Please note: the JRF no longer conducts any research into this area of work. The information provided in this section is kept here for historical purposes.
How does it work?
Taking decisions away from mechanical switches
The majority of commands in current homes are passed on to the device in question through the use of a physically operated switch. Generally pressing a switch or turning a dial directly alters the supply of electricity to a device. The switch or knob opens or closes an electrical connection or varies the resistance of that connection. The diagram below illustrates this using the example of a typical lighting circuit. The lights in the circuit are linked into a separate switch that is able to interrupt the flow of electricity to the light fittings.
In the smart home the switch takes on a different function. Rather than regulating the flow of electricity, the switch merely sends a signal to a communication network, called a bus system, informing the network of the new position of the switch. A controller fitted to a single light fitting, or a number of light fittings, receives this signal, recognises that the message is intended for it and responds, in this example by turning on the light. The regulation of electrical flow takes place at the controller rather than at the switch.
The example of controlling light fittings gives little added utility to conventional methods of control. Flicking a light switch turns the light on or off as appropriate. However, if the bus system connects more than just lights, it is possible to radically change the the way the home is controlled. The switch is no longer directly related to any particular device so it can operate any device on the network that has been told to respond to the signal from the switch. So multiple lights, possibly in different rooms, could be controlled and even dimmed to different levels. The diagram below illustrated this.
Devices in the home are now able to change status in response to a signal on a network and so commands no longer need to come from a physical switch - or a variety of devices could react to the same switch. Other pieces of equipment connected to the network are able to send messages that may tell a device to turn on or off. The lounge lights can be programmed to response to a light level sensor signalling that it has gone dark and a movement detector saying that there is someone in the lounge.
Networked control around the home extends beyond the relatively simple activities of turning lights on and off but this has been used as an example of how the system works. With a wide variety of devices connected to the network, previously discrete systems are able to share resources and information and to response more appropriately to external stimuli.
Passing information around the home
Smart homes rely on the ability to distribute information and commands around the home as described above. There are a variety of ways that this can be achieved. Broadly these can divided into wired or wireless methods. Wireless communication involves a more emergent set of technologies that have great potential but little demonstration usage in smart homes.
Dedicated wiring bus
A wiring bus is a dedicated wiring system installed purely for the purposes of distributing information. Typically a communications bus will rely on an unshielded twisted pair cable (UTP), which is a cable with at least two separate wires insulated from each other but without any sheathing to prevent interference from radio waves. The most common form in an existing home is the telephone cabling. In the smart home a better quality of cable than this is required and usually category 5 (Cat 5) network cabling, which is used for computer networks in modern offices, or similar will be specified. Cat 5 cabling consists of four pairs of cables, potentially allowing four sets of signals to be sent over the same cable.
Linkpower
In the homes developed by the JRF a variant on the wiring bus is also used called linkpower, where a twisted pair is used for communication and low voltage dc power to devices.
Powerline communication
Powerline is the use of the existing power network to carry data signals in addition to the 240V supply. Powerline communication can be a very effective medium for installations in existing homes as it can require very little rewiring. Powerline is limited to a relatively narrow bandwidth as a result of UK legal regulation of the usable frequencies. This limited bandwidth makes it more useful for relatively simple message, such an on, off or dim, rather than more complex signals, such as video transmission.
Infrared communication
The use of infrared transmitters and receivers in the home is already fairly common. Remote control units for audio-visual equipment almost exclusively use infrared to communicate with their appliances. Infrared can also be used for command and communication purposes in the smart home. Very few systems have been developed in practice, however, as a clear line of sight between transmitter and receiver is required. Infrared remote controls, particularly those that can learn signals and be programmed with new function, have been used extensively by JRF in its smart homes as a method for sending command signals to the main network.
Radio frequency communication
An emergent medium for smart homes is the use of radio signals to communicate. New standards developed initially for computers are now starting to be applied to smart homes. LAN, the IEEE 802.11b standard for wireless computer networking, and Bluetooth, a standard for short range wireless communication for computers, peripherals and mobile telephone, have both been suggested as new mediums for smart homes communications.
Different smart homes protocols
As well as a variety of mediums for passing information around the home there are also a variety of communications protocols for operating smart homes. In the UK at the time of writing these protocols allow little if any interoperability between them.
LonWorks
The American Echelon Corporation's LonWorks protocol was originally developed for commercial buildings and industrial processes. LonWorks is capable of being used over all communications mediums but is most commonly installed as a dedicated bus or powerline system. Echelon licenses its technologies to a large number of manufacturers giving a wide product base for home installations.
Konnex
Konnex is the result of the convergence of a number of previously separate European standards for communication. It consolidates the protocols of the European Installation Bus Association (EIBA), BatiBus Club International (BCI), and the European Home Systems Association (EHSA). Again Konnex is suitable for use over all mediums and by the nature of the merger of previous consortia has a wide manufacturing and product base.
X-10
X-10, developed in the US in 1977, is a simple, low cost protocol for powerline communication. Compared with LonWorks and Konnex it is limited in terms of scope with a maximum of 256 devices available to be connected to a network.
Bespoke protocols
Various manufacturers have also developed their own communication protocols for use in homes. These tend to be limited to the interoperability of their own equipment and so are not covered in any detail on this site.
Controlling smart homes
The interface between the smart home and the user is vital to ensure that the home is easy to understand and operate. Below are descriptions of the most common interfaces used to control the smart home.
Physical switches
The normal switches and dials used in the home may be suitable for controlling aspects of the smart home. JRF has made extensive use of the existing switches by wiring them to the powerline network in a slightly different manner. This was done to ensure that the home is accessible to anyone who uses it. If a dedicated bus system or a wireless network is used, conventional switches may need to be replaced with ones that are specific to that form of communication.
Infrared remote controls
As discussed earlier, infrared can be used as a communications medium for the whole of the network or elements of it. Infrared can also be used as a way of sending signals to the network. If infrared receivers are linked into the communication network, remote control units similar to those used for consumer electronics products can be used as an interface with devices on the network. JRF have used a variety of 'learning' remote controls, which can have their buttons programmed to emit a specific signal or series of signals, as the main interface for users inside the home.
Computers
While many smart homes rely on distributed control systems that don't need a personal computer to operate, computers can be used as an interface with the home. Computer screens allow large, easy to recognise visual representations of the home and can be used to send messages to, and receive messages from, the smart home
Internet
The addition of a web server to the home would allow a visual representation of the home to be created as a web page and accessed from a web browser. This could be used to control the home either from inside over a local area network (LAN), or remotely, if an internet connection was always on in the home.
Telephony
The connection of the network to a telephone line through the use of a modem allows a variety of telephone control options for the home.
Tone
dialling
Conventional telephones inside the home can be used as interfaces
with other devices. For example, they can be linked to a door entry
phone to answer and permit entry. The house could also be dialled
into from outside and commands given using tone-dialling signals.
WAP
The wireless application protocol (WAP) allows mobile telephones to
link to a limited version of the internet. Equipping the home with a
WAP server would allow control via a mobile phone.
Bespoke panels
A number of manufacturers produce panels that can be used as interfaces with the smart home. These can range from simple switches with a display panel to confirm status to more complex panels that can operate a range of devices.
Voice
Recent developments in speech recognition technologies are making the possibility of using spoken commands to operate the home more likely. Current microphones would need to be positioned close to the user's mouth to eliminate background interference but more centrally located microphones may be possible in the near future.