Multifaceted reflector: Difference between revisions
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== Variations == |
== Variations == |
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MR16 lamps most often operate at 12 volts, although they are also available in other voltages. |
MR16 lamps most often operate at 12 volts, although they are also available in other voltages. The common 12-volt MR16 lamps, therefore, require a [[ferromagnetic]] or electronic [[transformer]]—sometimes misnamed as a ''[[electrical ballast|ballast]]''—to convert the 120- or 230-volt [[mains electricity|mains voltage]] to the [[extra-low voltage|very low]] operating [[voltage source|voltage]] required by the lamp. MR16 lamps may also be operated from direct current, but will have a shortened life. |
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Some LED devices will not include current control and thus require the transformer to be a current source and provide the exact current to match the lamp (rather than exact voltage...) |
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Although halogen incandescent MR16 lamps usually operate on AC voltage, LED devices require direct current and require a [[rectifier]] and [[current source|current]] driver in the unit. The current driver is commonly a [[buck–boost converter]] or [[buck converter]]. The rectifier must be able to operate efficiently at the high [[frequencies]] produced by electronic transformers and should also incorporate safety devices that operate in the event of component failure.<ref name="safe_rectifier">[http://www.maxim-ic.com/app-notes/index.mvp/id/4708]{{Dead link|date=March 2012}}, MAXIM: LED driver solution for MR16 and similar retrofit lamps</ref> |
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Flourescent and LED devices may have two further compatibility problems. Lamps that are 12 volt input may not handle the high frequency ripple produced by transformers designed for incandescent lamps. The 12 volt transformer designed for incandescent lamps may not operate correctly at the low power (low current) used by the low power lamp. What is happenning is that when the transformer is used at low power (low current), the switching frequency is out of spec and the transformer produces a high frequency ripple on the voltage. Often the lamp manufacturer blames the transformer, while the transformer manufacturer will say the lamp should cope with its output. |
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<ref name="safe_rectifier">[http://www.maxim-ic.com/app-notes/index.mvp/id/4708]{{Dead link|date=March 2012}}, MAXIM: LED driver solution for MR16 and similar retrofit lamps</ref> |
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Certain MR16 lamps can operate directly on the mains voltage. These lamps typically use a GU10 turn-and-lock base, each pin looking like a metal mushroom, so they cannot be accidentally interchanged with low-voltage lamps. The GU10 base looks like a larger version of the base of fluorescent tube's starters. When the lamp has the GU10 base, they are often referred to as GU10, rather than MR16. Mains voltage MR16 lamps were not popular for incandescent technology, because their filaments are finer, and so they are much more fragile than the low-voltage lamps. This means that they would fail more often. {{Citation needed|date=February 2012}}. The GU10 down lamp using fluorescent or LED technology is the way to go for future installations, as the use of mains power bypasses the issue of the transformer compatibility. There are cheap GU10 sockets available that will retro-fit into MR16 bases with ease. The GU10 format LED (or Fluorescent ) lamp will be far more popular than G24 standard downlamps, which were the only fluorescent equivalent of MR16 downlamps for a while. |
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Low-voltage MR16 lamps almost always have ANSI standard GU5.3 two-pin bases, and yet are still labelled in shops as MR16. The GU5.3 pins are straight , push in, pins . |
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MR16 lamps with an integrated transformer are also available. These lamps may have screw bases to fit standard medium-base [[Edison screw|Edison sockets]]. |
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Certain MR16 lamps can operate directly on the mains voltage. These lamps typically use a GU10 turn-and-lock base, so they cannot be accidentally interchanged with low-voltage lamps. They are often referred to as GU10, rather than MR16 lamps. Low-voltage MR16 lamps almost always have ANSI standard GU5.3 two-pin bases. MR16 lamps with an integrated transformer are also available. These lamps have screw bases to fit standard medium-base [[Edison screw|Edison sockets]]. |
