Dimmers Overview
       
Dimmer Circuit Block Diagram

Dimmers control the stage lighting by regulating the flow of electricity through the lamps. The diagram (left) shows the main parts of a dimmer circuit.

Each dimmer receives electricity from the AC mains supply and a control input from a lighting desk. The dimmer output is the amount of electricity between 0% and 100% of the AC mains that corresponds to the level set for it on the lighting desk.

Most dimmers use a triac or a pair of SCRs (thyristors) that are switched on and off very rapidly by their control circuit to dim the lamps using a technique called phase control. The choke helps filter out unwanted radio interference that is generated by the triac switching.

Dimmers are made to work with different types of analog or digital control signals from lighting desks. Analog systems commonly use a 0 - 10V DC signal and require a separate wire from the lighting desk for each dimmer channel, while digital systems using the DMX-512 protocol require just one pair of wires to carry all the data from the lighting desk for 512 dimmer channels.
Revised: 21-Dec-2008 Copyright (C) 2005 Adena Limited