History of Dimmers
– Early dimmers were controlled through large dimmer panels.
– In 1896, Granville Woods patented the Safety Dimmer, reducing wasted energy.
– In 1959, Joel S. Spira invented a dimmer based on a solid-state switching device.
– In 1966, Eugene Alessio patented a light bulb socket adapter for adjusting light levels.
– Analog remote control systems became feasible with solid-state dimmers.
Types of Dimmers
– Rheostat Dimmer:
– Rheostat dimmers were inefficient and required cooling.
– The dimming effect depended on the load applied to each rheostat.
– Mechanical control made it difficult to change many channels at once.
– Salt Water Dimmer:
– Salt water dimmers used a movable and fixed contact in a liquid medium.
– Voltage availability for the light depended on the contact distance.
– Regular maintenance and corrosion were issues with salt water dimmers.
– Coil-Rotation Transformer:
– Coil-rotation transformers used fixed and variable coils to vary voltage.
– The secondary coil canceled out opposing fields from the primary.
– Rotor and stator components resembled those in an electric motor.
– Autotransformer Dimmer:
– Autotransformers closely resembled rheostat dimmers but were more efficient.
– Voltage output and dimming effect were independent of the load applied.
– Remote control of autotransformers was impractical but some had motor drives.
– Solid-State Dimmer:
– Solid-state dimmers were introduced to solve inefficiencies of previous types.
– Thyristor dimmers and SCR-based light dimmers are examples of solid-state dimmers.
– Solid-state dimmers offer improved efficiency and control over light output.
Control and Patching
– Control:
– Dimmers can be controlled remotely using various protocols.
– Analogue dimmers require a separate wire for each channel of dimming.
– Serial analogue protocols were developed in the late 70s.
– Digital protocols, such as DMX512, have been widely used since the late 80s.
– Modern dimmer designs use microprocessors for closer control and diagnostic feedback.
– Patching:
– Patching is the assignment of circuits or channels for control.
– Hard patching involves permanent wiring between dimmers and lights.
– Theatres often use patch bays to provide flexibility for changes during shows.
– Soft patching is commonly used in modern fixed installations with dimmer-per-circuit setups.
– Dimmers can be patched into channels using computerized control consoles.
Dimming Curves and Preheat
– Dimming curves:
– Most analogue dimmers have non-linear output curves.
– Different applications demand different dimmer responses.
– Television often uses a square law curve for finer control.
– Theatrical dimmers tend to use a softer S or linear curve.
– Digital dimmers can have user-programmable or non-standard curves.
– Preheat:
– Switching high-intensity incandescent lamps to full power from cold can shorten their life.
– This is due to the large inrush current that occurs.
– Preheating the lamps reduces stress and extends their lifespan.
– Preheat dimmers gradually increase the power to the lamps.
– This allows the filaments to warm up before reaching full power.
Types of Dimmers (Continued) and Additional Topics
– Types of Dimmers:
– Semiconductor dimmers switch on at an adjustable time after the start of each alternating-current half-cycle.
– Dimmers based on silicon-controlled rectifiers (SCRs) use phase-angle control.
– Dimmers based on insulated-gate bipolar transistors (IGBTs) chop off the falling side of the sine wave.
– Sine-wave dimming is a newer technology implemented as a high-power switched-mode power supply followed by a filter.
– Leading-edge dimmers work well with incandescent lamps, while trailing-edge dimmers work well with LED lamps.
– Digital:
– Modern digital desks can emulate preheat and dimmer curves.
– Soft patching can be done in memory.
– Different profiles can be programmed and used on different channels.
– Dimmer racks can be easily exchanged without transferring complicated settings.
– Digital desks offer flexibility and convenience in lighting control.
– Rise time:
– Rise time is a measure of the quality of a leading edge dimmer.
– It is the time taken for the cut part of the waveform to reach the instantaneous output voltage.
– Longer rise time reduces noise and extends lamp life.
– Longer rise time also reduces electromagnetic interference.
– Implementing longer rise time is more expensive due to increased choke size.
– See also: Avolites, Choke, Compulite, Derating, Fluorescent lamp
– References: Patent US569443 – Granville t., Lutron Electronics Donates Company History to National Museum of American History, Patent US3032688 – Dimming device, Patent US3452215 – Light bulb socket adapter, Open Lighting Architecture
– External links: Wikimedia Commons has media related to Lighting dimmers, Lutron Electronics, Inc., Asia.lutron.com, Can You Put LED Lights On a Dimmer? – Energy Today, Strand Dimming Systems (PDF) Source: https://en.wikipedia.org/wiki/Dimmer
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A dimmer is a device connected to a light fixture and used to lower the brightness of the light. By changing the voltage waveform applied to the lamp, it is possible to lower the intensity of the light output. Although variable-voltage devices are used for various purposes, the term dimmer is generally reserved for those intended to control light output from resistive incandescent, halogen, and (more recently) compact fluorescent lamps (CFLs) and light-emitting diodes (LEDs). More specialized equipment is needed to dim fluorescent, mercury-vapor, solid-state, and other arc lighting.
Dimmers range in size from small units the size of domestic light switches to high-power units used in large theatrical or architectural lighting installations. Small domestic dimmers are generally directly controlled, although remote control systems (such as X10) are available. Modern professional dimmers are generally controlled by a digital control system like DMX or DALI. In newer systems, these protocols are often used in conjunction with Ethernet.
In the professional lighting industry, changes in intensity are called "fades" and can be "fade up" or "fade down". Dimmers with direct manual control had a limit on the speed they could be varied at but this problem has been largely eliminated with modern digital units (although very fast changes in brightness may still be avoided for other reasons like lamp life).
Modern dimmers are built from semiconductors instead of variable resistors, because they have higher efficiency. A variable resistor would dissipate power as heat and acts as a voltage divider. Since semiconductor or solid-state dimmers switch quickly between a low resistance "on" state and a high resistance "off" state, they dissipate very little power compared with the controlled load.
Most recently, software programmable internal dimmers can use signals from the same switch that turns lights on and off to control dimming. No dedicated external dimmer is needed. A simple communications protocol, such as Blink'n'Dim, delivers dimming commands via the power line. They enable computer control via networked switches, but do not require it. Their cost is about the same as the older "dimmability" circuitry that they replace in LED bulbs, fixtures or drivers.
