Stage Lighting Dimming
A dimmer is a device used to vary the electrical power delivered to the instrument’s lamp. As power to the lamp decreases, the light fades or dims. It is important to note that some color change also occurs as a lamp is dimmed, allowing for a limited amount of color control through the dimmer. Fades can be either UP or DOWN, that is increasing or decreasing the intensity. Today, most dimmers are solid state, although many mechanical dimmers still exist.
Dimmers are often found in large racks that draw large amounts of three-phase electrical power. The dimmers themselves are often removable modules that range from a 20-amp, 2.4 Kilowatt unit to a 50-amp or even a 100-amp unit. They can often be replaced by a Constant Power Module (CPM) which is basically a 20- or 50-amp breaker in a dimming module casing. Constant Power Modules are used to supply non-dimming current to other electrical devices (like smoke machines, chain winches, or scenic motors). When a Constant Power Module is installed, the corresponding circuit is energized as long as the dimming pack is on, independent of the lighting console. Failure to use a Constant Power Module on a non-dimming device can result in the damage of the device, specifically when the device relies on an internal transformer that depends on a specific power standard Even if a dimmer channel is trusted to always be operated at full power, during start up and shut down cycles of a lighting control surface, small amounts of noise interference and DMX signal-recycling can cause momentary interruptions in the data stream and cause a dimmer to dim a circuit, so a CPM is necessary to ensure that equipment is not damaged. (in the US, 110V-60Hz power).
Increasingly, with the growth of digital technology, modern lighting instruments are available which allow remote control, not just of intensity, but of direction, color, beam shape, projected image, beam angle and a wealth of other effects. The ability to move an instrument ever more quickly and quietly has become the industry goal. Such automated lights frequently have built-in dimming and so are connected directly to the control cable or network and are independent of external dimmers.