Abstract

A dimming control system includes dimmer modules which receive dimming level information from a control module. Each dimmer modules includes a microprocessor which provides internal intelligence for controlling power to a load in response to the dimming level information. The control module receives industry standard protocol dimming information from various sources, converts it to dimming level information, and communicates the dimming level information to the dimmer modules through serial communication lines. The dimmer modules and control module are mounted in a rack which includes a backplane having nonvolatile memory device that retains configuration data even if the control module is removed from the rack. The dimmer modules implement a zero cross prediction method which includes detecting an actual zero cross, calculating an error, and adding the error to the period of a line power signal. The error is calculated by applying a median filter to a plurality of previous error values, discarding the highest and lowest values of the previous error values, and averaging the remaining previous error values.