Monday, January 04, 2010

Led Strip Lighting Around Flat Screen TVs

Led Strip LightingThe Philips Ambilight LCD HDTV range have lights around the edges and on the back which claimed to reduce eye strain and make the colours look better. There are numerous online discussions of using Led Strip Lighting for a similar effect, including suggestions by Ikea with their DIODER lights. Most of these do not automatically adjust the light level and colour as Phillips claim to do. But the effect might also be useful for desktop LCD computer screens, with the lighting strips providing subtle and efficient lighting for a desk. The lighting strips are now commonly available.

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Tuesday, June 02, 2009

LED Downlights

Lights of America 2001LED53IN-65K-24 LED 1 Watt MR16 GU5.3 Base Indoor Light BulbAt Kmart I noticed a Mirabella brand 12 Volt LED Dichroic MR16 light for about AU$15. These are similar to units sold by as LED 1 Watt MR16 GU5.3 Base. These are claimed to use 65% less energy than an incandescent globe. It has 15 small LEDs in place of one halogen bulb and uses only 1.1 Watt, instead of the usual 50 Watts. But there are a few catches: The MR16 lights are usually halogen lights, not incandescent globes. The halogen lights are more efficient than normal globes and so the LEDs are less of an improvement than otherwise. Also the LEDs give much less light than a 50 Watt globe (only 15 Lx at 3 metres). They also have a very focused beam (15%) compared to other units.

The LEDs are described as "White" (6500K), but have a blue tint compared to halogen lights. Another catch is that the LEDs do not work well with electronic transformers or dimmers. I found that on its own the LED light would not work at all, but might work if there were several halogen lights plugged in parallel with it. The LEDs cannot be dimmed, they flickered if the dimmer was turned way down.

These units would have some uses. If there is an area with a very large number of down lights, the LEDs can be used to provide sufficient light and an aesthetic look.

3 x 1 Watt CREE XR-E LED MR16 12V Warm White Light bulbThere are more practical units which use three 1 Watt LEDs but these cost around US$30 each (MR16 12V Warm White Light bulb). What might be more practical is to use lower power halogen lights (such as 20 Watt).

There are also 5 Watt halogen lights available, but these generally use a smaller fitting (MR11). Perhaps what is needed is a small metal disk to adapt the smaller MR11 to the larger MR16 fittings (an adaptor for the small electrical pins of the MR11 would also be needed). For less than $2 each, the power consumption of the lights could be cut by 90%. Of course it would be better to install the lower power MR11 in the first place, or even better another type of low power fitting. But there are many 50 Watt MR16 untis out there wasting power which could be converted.

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Sunday, May 10, 2009

Combine photoluminescent and LED pathmarking systems

Photoluminescent strips provide an alternative to electrically illuminated signs and pathway lights in some circumstances. While lumescent exit sigens are available, these do not meet Australian standards. One approach might be to combine the luminescent function with LEDs. The luminescent material used in these signs is also fluorescent. A UV LED will cause the luminescent material to glow brightly while the LED is on, as well as recharge the material so it will glow brightly when power is off. This might remove the need for complex battery backup power supplies for such signs. The LED would ensure that the luminescent material was fully charged. UV LEDs are relatively inexpensive and very efficient (most "white" LEDs are actually UV LEDs with a white phosphor coating to convert the UV to visible light).

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Monday, January 28, 2008

LINEARlight Flex LED Lighting

Roll of OSRAM LINEARlight Flex LED LightingOSRAM are offering flexible LEDs for commercial and home lighting, under the name "LINEARlight Flex". This consists of rolls of adhesive backed tape with LED lights every few cm. They have styles with the lights on the face of the tape or at the side and in colors as well as white. The have "CONNECTsystems" connectors and other accessories to power the lights and technical data available.

At present these systems seem to be design for accent lighting, not for general use. But as the cost of the LEDs goes down, and the price of electricity goes up, these could be sued for applications, such as offices and classrooms.

