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Appendix B: AMX Lighting Curves
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AMX Lighting PROlink/AXlink Programming
Appendix B: AMX Lighting Curves
There are thousands of different lighting fixtures with unique shapes and styles 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.
There might be 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 a long time 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 ability 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, there are many lamps that do not start to
display dimming until less 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 with no respect for the individual characteristics of each lamp or the number of lamps.
There is a great influx of new lamps and ballasts on the market. The properties and dimming
characteristics of each one 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 that the dimmer follows. The amount of
control is typically measured in percent; from an