Dimmer

A dimmer is a device which takes a normal mains voltage (i.e., 240V 60Hz AC) and changes it to a variable voltage. This allows you to change the brightness of a lamp.

Control
Almost all modern permanent dimmers are controlled by the DMX protocol. This allows each dimmer to be assigned a DMX channel between 1 and 512 and a value between 0 and 255. However older dimmers, especially portable dimmers, use an analog signal to set values.

Capacity
Each dimmer has a maximum capacity. This is the maximum amount of power the dimmer can output at the same time. Permanent dimmers usually give this value in Kilowatts (kW), but portable dimmers may give the value in Amps (A). You can convert between the two with the following equation:. Remember that the voltage is 240 volts. If you exceed the maximum capacity of the dimmer, it may trigger the fuse, in which case you may lose some dimmers until you reset them, or it may potentially cause a fire if too much current is going through a single cable. You can reduce the load on the dimmer by spreading fixtures over multiple dimmers, or using a dimmer with a higher capacity.

Power Supply
Whilst you do not need to know much about the power supply for permanent dimmers, you will need to take it into consideration when using portable equipment. See Outdoor Lighting.

Non-dim Circuit
A non-dim circuit is effectively a switch. They may just be controlled by a manual switch or by DMX. The main purpose of an NDC is to power a device which is designed to be connected directly into unfiltered mains electricity. By having it built in to the building, it allows easy integration with sockets on the lighting grid. Devices that need an NDC are anything which is more than just a simple lamp (such as Intelligent Fixtures and Hazers). This is because of the way most dimmers work. Instead of varying the voltage, most just to turn the output on and off at a high frequency to reduce the average voltage (see [[Media:Dimmer-waveform.gif|image]]). For electrical circuits, this can cause problems, even when the dimmer is at 100%.