  1. LINEARlight Flex TopLED LM10A
  2. LINEARlight Flex SideLED LM11A
  3. CONNECTsystem for LINEARlight Flex LM2x-Flex
  4. Brochure: General lighting
  5. Brochure: Professional lighting
  6. OPTOTRONIC: Technical guide
  7. Application notes Corona-Effect


Tuesday, January 22, 2008

Waterproof LED lights

IP67 LED ModuleRecently I came across LED lighting modules which are claimed to be water proof (rated to IP67). They come in strings of ten lights, each with three LEDs, sealed in resin. Each light is connected to the next with a short cable and these can be cut so they can be used separately, with each one working out at $2. The lights are bright enough for illuminating a stairway.

Endless possibilities - backlighting signs, strip lighting in stairwells & passageways, boats, garages etc. Supplied with 3 LEDs per module, 10 modules, with 500mm flying leads for termination. Each module is spaced at approximately 110mm between centres. Simply connect up a 12VDC 600mA supply and away you go.

Two types:
ZD-0490 10 x 3 LED Module White
ZD-0492 10 x 3 LED Module Blue

• IP67 rated
• Waterproof and submersible
• Resin sealed
• Adhesive backed for quick installation
• Brightness per LED:
• White: 1200 - 1500mcd
• Blue: 600 - 800mcd
• Dimensions:
• Each module: 47(L) x 17(W) x 6(H)mm
• Total length: Approx. 1m
• LED spacing: 15.6mm

From: IP67 LED Modules, Jaycar Electronics, 2007

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Thursday, January 03, 2008

LEDs for office, home and classroom lighting

Flexible LED TapeLight emitting diodes (LEDs) are becoming affordable for general office, home and classroom lighting. They have about the same efficiency as compact fluorescent lamps and last much longer. There are now some LED replacement bulbs appearing to fit in ordinary light fittings. There are now also flexible strips of LEDs available which can be simply stuck to a surface. This allows more controlled lighting.

Griffith University's design guidelines recommend a maximum power density for lighting of 9 W/m² in general offices and classrooms, 5 W/m² in Corridors and 3 W/m² in stairway. It might be reasonable to aim to reduce this to 2 W/m² in offices and classrooms, by the use of more efficient directed light and task-lights, 1.5 W/m² in corridors and 1 W/m² in stairways.

LEDs have different characteristics to incandescent and fluorescent lamps. It may be more cost effective to build the LEDs into the fitting, instead of having a replaceable lamp. A LED will last about ten years when used for 12 hours a day. This makes it feasible to dispose of the whole fitting hen the lamp fails, particularly if the fitting consists of just a thin strip of plastic.

LEDs are small sources of light, usually about 2 mm square. So it has been difficult to make high intensity LEDs similar to halogen lamps or to cover a wide area like a fluorescent tube. There are now 1 Watt and 5 Watt LEDs available, but these require elelctronic circuitry to drive them and heat sinks to cool them. Instead what has become common is to group together a large number of low power LEDs (usually .1 Watt LEDs, each 5 mm in diameter of about 3 Lumen). When collected in a circle these LEDs are used to replace a spotlight, along a bar they replace a fluorescent tube and in a hemisphere they replace an incandescent bulb. The LEDs may be mounted on an ordinary light plug, allowing replacement in standard fittings.

While this overcomes some of the limitations of LEDs, this emulation of a conventional light does not exploit their features. It should also be noted that current LEDs at5 about 50 lm/W are only half as efficient as fluorescent tube lamps (70 lm/W). When a LED is placed in a conventional housing designed for an incandescent or fluorescent light, there is a further loss of efficiency.

However, LEDs operate at a safe low voltage, with each emitting a small amount of concentrated light and minimal heat. LEDs can be automatically connected in large numbers and on flexible substrates using equipment designed for assembling elelctronic circuits. This allows lighting fixtures with inbuilt lights which will provide light over a large but precisely controlled area.

Undercar Light KitSo an alternative for lighting might be to automatically assemble LEDs on sheets and strips, which could then be attached to a building. As an example strips can be stuck across a ceiling. There is no need for light fittings or wiring, the strip providing both the mounting and interconnect cable. These lights are provided in rolls and in strips with adhesive backing. The LEDs are being mass produced for backlights in LCD displays, and also as decorative undercar "neon" light strips for cars.

LED lights are not used for general office or classroom lighting due to the high levels specified in standards. This would result in a very large number of LEDs being needed. However, if the general lighting level was reduced and task lights used on desks, fewer lights could be used. As an example the Australian Standard AS 1680.2.2 - 1994 Interior lighting Part 2.2: Office and screen-based tasks specifies 300 to 400 lux Lux for task lighting and 160 lux for background illumination. However, the Australian Standard Building Construction Sites is 40 Lux for walkways and access areas and the future European standard for emergency lighting will be only 1 Lux.

