The three dimming protocols are typically available from all of the major lighting control companies and it’s becoming more usual for control units to be capable of providing a mix of all three protocols, either as a bespoke project fabrication or post-installation via the system programming.
Mains dimming is the oldest dimming protocol and is the type most likely to be seen in the home, as well as in shops, bars and restaurants. The system relies on reducing the voltage that reaches the LED fixture, typically by ‘chopping-out’ parts of the alternating voltage. Mains dimming was designed originally for filament lamps, when a simple voltage reduction meant a lower light output; it does not work naturally with the electronics of an LED driver, though manufacturers of LEDs have worked hard to come up with circuit designs that work sufficiently well. Lighting control manufacturers often incorporate mains dimming modules into their equipment.
DALI (Digital Addressable Lighting Interface) is generally used to provide area lighting control over a number of lighting circuits. It relies on an additional two-core cable connection between the dimmer control and the LED driver. It’s worth noting that there is a growing number of Dali-based dimming options for the domestic market. The LED driver is linked to a push-button controller (a retractive switch) at the wall, using a two-core cable. As there’s nothing clever in the control beyond a spring-loaded connector, there can be no problem with component compatibility; it’s all going on inside the driver. But it’s always wise to confirm the ability of the driver to provide those low lighting levels before committing to a specification.
DMX (Digital Multiplex) was developed originally for the entertainment world, where it’s used to provide dynamic lighting effects across very many lighting channels. In the architectural world, DMX works best for colour-changing and effects illumination, so there is a very close tie-in to LED performance. What the entertainment world knows very well and the general electrical installer may not know, is that the signal cables between the control unit and the LED driver needs to be a special data cable, properly screened to protect the cores from spurious electrical signals from adjacent cables.
Analogue dimming (0 - 10v signalling)
As the world turns to the benefits of digital its easy to forget that there is still a simple and reliable system of dimming available. Analogue dimming uses a DC signal (0 - 10v) between the control plate and the LED driver. As the signal voltage changes, so does the light output. Analogue dimming only works on a single channel basis, so a multi-circuit installation would require separate cables between each dimmer control and associated light fixture(s), whereas signal cabling for digital dimming can be provided by a 'daisy-chain' of signal cables to connect between fixtures with different addresses.
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