The nightlight itself contains a variety of sensors, as well as the RGB-leds for creating lights, built around Arduino-FIO. Some I/O-pins are used directly as a single-slope integrators when measuring capacitance with the embroidered conductive yarns, to detect touch-related events, such as the stroking or when the light is being held. ADXL337 accelerometer is used for the measurement of the changes in movement, however, when combining with the touch-detection, the context is easier to detect. Force-sensitive resistors are used for the detection of the squeezing, and a generic electret microphone with an amplifier is used for the FFT input. There are two communication modules, ESP8266 for the wifi, and RN42XV Class 2 Bluetooth-module for direct communication with the tablet application.
The nightlight communicates with the Orion Context Broker using RESTful api. Orion Context broker is a publish/subscribe context broker from FI-WARE cloud, and can be used to keep track and store real-time sensor data over the internet. It also serves as a data storage for the events of the previous nights. We set up and maintained the context broker ourself.
The nightlight has two working modes: storybook and sleeping. In the storybook-mode, it communicates with the tablet application to update information for the story, such as the detected strokes, squeezes and speech patterns. The tablet responds by sending control-information for the lights, according to the story. In the sleeping-mode, the nightlight updates the data directly to the context broker, making it available for the parents, as well as to use the child’s nighttime behavior as a basis for the oncoming story. The storybook application has been written with processing.