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Smaller lamps are also manufactured in the less common MR11 and even less common MR8 formats, which have reflectors that are 1⅜ inch (11/8" or 35 mm) and 1 inch (8/8" or 25 mm) in diameter, respectively. These smaller lamps appear very similar to MR16 lamps, also featuring similar multifaceted reflectors that are available in a variety of beam spreads. Their smaller size makes possible even smaller fixtures, but limits them to lower powers. MR11 and MR8 lamps have pins placed closer together, preventing them from accidentally being interchanged with MR16 lamps. |
Smaller lamps are also manufactured in the less common MR11 and even less common MR8 formats, which have reflectors that are 1⅜ inch (11/8" or 35 mm) and 1 inch (8/8" or 25 mm) in diameter, respectively. These smaller lamps appear very similar to MR16 lamps, also featuring similar multifaceted reflectors that are available in a variety of beam spreads. Their smaller size makes possible even smaller fixtures, but limits them to lower powers. MR11 and MR8 lamps have pins placed closer together, preventing them from accidentally being interchanged with MR16 lamps. |
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Revision as of 01:48, 4 December 2012
A multifaceted reflector light bulb is a format for halogen bulbs, made by a variety of manufacturers. MR lamps were originally designed for use in slide projectors, but are now used in applications including residential lighting and retail lighting. They are suited to a variety of applications that require directional lighting, such as track lighting, recessed ceiling lights, desk lamps, pendant fixtures, landscape lighting, retail display lighting and bicycle headlights. Lamps are designated by symbols such as "MR 16" where the diameter is represented by numerals. Common sizes for general lighting are MR 16 and MR 11, with MR 8 used in specialty applications.
Compact fluorescent lamps and LED lamps interchangeable with some sizes of MR halogen lamps are now available.
Designation
MR16 is a coded designation in which MR stands for multifaceted reflector, and 16 is the diameter in eighths of an inch across the front face. An MR16 is sixteen eighths, or 2 inches (51 mm) in diameter and an MR11 is 11 eighths, or 1.375 inches (34.9 mm) in diameter.
A common derivative is known as GU10, a format invented by Havells Sylvania in 1997,[1] and is distinguishable from other MR lamps by the ceramic base and being mains voltage.
History
The MR16 lamp was first sold in 1965. Emmett H. Wiley of General Electric (USA) was awarded patent #3,314,331 for a miniature reflector lamp in 1967. The innovation was using the lamp rim, rather than the base, as the reference plane for focusing. This allowed more flexible electrical mounting arrangements and more precise focussing.[2] Note that this lamp was not "multifaceted"; faceted reflectors were introduced in 1971.
Halogen MR16 characteristics
Design and construction
Halogen MR16 lamps consist of a halogen capsule (bulb) integrated with a pressed glass reflector. The reflector of an MR16 lamp is 2 inches (51 mm) in diameter. The base conforms to bi-pin GU5.3 standard. The compact size of the MR16 allows for much smaller, more discreet fixtures than the incandescent reflector bulbs that pre-dated MR16s.
The reflector controls the direction and spread of light cast from the lamp. MR16 lamps are available with different beam angles from narrow spot lights of as small as 7° to wide flood lamps of 60°.
"MR" refers to the multifaceted reflector which has multiple small facets. This reflector gives a soft edge to the area illuminated by the lamp. MR16 lamps are also available with smooth reflectors, resulting in a sharper fall-off to the illuminated area.
Dichroic reflectors
Some lamps use an aluminum coating as a reflector. Others use selective dichroic coating that reflects visible light and allows infrared radiation to pass through. This type reduces heating of illuminated objects since less infrared radiation is present in the light beam. However, dichroic lamps must only be used in compatible fixtures that can dissipate the heat.[3] Dichroic lamps must not be fitted to recessed or enclosed luminaires with the IEC 60598 No Cool Beam symbol.[4]
Operation
The brightness of MR16 lamps can be adjusted when used with appropriate light fixtures and dimmers. However, the color temperature changes significantly when the lamp is dimmed.
MR16 lamps produce significant heat, and care must be taken to avoid contact with skin or proximity to flammable materials when the lamp is on or has been on recently.
