The demand for wearable technologies steadily increased over all fields of application in the last years. Long battery runtime is one of the most wanted properties of wearable sensor systems. Requirements for wearable sensors differ from general purpose computing because of its low-power system design. To address this issue, an open source evaluation board was designed for the development of medical wearable sensors and algorithms.
ULPSEK was designed as a mother board to carry exchangeable sub-boards. The exchangeable modules are five vital parameter sensors, the microcontroller, the radio module and the power supply circuits (linear or switched). Sensors are available for electrocardiography (ECG), respiration, photoplethysmography (PPG), oxygen saturation (SpO2), skin temperature and acceleration. ULPSEK provides 17 terminals to measure the power consumption (measuring voltage and current) for different subsections of the system. Beside this, ULPSEK includes a low-power monochromatic graphic display, a speaker for acoustic signalling and a multicolour LED for optical signalling. All modules can be powered down by the microcontroller dynamically.
ULPSEK requires a power consumption of 585 µW (± 0.7) for continuous ECG recording at 200 samples per second (Sa/s), including QRS detection using Pan-Tompkins algorithm, heart rate and heart rate variability calculation. If activated by the microcontroller, the accelerometer requires additionally 17 µW (± 0.21) for motion detection, the temperature sensor requires 8 µW (± 0.1) and the PPG consumes 2418 µW (±4) for one channel data acquisition at 100 Sa/s.
ULPSEK is recommended for educational purposes and companies with interest in medical low-power sensor systems. The system is modular but also easy to use in default configuration. The large evaluation board is optimized for flexibility in development and accessibility to measure and identify unnecessary power dissipation. The evaluation kit is rounded up by its miniaturized and code compatible sensor belt.