Community Theatres have three main types of lighting equipment to control.
Conventional Lighting – These use a Tungsten Halogen Lamp and generally use a Dimmer to control the brightnes or intensity of the lamp.
Initially they used a Tungsten Lamp, in this example it is a T1 P28S Prefocus 500W lamp. These lamps needed a preheat voltage, usually 5% of maximum operating voltage to warm up the filament, so that it did not fail prematurely, due to thermal shock. The Tungsten from the filament would eventually migrate to the inside of the glass envelope, darkening the glass and reducing the light output.
The next generation of Tungsten Halogen lamps were filled with an inert gas and a halogen gas that extended the life of the tungsten filament. The lamp housing was a quartz envelope that is damaged by skin oils so contact has to be avoided. They did not need a preheat voltage. Using a preheat voltage for long periods operated the lamp below its normal operating range and could shorten the lamp life.
This early Jands Roadpack dimmer has both Analog control. Later models also had DMX512 control. It is fitted with 3AG size 10Amp fuseholders. Each channel could control up to 2400Watts or 10 Amps. If a fuse ruptured due to overloading the channel or if a lamp filament failed and sorted, the fuse would have to be replaced with a new spare fuse.
This Jands HPC dimmer has resettable 10 Amp Magnetic Circuit Breakers or MCB’s on the front panel, to allow for restoring power after an overload or fault condition. This model has bypass relay switching for each channel to allow for use as an LED supply. Channels can be set to On, Remote Switch, Remote Dim or Off. Users must be careful not to connect LED lighting to a Dimmer configured output.
The LSC GEN VI has RCBO or combined MCB and Residual Current Breaker (or “Safety Switch” , a non technical term used by electrical safety authorities) for improved personal safety. RCBO can be identified by the Test button on the top of the breaker.
There is an excellent article explaining The Use Of Earth Leakage Circuit Breakers With Lighting Controls on the Theatrecrafts website https://www.theatrecrafts.com/archive/documents/factsheet02_elcb.pdf note the website is an excellent resource.
Discharge Lighting – These use a Discharge Lamp that is struck at power on and stays on. A shutter is used to dim or control the amount of light output.
There is a large power surge when the lamp is struck, which limits the number of fixtures that be powered from the same circuit. Martin built in a staggered or successive lamp on control circuit to avoid overloading or tripping circuit breakers.
LED Lighting – These have inbuilt electronic control circuitry to control the brightness or intensity of the light output. This is a Huayin Lighting HY-P186S RGBWAU/V LED PAR. There is a 200W electronic Switch Mode Power Supply or SMPS to supply power to the electronics, mounted inside the unit. The control boards are mounter on the rear cover, next to the PowerCon In and Out scokets. These Switch Mode Power Supplies should have a leakage of less than 5mA, typically 0.5mA
As an RCBO or RCD has a typical trip current of 15 to 20 mA, you need to limit the number of LED fixtures on each channel to less than the tripping current.
LED Power Distribution units such as the Theatrelight Contact 12 can switch each output power circuit sequentially at times intervals, to overcome tripping due to excessive power surges, or leakage current of SMPS.
“Easy to set up and use, the Contact 12 provides switched power via DMX control with user settable security delays, or auto sequential power on for Moving Lights, LED luminaires, fireworks, motors, and any other appliance requiring reliable On/Off power.”
“The Auto Sequential On mode is particularly useful where large installations of LEDs and Moving lights trip MCBs when all circuits are switched on together. 30 amp rated Omron relays provide longterm reliability.
Using units such as these will help prevent tripping of circuit breakers in the Control Room Switchboard,
updated 12 August 2025