Low voltage halogen lamps, such as MR16 lamps often have a better efficacy than line voltage incandescent lamps but not nearly as efficient as gas discharge lamps or some LED lamps.[quantify]
With both types of incandescent bulbs, useful life can be considerably shortened if their filaments experience mechanical shock or vibration. Using an electronic transformer with a "soft start" feature can considerably extend life, as it reduces the characteristically high inrush current that occurs initially when the lamp is cold. Dimming also extends life significantly.
MR16 lamps, like all quartz-halogen lamps, produce some ultraviolet light. Usually, this must be filtered out. Also, the quartz capsule of the lamp sometimes ruptures ("explodes") upon failure of the lamp. For these two reasons, some MR16 lamps include a cover glass that serves as an integrated ultraviolet filter and explosion shield. MR16 lamps lacking this cover require the use of a fixture that incorporates an external piece of glass specifically designed to provide this protection.
MR16 lamps are available in 10–50 W power ratings (150–800 lumens).[5]
Alternatives
MR16-compatible LED lamps are also available. They are similar in shape to halogen MR16 lamps, and can be used in most fixtures designed for MR16 lamps. The same is true of MR11-compatible LED lamps. Fixtures designed for halogen MR16 or MR11 lamps that use electronic transformers may need to be retrofitted with LED-compatible transformers. There is a wide variety of designs, varying significantly with regard to beam width, light colour, efficiency and luminous power.
Unlike halogen MR16s, LED-lamps often do not have the multifaceted reflectors that give MR16s their precise beam width control. Some rely on the optics of the LED(s) to control the beam width. Some designs may have simple cut-off apertures that limit beam width, or even individual reflectors for each LED.
As with other LED lamps available today, the quality and color temperature of the white light produced by such lamps varies. Many tend towards the blue end of the spectrum, being even "cooler"-coloured than fluorescent lighting. Because of this variability, some MR16 and MR11 compatible LED lamps will create significantly more natural looking light than others.[citation needed]
The least efficient of these lamps produce about 26 lumens per watt (lm/W), which is similar to the efficacy of halogen MR16s. The most efficient of these lamps available today produce about 100 lm/W, which exceeds the efficacy of compact fluorescent lamps.
In terms of total luminous power, such lamps range from being significantly less powerful than their halogen counterparts, to being comparable to the lower power halogen MR16s. The brightest available halogen MR16s are still slightly brighter than the brightest available LED versions.
MR16-compatible compact fluorescent lamps are also available. As of 2012 they tend to be cheaper than LED replacements and have comparable efficiency, but they may not be available with high output or with narrow flood angles.
Variations
MR16 lamps most often operate at 12 volts, although they are also available in other voltages. The common 12-volt MR16 lamps, therefore, require a ferromagnetic or electronic transformer—sometimes misnamed as a ballast—to convert the 120- or 230-volt mains voltage to the very low operating voltage required by the lamp. MR16 lamps may also be operated from direct current, but will have a shortened life.
Although halogen incandescent MR16 lamps usually operate on AC voltage, LED devices require direct current and require a rectifier and current driver in the unit. The current driver is commonly a buck–boost converter or buck converter. The rectifier must be able to operate efficiently at the high frequencies produced by electronic transformers and should also incorporate safety devices that operate in the event of component failure.[6]
Certain MR16 lamps can operate directly on the mains voltage. These lamps typically use a GU10 turn-and-lock base, so they cannot be accidentally interchanged with low-voltage lamps. They are often referred to as GU10, rather than MR16 lamps. Low-voltage MR16 lamps almost always have ANSI standard GU5.3 two-pin bases. MR16 lamps with an integrated transformer are also available. These lamps have screw bases to fit standard medium-base Edison sockets.
