This is the second part of “What we do” this time about the IoT activities.
Our IoT effort can be roughly divided into two parts SW infrastructure and sensors. We use the standard IoT architecture combining an HUB and a cloud server. It is a typical IoT system setup allowing to collect the sensors information and control actuators over the Internet. The architecture uses an HUB. It serves as a gateway to the Internet and concentrator for the sensor data. The HUB is a simple computer with a similar power as a router equipped with Ethernet or WiFi or both to connect to the Internet. In addition, it may have several other radios for the sensor, actuator communication. The radios are continuously listening to sensors and this typically requires power, therefore, HUBs are usually not powered from a battery.
Our HUB is based on the Intel Edison dual core 500 Mhz Linux-based embedded computer with WiFi, BLE, and 868MHz free band radio. It also includes three USB sockets for additional peripherals. The HUB is running a simple Node JS server Zetta. This server is handling the management and communication with servers. It allows a seamless connection to similar Zetta server residing in the Cloud. The linked Zetta servers communicate using a walkable, JSON based, hypermedia Siren. The cloud-based servers allow a simple connection to the smartphone. The hypermedia Siren allows the smartphone to set the UI based on the configuration of a particular space covered by an HUB. We have designed and implemented an IoT control app for Android and it configures based on location. In practice, it means as soon as you get to a smart room or to your car the Android home page sets for the particular environment with the most frequently used control on top.
We do not use the WiFi for communicating with sensors. WiFi usually requires a lot of battery power and it is primarily designed for TCP/IP protocol, which may not be required for the very simple sensors such as thermometers. The thermometer is sampling the environment temperature for example only every 10 min and therefore we can let the sensor sleep most of the time. The radio is waking up only for the shortest possible communication required to exchange information with the HUB. This approach is allowing us to design sensors with very low energy requirements.
The low sensors consumption allowed us to use one of the energy harvesting approaches, the Photovoltaic Cells. We have designed and put together a set of PV powered battery-less and wireless sensors. We can measure temperature, humidity, motion (accelerometers and PIR). The PIR equipped sensor is powered just from a fluorescent tube on the ceiling and it is sensing people coming to our lab for more than one year. We are monitoring the PV accumulated energy and we have so far never run out of power. We use the accelerometer-equipped sensors to check for open windows. The outside light is also good enough to provide enough juice. The sensors communicate with the HUB using 868MHz radios. We have found this band more resistant to objects than the WiFi or Bluetooth. Currently, we use a proprietary protocol, but we are looking for LoRa and MQTT, which we use in other projects with the same HUB.
Some of the described work is part of the Bachelor’s thesis written by my students. We are looking forward to pushing our work even more ahead during eClub Summer Camp 2016.