A standard office has a ceiling made up of a 1200x600 mm grid. It would be convenient to attach the LED light strips to the grid (existing in-ceiling lights could be switched off but let in place). If attached along the 1200 mm sides of the grid, the lights would cover .6 of a square metre per meter. For walkway lighting at 40 Lux, the .1 Watt LEDs would need to be spaced 125 mm apart (8 lights per metre). If placed along the 600 mm sides, twice as many LEDs would be needed, about 60 mm apart. One or two strips could be used to illuminate corridors and stairways.

Super Bright LED TapeSome flexible LED tapes are already available and retails at about AU$60 per metre, for 60 LEDs consuming 4.8W total. The strip has a self adhesive backing and operates on 12vdc. The tape is also sold in 50 metre rolls and is likely to be much cheaper in that form. However, this tape has a 120 degree viewing angle, so would scatter too much light and cause glare when used on a ceiling. Also it is perhaps a little too flexible for easy installation in long strips.

See also:


Wednesday, December 26, 2007

Computer screen mounted desk lamps?

Philips Ambilight TVPhilips "Ambilight" range of flat panel TVs have lights around the edges and on the back. The light level and color is automatically adjusted so the lights match the brightness and colour of the image on the screen. This is claimed to reduce eyestrain. If this works, perhaps the same technique could be applied to desktop LCD computer screens. Apart from reducing eyestrain, this might be a way to provide very power efficient lighting for offices, schools and homes.

The latest Philips "Ambilight" range of flat panel TVs have a translucent bezel around the screen with colored LEDs in it. These are adjusted to blend with the image on the screen. Perhaps the same approach could be taken with LCD screens in offices. A row of LEDs could be placed around the display. These would be automatically adjusted to suit the image on the screen and the room lighting level.

A much simpler approach would be to have some holes in the enclosure to let out some of the light from the back light of the LCD screen. Some Apple notebook computers illuminate the logo in the lid this way: the logo is made of translucent plastic, allowing the backlight to show through. Using this approach the lighting would not change color or brightness with picture content, as the Phillips system does, but would automatically change brightness in step with the backlight.

Both LCDs and the fluorescent back lights used in LCD panels are very efficient. If the lights on the screen could replace some (or all) of inefficient incandescent room lights, this would save on power. Lights on the screen could be powered from the screen power supply, from the computer or from a separate mains supply.

Of course, placing lights on the screen is contrary to usual recommendations for office lighting, which have the light at high intensity, above and behind the desk. However, these recommendations were developed at a time when office workers read from paper flat on a desktop of several square metres. These guidelines may need to be revised where an LCD screen and keyboard is used for most work, with a desktop area of one square metre or less

Lights on an LCD screen should be sufficient to illuminate one square metre or so of desktop used around it. This would be enough to see the keyboard in front of the screen and some paperwork on either side, plus use the telephone

An adjustable low power fluorescent or LCD task lighting, might be used to supplement the screen light. This could be USB powered, or from the screen or computer power supply, to prevent having to provide a separate mains power supply.

Low power room lighting

If each desk is provided with general and task lighting, then the room light can be lower. The room need only be bright enough to allow people to see their way around and prevent glare. This could be achieved by using low wattage LED or fluorescent lights which double as emergency lights. This could be used to lower the installation and running costs of the lights.

Offices are commonly equipped with two lighting systems: a high brightness mains powered one for everyday use and a low voltage battery backed system for emergency use. The mains powered system provides reading level light everywhere in the office. The emergency system provides only enough illumination to find your way to an exit. The emergency lights need only operate from batteries for a few minutes and so need not be efficient or provide glare free lighting.

The standard room lights could be replaced with efficient low wattage fluorescent or LED lights, designed to provide a comfortable level of illumination for general office use, but not bright enough for reading or close work. Some, or all, of these lights could have battery backup, so they would also be used as the emergency lights. The new lights might be retrofitted into existing fittings. Very small LED and fluorescent light fittings can be added to the existing ceiling surface or suspended from it. The lower power required would also allow less cabling to be used, lowering the installation cost.

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