At first sight the scene on the field covering several hundred square meters near Moers looks like an oversized light organ from the 70s. Look closer and you recognize the hot air balloons, their burners flaring up in time with the music, illuminating the outside of the balloons in twenty colors. The effect is old, but the technology behind it is brand new: The hot air balloons, some of which are more than a hundred meters away, are receiving their instructions via the new ZigBee wireless standard. Researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg have brought the huge light organ to life. Without ZigBee, they would have needed to connect a laptop to each individual balloon, involving several hundred meters of cable for the hot air balloon festival. The new standard enables signals to be sent wirelessly to the desired location via a network that keeps the data hopping from module to module until it reaches the right one. The ZigBee modules transport data in both directions, from a computer over the network to the programmed end module and vice versa. Each module is corresponding fitted with various components: a transceiver, microcontroller and various interfaces to connect sensors or actuators. The ZigBee protocol stack, which runs on the microcontroller, controls the network and is tailored to the customer's specific needs. The individual network modules can be up to 80 meters apart. The network can be programmed to both monitor and respond to inputs: temperature changes, humidity, vibration or gas emissions are detected by a local sensor module and sent from one module to the next until the data reaches the computer. Conversely, the computer can send commands to an actuator module that then executes these commands locally, as with the balloons. "Apart from range, the low energy consumption of the ZigBee network is one of the major advantages over other wireless standards. The modules are only activated if something happens", says Martin Lörcks from IMS. Otherwise, they return to an idle state.
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