C-Bus is a microprocessor-based control and management system for Buildings and Homes. It is used to control lighting and other electrical services such as pumps, Audio Visual Devices, Motors, etc. Whether simple ON/OFF control of a lighting circuit, or variable (analogue) type control, such as electronic dimmable fluorescent ballasts, C-Bus can be used to easily control virtually any type of electrical load.

The primary reasons to use C-Bus are:

• Highly robust and reliable control system, but low cost per node.
• Wide range of tools available to allow 3rd party companies to interface to both PC based and embedded systems.
• A single C-Bus cable connection can control an unlimited number of devices.
• Ultimate flexibility in switching and control – functions can be changed, added, removed, moved, reprogrammed, at any position on the network, at any time - without any cumbersome hard-wiring.
• C-Bus is simple to install and commission.
• C-Bus can control any type of load, digital and analogue.

C-Bus Network Wiring
The C-Bus Network Bus is the communications wiring for the system, consisting of an unshielded twisted pair (UTP) ‘Cat 5’ cable. The Bus not only provides the means of communication between units, but also the small amount of power needed to operate the circuitry within each C-Bus unit.

The C-Bus Network is electrically isolated from the mains power, and operates at safe extra low voltage levels (36 V dc). Legal restrictions of mains wiring do not apply, so C-Bus wiring may be run into places that would be dangerous (or illegal) with normal mains wiring.

All Input and Output devices are wired to any point in the C-Bus Network by a twisted pair cable, which carries all communications between the Units.

The C-Bus connections may be looped from unit to unit or a branch can be made at any point. This ‘free topology’ structure provides a flexible system layout. New units can be added anywhere, at any time, without re-configuration.

During commissioning, the system is programmed so that specific commands trigger specific responses in one (or more) devices on the Network. At any time the commands can be re-programmed, and C-Bus units can also be added, removed or moved.

The size of a C-Bus Network is practically unlimited. A large network is usually divided into sub-networks of 100 C-Bus Units, with a total cable length of 1000m per sub-network. This allows a C-Bus system to be divided into manageable sections, simplifying design, limiting potential fault propagation and aiding in any troubleshooting.

Example
In the diagrams and text below we give a very simple example of lighting in a boardroom



An Input Switch in the boardroom is programmed with the C-Bus Group Address ‘Boardroom Main Lights’. When the switch is pressed, it issues an ON Command to the ‘Boardroom Main Lights’ C-Bus Group Address.



This Group Address command from the Input Switch is sent onto the C-Bus Network for all units throughout the network. Only those C-Bus Units programmed to respond to the ‘Boardroom Main Lights’ Group Address command react– other units will ignore commands not intended for them.

This simple example only gives you an overview of the power and control flexibility of the C-Bus system.

As you can see from this simplified diagram, every device requires a C-Bus connection. Devices that control mains power also need a connection to the mains, of course. The mains wiring and C-Bus wiring do not need to be adjacent, and the mains can be connected to different phases, or even completely separate distribution systems.