C-Bus is a home and building automation protocol that is used in Australia, New Zealand, Asia, the Middle East, Russia, USA, South Africa, the UK and other parts of Europe including Greece and Romania.

It is used in the control of domotics, or home automation systems, as well as commercial building lighting control systems.

Although the most common protocol is X10. C-Bus' works completely different to X10 and is a professional automation system that you cannot compare to X10. (X10 is soley used for domestic and is good for small projects.) C-Bus was created by Clipsal's Clipsal Integrated Systems division for use with its brand of home automation and building lighting control system. C-Bus has recently become available in the USA under the 'SquareD Clipsal' brand name.

C-Bus System

The C-Bus System can be used to control lighting and other electrical systems and products via remote control and can also be interfaced to a home security system, AV products or other electrical items. The C-Bus system is available in a wired version and a wireless version. There is a gateway to allow messages to be sent between wired and wireless networks.

The wired C-Bus system uses a standard category 5 UTP (Unshielded Twisted Pair) cable as its network communications cable. The category 5 C-Bus network wiring uses a free topology architecture. The maximum length of cable used on a C-Bus network is 1000 metres; however this is easily extended using C-Bus Network Bridges. Up to 100 units can be installed on a C-Bus network and this can also be extended using Network Bridges.

The maximum number of C-Bus networks in one installation is 255 (note that this limitation does not apply if a C-Bus Ethernet Interface is utilised, the system size is then limited to IP Addressing only). The maximum number of networks connected in series to the local network via Network Bridges is seven (i.e. using six network bridges).

Each standard C-Bus unit requires 18mA @ 36Vdc to operate. However some C-Bus units require up to 40mA.

More than one C-Bus power supply can be connected to a C-Bus network to provide sufficient power to the C-Bus units, the C-Bus power supplies will share the load evenly.

Each C-Bus network requires a network burden. This network burden is software selectable on C-Bus output units.

Each C-Bus network requires at least one system clock generating unit for data synchronisation.

The isolation between the mains supply circuitry and the 36V dc C-Bus circuitry is greater than 3.5kV. This is achieved using double wound transformers and opto isolators. This means the C-Bus wiring, connections and circuitry can be considered Extra Low Voltage.

C-Bus Protocol

C-Bus is an open protocol which enables any manufacturer to interface to other C-Bus devices. The protocol is made available via the C-Bus Enabled Program, however licensing is necessary.

The future of C-Bus

C-Bus as a home automation and building lighting control system is used primarily in Australia (Sydney Opera House etc.). C-Bus is currently available in Asia (thousands of installations), the United Kingdom (installed in Wembley Stadium), Russia (huge success on countryhouse market), USA (named SquareD) and a number of other countries are now using this system. One major obstacle to widespread use of wired C-Bus is that it will not work with a standard mains wire installation, a completely new wiring system must be installed for a wired C-Bus system which means that it is normally only used for new builds. The C-Bus wireless (RF) system can however be retrofitted using the existing mains wiring.

C-Bus is compatible with TCP/IP, Crestron, AMX, LonWorks, ModBus, Charmed Quark Controller and some other protocols through interfaces.

External links

• cbusforums.com — A community for users of C-Bus.
• C-Bus Enabled Program — Program for accessing the C-Bus protocol.
• CIS Software Downloads — Free software for programming and communicating via C-Bus.
• CIS Technical Support — Technical information and support services for C-Bus products.

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