Transcript Chapter 6 Intensity Control

Notes taken from
Michael Gillette’s
Designing With Light

Company Switch



A disconnect box to which
portable dimmers may be
connected
Normally 240 VAC
Located in wings

Every theatrical lighting system is made up of
three components
Dimmers
 Dimmer Control
 Electrical Distribution


Two kinds of Dimmers


Mechanical
Electronic

Involved direct physical movement of
mechanical components, not frequently used in
theatre anymore

Resistance Dimmer – Archaic dimmer using a
variable-capacity resistor
 Lights off - resistance increased energy converted to
heat and does not reach the lamp
 Lights on - resistance decreased and current reaches the
lamps
 Difficult to use, requires a lot of space,

Saltwater Dimmer
 Oldest type of dimmer
 Involved dipping metal plates
attached to one leg of a circuit into
salt water with another set of
plates already immersed in the
water.
 Current dependent on depth of
metal plates being dipped.

Use a low-voltage current to regulate the highvoltage current

Autotransformer Dimmer



Rarely controls stage lights, but sometimes house lights
Control switch in booth regulates a mechanical linkage
that controls the dimmer and enables it to raise and
lower the lights
Motor runs a single speed so fades cannot be controlled

Autotransformer Dimmer

Silicon Controlled Rectifier
Dimmer (SCR)

Operates on a gating
principle
 On for 1 second – full
intensity
 On for ½ second, Off for ½
second – 50% intensity
 On for ¼ second, Off for ¾
second – 25% intensity

Solid state power transistor
 No moving parts, reliable

Silicon Controlled Rectifier Dimmer (SCR)

Digital Control Systems for Electronic Dimmers

The new “Standard”

Digital Control Systems for Electronic Dimmers

Analog
 Requires a constant signal
 Every dimmer in the system must be connected to the
light board by its own control line
 Line –The wires in low-voltage control systems

Digital Control Systems for Electronic Dimmers

Digital
 Discrete (separate and complete )steps
 binary code, on, off, 0, 1
 Multiplexing – can send multiple messages at the same
time
Analog
Digital

Group Master

Individual dimmers
controlled by a
submaster, which is
controlled by a grand
master

Preset



Two-scene Preset,
Three-scene Preset
Controls for each
dimmer are
repeated for two or
three scenes
Dimmers can be set
up for each scene
and using a fader
can be shifted from
scene one to scene
two

Combination


Combines preset and
group master
Provides more
options and
flexibility

Computer Memory




Most flexibility
Hard Drive – Device for
storing and retrieving
data
Back-up disk
Volatility –
Nonpermanence

Computer Memory
Channel Control – An electronic patching system
in which one or more dimmers can be assigned to a
control channel which in turn controls the
intensity level of those dimmers
 Group – grouping of two or more
dimmers/channels under one controller


Computer Memory

Timing capabilities
 Fade-in – gradual increase in intensity
 Fade-out – gradual decrease in intensity
 Split time fade – Fade up and out are at different
rates
 Delay - Refers to the time interval that the second
part of a split time fade follows the first