Smaller lamps are also manufactured in the less common MR11 and even less common MR8 formats, which have reflectors that are 1⅜ inch (11/8" or 35 mm) and 1 inch (8/8" or 25 mm) in diameter, respectively. These smaller lamps appear very similar to MR16 lamps, also featuring similar multifaceted reflectors that are available in a variety of beam spreads. Their smaller size makes possible even smaller fixtures, but limits them to lower powers. MR11 and MR8 lamps have pins placed closer together, preventing them from accidentally being interchanged with MR16 lamps.
MR16 lamps are commonly available in range of color temperatures, from about 2700 K to 7000 K, to satisfy various applications.
Advantages
MR16 lamps offer several advantages over other lamps with equivalent power ratings. They are typically smaller (transformers excepted), provide better beam control and offer a whiter light than ordinary incandescent lamps. The small size of the lamp allows designers more flexibility in placing the lamps and with the option of various beam widths, the light beam can be very specifically placed.
White LED MR16 lamps can be manufactured with different colour temperatures, normally ranging from warm whites, attempting to match the colour of halogens, all the way through to cool whites at 5500 K or more.
Disadvantages
MR16 lamps have several disadvantages over other types of lighting, most notably their high operating temperature and pressurized bulb. The halogen bulb can reach temperatures over 200°C,[citation needed] increasing the risk of fire should anything flammable come in contact or even be in close proximity to the bulb or fixture. The quartz capsule containing the filament and halogen gas is pressurized and can explode if improperly handled or damaged, and must be handled carefully prior to installation to prevent contamination with oil and salt from fingerprints, which can dramatically shorten the lamp's life.[citation needed]
Mounted clear of roof insulation and with an inbuilt air space around the luminaire fitting, they effectively form small chimneys resulting in heat lost from the room space to the roof space.[7]
In dusty environments, the high temperatures produced contribute to a burnt smell.[citation needed]
ANSI designations
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The following ANSI standard codes are used to designate certain power and beam angle combinations for MR16 lamps. Many manufacturers use these standard codes for lamps matching these specifications:
- ESX: 20 watt, 10 degree beam (20MR16/10°)
- BAB: 20 watt, 35 degree beam (20MR16/35°)
- EXT: 50 watt, 15 degree beam (50MR16/15°)
- EXZ: 50 watt, 25 degree beam (50MR16/25°)
- EXN: 50 watt, 40 degree beam (50MR16/40°)
- FNV: 50 watt, 60 degree beam (50MR16/60°)
- FPA: 65 watt, 15 degree beam (65MR16/15°)
- FPC: 65 watt, 25 degree beam (65MR16/25°)
- FPB: 65 watt, 40 degree beam (65MR16/40°)
- EYF: 75 watt, 15 degree beam (75MR16/15°)
- EYJ: 75 watt, 25 degree beam (75MR16/25°)
- EYC: 75 watt, 40 degree beam (75MR16/40°)
Note that MR16 lamps are available in many other power and beam combinations than those available above. For this reason, MR16 lamps are also often labeled according to beam spread abbreviations. Note that these while these abbreviations are commonly used, the angles associated with these abbreviations vary slightly from manufacturer to manufacturer. Typical beam angles for these beam spread abbreviations are as follows:
- VNSP (very narrow spot): less than 8 degrees
- NSP (narrow spot): 8-15 degrees
- SP (spot): 8-20 degrees
- NFL (narrow flood): 24-30 degrees
- FL (flood): 35-40 degrees
- WFL (wide flood): 55-60 degrees
- VWFL (very wide flood): 60 degrees or more
See also
References
- ^ "Direct LED Replacement Launched". Sylvania press release. Retrieved 28 February 2012.
- ^ http://www.lamptech.co.uk/Spec%20Sheets/TH%20RM%20Q150MR16-21%20EJM%20GE.htm
- ^ Incidents – Cheshire Fire and Rescue Service
- ^ Downlighters and fire safety – Electrical Safety Council
- ^ "Replace Inefficient MR16 Halogen Lamps with LEDs". Maxim. September 25, 2007.
- ^ [1][dead link], MAXIM: LED driver solution for MR16 and similar retrofit lamps
- ^ [2], BB0502: Air Leakage in Recessed Lights