AMX RE-DM4, RE-DM6 manual Appendix a AMX Lighting Curves

Appendix A: AMX Lighting Curves

Appendix A: AMX Lighting Curves

Overview

Thousands of different lighting fixtures with unique shapes and styles exist, all designed to do something visibly different with light. Any one of those fixtures in a hundred different locations could produce a different lighting effect. Two identical lights in different locations could produce different reflections and shadows.

For instance, consider a situation where low-voltage track lights are mixed with compact fluorescent down lights to illuminate a hallway with pictures. Under normal dimming conditions, the two different light sources would dim differently and possibly require individually set dimmers to accomplish uniform lighting at different levels. An Up or Down button on a wall control panel would dim both sources at a common rate, but the lamps and fixtures would dim at different rates due to the lamp and ballast characteristics. The track light may stay bright for an extended period and then rapidly dim to nothing while the fluorescent lamp dims smoothly to a point and then abruptly shuts off. The combined effect produces an uncoordinated scene change.

An unwanted feature of dimmable fluorescent ballasts and low-voltage electronic transformers is their tendency to cause the lamps to flicker when dimmed to low levels. The normal way to avoid this is to use presets that are not dimmed below the fixture's threshold or to use any low end trim feature provided by the ballast or transformer manufacturer. Problems arise when the performance of the dimmer does not match the performance of the dimmable ballast. The AMX Lighting system now gives the user the ability to change the performance of the dimmer to avoid problems.

Many types of track lights and dimmable ballast only have a limited dimming range for the dimmer to work with. In a dimming range of 0 to 120 volts AC, many lamps do not start to dim until fewer than 100 volts is applied. Lamps often do most of their dimming between 40 and 100 volts. Dimmers designed to increment voltages from 0 to 120 volts can be wasted on lamps that do not even respond to 50% of the dimmer's output. Some lamps are more sensitive to voltage changes at the low end and can accommodate many degrees of dimming, but standard dimmers tend to rush past the lamp's sensitive range and occasionally linger in an unusable range.

Slowly turning a lamp on can be a very different effect than slowly dimming that same lamp off. Some light sources require a minimum level to turn on. Once these lamps are on, they can be dimmed down to lower light levels. At the same time, most common dimmers are built to dim at a uniform rate, regardless of the individual characteristics of each lamp or the number of lamps.

The properties and dimming characteristics of each new lamp and ballast on the market present a new challenge to the dimmer manufacturer to provide an appropriate dimmer. What was designed as a standard incandescent dimmer must now be able to control electronic ballasts, incandescent lamps, transformered low- voltage track lighting, and a host of electronic transformers.

One way to solve many of these problems is to tailor the style of dimming for each individual dimmer in a system. The way to do this is to apply different dimming curves to each dimmer and to provide a variable low- end cut-off point.

A dimming curve is a graphical or electronic representation of the amount of control to a dimmer in relation to the dimmer output. It is like a directional map followed by the dimmer. The amount of control is typically measured in percentages, from an off-state at level 0 to an on-state at level 100. Dimmer output is measured in volts. A graphical representation of a dimming curve is usually the percentage of dimming in relation to the output voltage (RMS) of the dimmer connected to a standard load.

AMX Lighting curve changes are implemented by a command to the AMX Lighting device. This example would set dimmer channel #1 to curve 6. The available curves that can be sent to the AMX Lighting controller are: 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, N, O, R, and F.

The Radia Eclipse controllers can employ a low-end cut-off that allows the dimmer to turn on to a specified level or to dim down to no less than a specified level. This level at which the dimmer turns on is called the Low End Setting. This is also used to turn a light off at the low end point when dimming down from a bright level. A low end setting of 25 applied to the standard dimming curve would prevent the fixture from being dimmed below Level 25. From an off condition, the same fixture would dim up to Level 25 and hold that level until the dimming curve directed the level higher.

If a fixture flickers just before it goes out, then the Low-End Setting can be used to avoid the unusable dimming range. Setting the Low-End Setting to just above the level where flickering problem starts will prevent the dimmer from allowing the flicker to be seen.

RE-DM4 and RE-DM6 RADIA Eclipse Dimmer Modules 49