Precision monitoring of temperature, humidity or air pressure is crucial to museums, libraries and archives and in future this will involve less costs and zero maintenance. For researchers in Freiburg have developed the first battery-free Internet sensor, powered via a special solar cell for indoor use, enabling tens of thousands of connected mini sensors to transmit measurement values directly to the Internet via WLAN or GSM.
There is no need for a base station either - data can be logged via the Internet and alarm messages sent to designated persons automatically via e-mail or SMS. The research group, which is led by Dr. Tolgay Ungan, will be presenting the sensor for the first time this week. The newly founded endiio GmbH is a spin-off from the Department of Microsystems Engineering at the University of Freiburg, Germany.
Tens of thousands of mini sensors awoken as required
The Internet sensor uses patented wake-up wireless technology, which rouses tens of thousands of sleeping mini-sensors so they can collect measurement data. This makes the system 10,000 times more energy efficient than conventional wireless solutions. Both the Internet sensor and the mini sensors are supplied with energy from the interior-use solar cell and can even be operated in poor light conditions. A minimum of 50 Lux is required but, with an ambient light less than 50 Lux, several decades of operating time can be ensured using an integrated energy buffer.
Simplicity meets economy
As well as no additional costs for a base station or spare batteries, a further new feature is the use of special coatings on the solar cell, which enable the colour of the components to be adapted to the exhibition rooms. The monitoring system uses latest-generation multisensors by Bosch Sensortec GmbH, which require no recalibration, opening up new possibilities for low-cost, zero-maintenance monitoring of climatic conditions in museums. The gas sensors can even be used to monitor visitor flows.
"We held intensive discussions about use of the sensors in practice with the Deutsches Museum," explains Tolgay Ungan. Requirements cited by experts in these discussions have already been incorporated during its development.
At the Institute for Microsystems Technology at the University of Freiburg, research has been conducted on what are known as "energy-harvesting technologies" for a long time now. The goal of this is to enable microsystems to operate self-sufficiently without use of any batteries so they can be supplied with energy from the environment, thereby recording sensor values and transmitting these wirelessly. To date microsystems of this type could be developed where energy was supplied from mechanical motion, temperature differences (Peltier effect), light (solar cells) or even blood sugar (fuel cells) but such systems were only able to transmit a radio signal to a permanently available base station once power had been accumulated for a very long time.
Source and top image: endiio GmbH