Armin Anders Head of Marketing EnOcean GmbH, Germany
Which radio system is best suited for automation of building services?
This is a question that is increasingly being asked by system integration and power system design engineers, and even by architects and home builders. There are many aspects to consider, and the final decision is further complicated by the large number of similar systems on the market, each with different operating parameters. This article is devoted to the selection of radio technologies and an examination of the most important operating parameters. What are the key factors to pay special attention to?
Systematic analysis of individual requirements related to performance, cost and flexibility of the desired radio system quickly narrows the possible choices. Let's look at the decision-making process in more detail.
Decision 1:
Large or small data volume?
Do you need to transmit animated images over the radio, use wireless connections between computers, or transfer images to a printer? If so, you need a radio system with a high data rate, which can transmit large amounts of data in short periods of time. This can be achieved using WLAN or Bluetooth radio standards – but these modes require a lot of energy to operate. This means that these modes are not suitable for applications where the device must operate for long periods of time on batteries.
However, most functions used to automatically control building systems require the transmission of only small packets of information over radio for short periods of time. This category includes switching on and off lighting systems and other equipment, controlling blinds and shutters, and especially the transmission of information from radio sensors such as climate control sensors, motion sensors, smoke detectors, etc. If you need to use such devices, you will need to make the following choices to further narrow down the range of technologies that can be used in your case.
Decision 2:
What are the environmental conditions?
This is a key issue in ensuring reliable data transmission over a radio channel. Signals sent simultaneously by radio from several transmitters located close to the receiver will interfere with each other, and therefore reliable reception of data by the receiver in such conditions is quite difficult. This does not pose a serious problem in a detached cottage, since the radio channel is used by a relatively small number of radio transmitters and receivers of radio signals, and this almost never leads to its overload. Proprietary battery-powered radio systems offered by various manufacturers of such equipment work quite well in such cases, despite the fact that they have a relatively low data rate, which can lead to interference of the signals they send. However, the situation is very different in larger buildings. In them, a large number of radio components can be located in a relatively confined space. For this reason, it is very important in such cases to choose radio systems that can cope with the problem of interference. A cheap method of preventing unnecessary overlapping of transmitted information packets is to use very short radio pulses by increasing the data rate. For this purpose, you can use ZigBee radio systems.
Solution 3:
Do the batteries need to be replaced?
If the need for maintenance, which consists of replacing batteries in radio sensors and radio switches, is a disadvantage, then it is possible to find radio systems without batteries. EnOcean GmbH is currently the sole copyright holder for the technologies used in such systems. These technologies were developed based on extensive practical experience with existing radio systems. Let us consider the specific features of such radio systems in more detail.
Power consumption
This radio protocol requires only 0.12 µW*s of power to reliably transmit 1 bit of data over a distance of 300 m (in open space). EnOcean radio switches require only 50 µW*s of power for a complete radio command. Both of these values are very low – approximately 100 times lower than standard battery-powered radio switches. This fact is the basis for creating wireless sensors that operate on energy obtained from the environment: from a single press of a button, from light energy captured by small solar batteries, or from a temperature difference of only 3o K. Even these small amounts of energy are enough to operate equipment that does not require any additional maintenance.
Reliability of data transmission
Very short messages (one switching command lasts only 0.5 milliseconds) and an intelligent strategy of repeating all transmission elements several times provide EnOcean devices with excellent immunity to interference, also providing protection against sporadic and periodic radio interference. Thus, more than 99.9% of the signals sent by 500 EnOcean transmitters installed close to each other and switched on once per minute are eventually actually received by the receiver.
Scalability and radio system topologies
The EnOcean message structure is very flexible. It can be extended to include complex data structures, large data volumes, encryption procedures, modulation methods and frequency bands used. In addition to unidirectional switches and sensors, bidirectional EnOcean modules can be used to support more complex radio topologies, including intelligent sensor systems such as radial and mesh networks.
Interoperability
The ever-expanding user base of EnOcean radio technology has already resulted in a wide range of compatible radio components. This means that products from different manufacturers can communicate with each other via a radio interface. For example, signals from radio switches from PEHA, Bticino and Omnio or room thermostats from Thermokon can be received and processed by receivers from WAGO, Beckhoff, Wieland, Phoenix Contact and Zumtobel, as they are compatible with the bus systems used in them.
Conclusions
No single radio system can meet all the different requirements equally well. The WLAN and Bluetooth radio standards are well suited for applications in which large amounts of data must be transmitted. Control of the operation of engineering systems in buildings and the transmission of data from sensors opens the field for the use of wireless sensors and switches, but in many buildings it is not always possible to use devices that operate on batteries and therefore require periodic maintenance. In these cases, it is possible to create maintenance-free systems based on the “EnOcean” radio technology. Such systems can be created even in large buildings with a large number of installed radio devices.
Based on materials from the AutomatedBuildings website |
