"There is no RF technique covering all requirements," reports Fritz Jauss, R&D manager of home and building technologies at Honeywell, Germany. "Therefore, we have to carefully select the technology. The problem of Convergence is not the technology, the problem is costs." The appliance manufacturers are interested in RF modules that cost less than $5.
Look at the data traffic within a home-automation system for appliances. Short messages are sent out in 98% of all cases. Only 2% of the messages require faster data rates for uploading/downloading. Due to the fact that high data rates are always a tradeoff with sensitivity, range, and costs, it's a good decision to choose a low data-transmission rate for home automation to increase the system's sensitivity and range while keeping costs relatively low.
EHS uses the 868- to 870-MHz frequency band, with preferences for subbands at 868.7 and 869.2 MHz. Within one hour, the duty cycle may reach a maximum of 0.1%. This means that no device can transmit for more than 3.6 s per hour. Furthermore, devices have to stop transmitting at least after 0.725 s and pause sending data for at least 0.725 s. Frequency shift keying (FSK) modulation techniques seem to be the dominating transmission technique for the future in this application. Unfortunately, no dedicated RF semiconductor solutions for EHS are available or announced so far.
The first applications are about to start mass production now. Centrica, the owner of British Gas, will equip its gas heaters at over 7 million customers' locations with an EHS PLM. Another PLM will be installed close to the phone gateway for remote control and diagnosis of these heaters. The advantages are obvious. Only a minimum of installation is required, as the entire communication within the home takes places via the mains lines.
Load-Management System
Another example is the load-management system from BTicino, which uses powerline transmission between 125 and 140 kHz for communication. In Italy, the monthly basic fee for electric power significantly increases with the maximum peak power rate. So, most households voted for a maximum peak power rate of around 3 kW to keep costs low. Before now, blackouts often occurred when, say, the dishwasher and the washing machine were running simultaneously. The load-management system controls different energy-hungry appliances to prevent the load limiter from causing a blackout.
The system consists of a feature controller and up to 16 intelligent sockets. Each one is connected to a load that needs to be controlled. The feature controller can manage the available power coming from the utility and prevent the intervention of the energy meter thermal protection. It also can manage differentiated tariffs to save energy. The sequence for the load switching off is decided by the user, who sets the load priority with a selector positioned on the intelligent socket.
For more information about EHS, point your browser to www.ehsa.com. Also, check out sites like www.st.com, www.trialog.com, and www.bticino.it.