Simband operation modes
Simband has four modes of operation. We defined each mode to address a different need for data collection, while also addressing functionality and battery life. Each mode defines which sensors will be activated and when and what data will be collected. The transition from one operation mode to another is determined by context and user input.
As the name suggests, this mode in Simband is used for monitoring of signals. Monitoring mode is activated when the Monitor application is launched. During this time, all sensors on Simsense are running and collecting data. Simsense sends all data it gets from the sensors to the base, making it available for algorithm consumption on the base. During Monitoring mode, the only algorithm that runs regularly on Simsense is the sample-rate converter, which normalizes the different streams to the same clock and to a 128 Hz sampling rate.
Though Monitoring mode gives us full flexibility, it consumes a lot of power, as it requires all the sensors and all the processor to be ON and functioning. This is not feasible in a system that works 24 hours. Collection mode is activated when no Simband application is running. During this time, Simsense silently turns on one PPG channel for 10 seconds every 2 minutes, collects data and extracts heart rate (with an attached confidence indication). Once every 45 minutes, based on power and memory considerations, Simband will wake up, flush that data from Simsense and make it available on Simband, and eventually on ARTIK Cloud. Along with HR, Skin temperature, Motion Flag, GSR Tonic, HeartBeats, and PPG confidence indicators are also collected.
Continuous collection mode
Though Collection mode collects lot of information while expanding system runtime by conserving power, there are a few applications which would appreciate even more detailed information. When Continuous collection mode is enabled, Simband continuously collects HeartBeats, PPG confidence indicators and Motion Flag. Meanwhile, all other parameters of Collection mode are collected every two minutes. This mode can be enabled / disabled from Simband settings > Flags > Continuous collection mode.
Fitness mode is geared toward fitness and activity. Simband will transition into Fitness mode whenever Simband detects any physical activity (e.g., walking or running) or when heart rate (HR) > 110 (configurable). This mode can be explicitly turned on by activating the Fitness application. All Simband sensors are activated to collect data in this mode, just like in Monitor mode.
With Simband being a research platform, we have given special importance to battery performance from Day 1. Starting from 6 hours of battery life, we have increased the number to 30—and we are still to improve from here. At this time, while in Monitoring mode (where all the sensors, algorithms, screen and WiFi are running), power consumption is very high.
The Simband charger has an LED whose different colors and blinking patterns are explained in the diagram below: