Acquiring unobtrusive sleep-related signals through an ESP32-based data logger

The problem of sleep occurs in all ages. Sleep deprivation causes impairment in immune systems which results in unfit, indistinct representation or an occurrence of brain and cardiac pathologies. Polysomnography is normally used to record sleep-related signals. However, the polysomnography is obtrusive, cumbersome, and expensive. Therefore, we aim to design and develop a data-logger for recording five sleep-related signals: electrocardiogram, photoplethysmogram, body temperature, body movements, and ambient sound. We created an efficient firmware to acquire such signals based on the low-cost ESP32 microcontroller. We designed 2 main tasks facilitating by the dual-core processors inside the ESP32 which can manage and store all recorded data to an SD card simultanously. We conducted experiments with ten subjects to evaluate our device with three vital sign parameters: heart rate, SpO2, and body temperature. The results show that the average percentage error of the three parameters compared to those of the standard patient monitor is less than 5%. This proves that our device can be used for further laboratory experiments with recorded data provided for analyzing sleep quality.