving handlebars.

As it just so happens, Dziuba has been working the uECG project, a wireless heart rate monitor that straps just below one’s chest and is meant as something in between a prototyping platform and a medical device. As implemented here, the uECG acts as the hard rate monitor for the system, sending data to the ESP32 base unit over BLE. This base unit also senses rotary speed via a GPIO input, which is connected to th Orbitrek’s simple on/off revolution sensor.

With this data gathered, the base unit is able to output BPM, speed, distance, calories, and an ECG plot on its small color display. Training zones are calculated and displayed, with grey indicating that the user is below zone 1, blue means within zone 1, green, yellow, and red indicate 2, 3, and 4 respectively. Blinking red/purple indicates zone 5, which you don’t really want to cross into during training.

The display is a standard SPI model, which uses the Adafruit ST7735 driver library, so it should be fairly easy to use with different hardware as needed. The code itself is modular, and the speed input is a simple on/off contact, so it should be usable with other heart rate monitors and training machines. Code is available on GitHub, and a demo of the device in action can be seen below.