Rezo Haptic Metronome

the question

I wanted to know whether a beat you feel on your wrist keeps people in time as well as a click you hear. To answer that I needed a device reliable enough to run a real study with, so I built one.

the hardware

Rezo runs on an nRF52840 on a custom PCB I designed in KiCad. Two linear resonant actuators, each driven by a DRV2605L haptic driver, deliver the pulse. The enclosure went through several revisions to make it comfortable for long sessions and keep the actuators in consistent contact with the skin.

the software

A phone app built with Expo and React Native controls tempo, tap tempo and vibration patterns over Bluetooth LE. A JUCE plugin (VST3/AU) syncs the wearable to a DAW's transport over MIDI clock, so it follows the session instead of running on its own clock.

the study

I designed and ran a 50-participant behavioral study on rhythmic motor timing. I defined the research question, conditions, outcome measures and inclusion criteria, then handled consent, recruitment, scheduling and the sessions themselves. I analyzed the timing data in R and Python.