Lighting Control with KNX
The majority of mains KNX dimmers are electronic using a triac to chop the wave form reducing the power transmitted to the lamp and are universal, supporting both leading or trailing edge dimming. On a KNX dimmer the advised load limit refers to each individual channel, but it is often possible to join channels together to increase the load. Dimming of mains LEDs and compact fluorescents is supported however, it is important to check the advised rating of the dimmers as down rating is often required due to the inrush current. It is always advisable to test the characteristics of any given lamp/dimmer combination.
Commonly used with LED or fluorescent lamps, 1-10v dimming requires a separate control cable linked to each driver along with the standard mains cable. Because the dimming signal is separate from the power supply and the driver is controlling the output, a more consistent light output is possible across the full range of dimming. A separate relay is required to turn the fitting off and all KNX 1-10v dimmers have this integrated.
DALI (Digital Addressable Lighting Interface) works in a similar way to 1-10v as a separate control cable is required along with the mains feed to the fitting or driver. However, each driver is assigned an address allowing circuits to be regrouped depending on the room requirements. Used extensively in commercial environments, especially where emergency fittings are required, DALI also provides a flexible solution for residential projects, particularly when a high quality of dimming is required. Depending on the configuration, it is possible to get the status of each individual lamp or driver including faults. With a limit of 64 addresses per DALI universe KNX provides a scalable backbone to link individual DALI universes together.
KNX LED Drivers
KNX LED drivers are available which allow control of a LED fitting directly from KNX. Primarily designed for colour control of LED strip lights, the drivers can also be used for single colours or LED spotlights. As with most LED drivers a separate power supply is required but with both constant current and constant voltage models available, a wide range of LED types can be controlled. This is the most direct and simplest method to control LEDs in a KNX installation particularly if colour changing is required.
DMX is a protocol founded in the theatre lighting industry and is often specified when a large amount of colour changing fittings need to be controlled simultaneously. It is sometimes used in gardens, home cinemas or pool areas but DALI, 1-10v or direct KNX drivers offer the same benefits in a simpler format. A DMX controller is required to control the fittings which can take the form of a DMX keypad, lighintg control desk or a KNX gateway.