Lighting Used To Be Simple

In 1878 there were just gas lamps and carbonised bamboo filament lights. But that was then and now is now. Things have got quite complicated. Lamps are classified by power requirements (single phase vs three-phase), light-generation principle, technology, cap/base type, wattage and shape. The discussion below omits wattage and shape because time is short (this is also the reason for the lack of pictures).

For each light-generation principle used, a number of variants exist (refered below as engineering technology) which aim to improve efficiency, lifespan, light colour or just make the lamp more compact. These are marketed under a varierty of names and we highlight the main ones (in the EU and US markets) under "Aka". Sometimes the "common" name for a lamp is actually its cap/base designation as it is common to design new caps for new lamp types (to avoid putting the wrong lamp in the wrong fit/socket).

Typical figures for efficiency (lumens per watt) and lifespan (operating hours) are given but please note that lamps labelled "long life" tend to use better components and tigher engineering that can double typical lifespans. Always consult the manufacturers specs.

As a general rule any incandescent, fluorescent and neon light can be dimmed. High Intensity Discharge (HID), Induction and Ligh Emiting Diode (LED) lamps (as of 2003) cannot be dimmed although some manufacturers are developing dimming kits for certain HID lamps. But as of today the best way to go about dimming the undimmable is to install two fittings side-by-side and switch them. A dual installation with, say a 70W and 150W, can then give you 3 "dimming" points (70W, 150W and 220W).

Single Phase lamps (ie. your bog-standard 110V/220V/240V)

Three-phase Lamps

TO BE PREPARED

Explanation of Terms

Candela (cd). Unit of luminous intensity.

Category 1,2 and 3. A (UK) health and safety designation that refers to the angle of incidence of light. The intention is to protect people's eyes from strong light reflections from VDUs by setting a maximum angle from the vertical from which you can see direct light. For Category 1 (high density screens), the maximum angle is 55^o (ie. you can see the direct light at angles 55^o and below). Category 2 (typical office) is 65^o and Category 3 (casual use of computer terminals), 75^o. Obviously, an angle of 90^o implies that one can see the light source directly (ie. no protection) from any angle. Compliance with these requirements can be achieved by installing a specially designed louvres or simply, pointing the light upwards.

Colour. In lamps, the equivalent temperature of the generated light. Typically between 2700K (orange-ish colour) to 4100K (blue-ish colour). 3500K is regarded as neutral. In office spaces, it is common to use cooler lamps (4000K). Lamps are available from 2000K to 6500K. See also CRI.

CRI. Colour Rendering Index. While the "colour" of the light is measured in K, the ability to light objects naturally is measured by the Colour Rendition Index (in a scale 0-100, where 100 is equivalent to natural sunlight). It represents the ability of a lamp to render illuminated object's colour accurately. High colour rendition allows us to see objects, as we would expect them to appear under natural sunlight.

DALI. Digital Addressable Lights Interface. A common two-way 19-bit digital control interface for fluorescent lighting derived from DSI (see below), released around 1996 and finally adopted as international standard in 2002 (first shipments of commercial products started in 1998). DALI systems are currently available for T5, T5HO, T8, and compact fluorescent lamps (and promised for HID lamps) using NEC Class 1 (High Voltage, AWG18+, 1mm diam or greater) or NEC Class 2 (low voltage, AWG20/22, 0.8mm diam or smaller) wire. Converters exist to convert DALI commands to DSI (for retrofitting) and gateways to DMX512, RS232 and TCP/IP protocols. A single loop can control up to 64 lamps. The signal is 0/16V (polarity free) traveling at 1200bps. Max run is 300m (1.5mm2 cable). Latest ballasts have even a "lamp failure" alert - which can be handy if you have over half-million square feet of illuminated space (ie. about 10-20 lamp failures a day!). See also DSI below and Dali Organisation.

DALI Intensity Broadcast. Indicates that there is only a subset of DALI commands available. Specificially, no ability to address individiual ballasts.

Dichroic reflector. Reflector which lets the heat out thus gives a "cooler" light (normal aluminium reflectors let heat out mostly through the glass/front). Watch out, dichroic reflectors can only be used if the fitting and location allow for such mode of heat dissipation. To prevent installing a dichroic reflector in unsuitable fitting a special cap (GZ10) was designed. You can install a GU10 (non-dichroic) and GZ10 (dichroic) lamp in a GZ10 socket, but you cannot fit a GZ10 (dichroic) lamp in a GU10 (non-dichroic) socket (but watch out - not all luminarie manufacturers follow this convention).

Diode lamps. These are actually (old) halogen lamps (e.g. PAR20) which contained a small diode to rectify the current. They can be dimmed but better avoided altogether. They have been discontinued.

DMX512. Probably the first digital light control system. Originally developed in 1987 to support lighting of public venues such as theatres, concerts, etc.

DSI. Digital Serial Interface. A two-way (fault/error report only) 8-bit open standard (license free) to control dimming of non-incandescent lighting. Initially developed by Tridonic in 1991. Signal is 0/12V (polarity free) travelling at 1200bps. Max run 250m. Interfaces to RS232, C-Bus2 and DALI. Cheaper than DALI (see above) for medium-size installations (no logical addressing).

Fluorescent lamps. Operate by creating a UV arc which excites a coating of phosphor. The fluorescent is filled with an inert gas (nowadays Krypton). The process is controlled by specially designed circuit (called "ballast" or "control gear"). Compact fluorescent's have miniaturised control gear built-in. High frequency (30-40kHz) fluorescents convert mains frequency signal into a higher frequency resulting in better efficiencies (about 20%) and lower noise.

Halogen lamps are tungsten lamps where some traces of a halogen (bromine, chlorine, iodine) have been added plus quartz (rather than glass) lamp capsule, which gives a 2-3 longer life span than standard tungsten.

High Intensity Discharge (HID). A lamp that produces light by passing electricity through gas, which causes the gas to glow. Examples of HID lamps are mercury vapour lamps, metal halide lamps, and high-pressure sodium lamps. HID lamps have extremely long life and emit far more lumens per fixture than do fluorescent lights.

Incandescent lamps. Light is generated by heating a high resistance filament (tungsten) in a inert gas, they are the most inefficient and with the shortest life span.

Induction lamp. An electrode-less lamp. A high frequency current creates an electromagnetic field which excites mercury atoms in the lamp's gas, these emit UV radiation which excites a coating of phosphor (similar to fluorescent lamps).

LED lamp. Ligh is generated by a low voltage light emitting diode.

Lumen (lm). Total amount of light emitted (= to candelas x surface). A light producing one candela gives 4*pi (approx. 12.6) lumens (assuming light is uniform in all directions).

Neon lamps. Uses a high voltage (3KV to 6KV) source (provided by a transformer) to excite an inert gas (neon).

PAR lamp. PAR is an acronym for "parabolic aluminised reflector" and is used to designate a sealed-beam lamp similar to the headlight in an automobile. PAR lamps are differentiated according to their diameter, which is measured in eighths of an inch. Therefore, a PAR64 is eight inches in diameter (64/8 = 8) and a PAR38 has a diameter of four and three-quarter inches (38/8 = 4.75). PAR lamps are available in an assortment of wattages and beam spreads as well. For example, a PAR56 lamp may be purchase at 300 or 500 watts, and each wattage is available in Narrow Spot, Medium Flood or Wide Flood.

PWM. Pulse Width Modulation. A dimming technique via which the dimming factor is transalted into a DC voltage pulse of variable duration.

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