Characteristics of a home automation system
A home automation system is based on three technical concepts:
The architecture of a home automation system specifies how the various elements of the control system interconnect. Here one can find two fundamental architectures:
- Centralized architecture – This architecture is characterized by having a central element, through which all the information passes. This type of architecture is usually more economical because it removes the ability to process from the various devices and centralizes everything in a single device.
- Decentralized architecture – Does not require a central element. Thus, it is much more flexible and less susceptible to failure, since the failure of one element only compromises the functioning of that same element. This is the architecture adopted by the main home automation protocols available, including the X-10 and KNX.
The means of transmission is the physical support in which the information exchanged between the various devices of the home automation network circulates. Usually, each home automation system supports several means of communication, using gateways to connect them with each other.
The main means of data transmission are: metal wiring, electricity network, optic fiber, infrared and radio frequency.
Metal wiring transmission
It uses its own metal wiring as a means for transmitting control signals (and sometimes for module feeding and voice signals transmission). This means of transmission is mainly used in telephone networks, in the distribution of audio/video signals, high fidelity audio and data. Twisted copper pairs are usually used (Ethernet networks or EIB bus), but coaxial cables that allow higher transmission speeds can also be used. The main advantages we can highlight are the great reliability and a good transmission speed. However, this type of transmission implies great implementation costs, especially in houses already built.
In the case of metal wiring as a physical means of communication, it must be taken into account the network topology. The topology can have several shapes: bus, star, ring, tree or mesh.
Electricity network transmission
It uses the electricity network that already exists in the house. Through the insertion of high-frequencies we can modulate signals in the current electricity network without interfering with the usual electrical appliances. The advantage of this type of transmission is the low installation cost, and the fact that it can be easily used in homes already built. Its biggest disadvantage is the low speed of transmission associated with a reduced reliability.
This is the main means of transmission used in the X-10 systems.
Optic fibre transmission
It uses a combination of semiconductors and optic fibre technologies. The optic fibre is a means of transmission that presents a high reliability of data transference and immunity to electromagnetic interference. It presents high-speed transmissions associated with a high cost of cables, connections and equipment. This means of transmission is not very used in the current home automation systems.
Nowadays, the infrared transmission is extremely common in audio and video equipments. Its application is very convenient and flexible and presents great immunity to electromagnetic interference. Its main disadvantage is the need of "being in sight" between the transmitter and receiver.
Radio frequency transmission
The radio frequency transmissions remote control is much more flexible, since the signal goes through walls and other obstacles. This type of transmission is very susceptible to electromagnetic interference and has a very low transmission speed. It is usually used in remote controls that require high mobility.
In order for two devices to communicate, it is not only necessary to interconnected them through a means of communication, but also that both speak the same language and use the same communication protocol. The protocol specifies the message format, the common language to all devices so they can understand one another. Among the existing protocols, the following distinction is made:
- Standardized protocols –These protocols are opened to any company, thus ensuring the future of technology and the existence of a huge variety of products from different manufacturers, who communicate and interact with each other.
- Proprietary protocols –Are the ones developed by one company and that company alone or other licensed companies that manufacture products capable to communicate with each other. The bet on these solutions implies a huge risk, because if the company decides to stop betting on this technology, the customer is left without a guaranteed support and without the possibility to expand the system.
The use of open protocols is highly recommended
, thus guaranteeing a better support, which is does not depend on a single company, and a larger product portfolio.