LEDs, yea or nay?

[ELA]

Bob in all honesty it has been about a year since I last visited LED's, so I am open to the idea they have improved considerably.

Now with that said the manufactures play a lot of game with LED's rating especially efficiency. They flat out misinform.

One when they state the lumens/w they do not include the driver power consumption. LED's are current devices. If the driver is a shunt linear regulator current in = current out. So if the source is DC say 12 VDC and the LED is rated .35 amps at 3 volts for a 1 watt lamp, the driver uses (12 volts - 9 volts) x .35 amps = 3.15 watts. So now that 140 lumens per watt turns into 140 / 4.15 watts = 34 lumens per watt. A plain ole incandescent bulb can do that.

So if someone got some credible info I would like to see it.

dereckbc,
If a manufacturer of LED products wanted to make their products inefficient then they would design using linear regulators. None I have looked at recently use linear regulators.

They use PWM current regulators.

One in particular that I have tested ran at 24Vdc and measured 0.45A RMS for an "appearant" input wattage of 10.8 watts. Each of 4 LEDs consumed approx 0.8 watts for a total "appearant" wattage of 3.2 watts.

If you look closer however the voltage waveform at the LEDS is PWM and thus the voltage across the actual LEDS is only present for about 1/3 of the time (on this unit tested). Thus the wattage that is consumed is much lower than the simple "appearant power" calculation leads you to believe.

 

[dereckbc]

They use PWM current regulators.

PWM is still a serial device where input current = output current. Like I said it has been a while since I last took a look. I have seen some designs that use a buck-boost DC to DC converter, or a true switch mode converter, but even with those the efficiency is only as good as a CFL lamp which is still poor IMO when compared to say T5 or T8.

PF is not an issue for a utility supplied AC, but a big issue for off-grid solar battery systems. Like I said I think LED's will become mainstream in the near future, I am not convinced that that time has arrived yet. But I am open to reading up on the latest products and changing my mind. So if you got something please share.

 

[ELA]

When your talk is about linear regulators then

I am open to reading up on the latest products and changing my mind.

Suggest you do that ...

 

[randy263]

An interesting bit of lighting history... When electric light was introduced, many critics said it would never replace gas light because it was too harsh, too much glare, not a flattering quality of light, etc. Okay for special situations, but not for general lighting, where gaslight would always remain the standard.

 

[mengelman]

I recently replaced some xenon undercabinet lighting with led's against my recommendation. Both made by Kitchler. I had to admit I was wrong when it was done. Nice color and brighter than xenon. Plus no heat at all. Made me a believer. Still not convinced about room lighting.

 

[ofourcobra]

There is a rotary near my house where they installed new street lights, and for some reason they recently changed half of them to LED. I must say seeing them next to a metal halide the LEDS were brighter

 

[LarryFine]

An interesting bit of lighting history... When electric light was introduced, many critics said it would never replace gas light because it was too harsh, too much glare, not a flattering quality of light, etc. Okay for special situations, but not for general lighting, where gaslight would always remain the standard.

Critics also said nobody would ever need more than a 10 meg computer hard drive. :roll:

 

[bluesmoke...oops]

or that the computer would never be small enough or affordable for personal use.

 

[ActionDave]

There is a rotary near my house where they installed new street lights, and for some reason they recently changed half of them to LED. I must say seeing them next to a metal halide the LEDS were brighter

Our city changed out a bunch of street lights to LED and they are brighter at the lamp but they don't throw a beam as bright down at street level as Metal Halide.

Why is that? What is different about LED light?

 

[zbang]

The MH lamp produces it's light in a relatively small area which is easily focused by a lens or reflector. An LED fixture might use 20 or more LEDs to produce the same output but those are spread over a much larger area, so it's harder to direct that light. Think of it this way, 20 candala of light from a 1/2" square space or 20 1 candala sources spread over 2" square (those numbers are entirely made up). The larger the source, the harder it is to direct and focus. (This is why things like motion picture projectors use arc lamps- lots of output in a very small space. Much easier to focus into the right place.)

 

[ARORAED]

LED's are here to Stay!

LED's are here to Stay!

I designed them for the Philadelphia Intl. Airport Cell Phone Parking Lot and they came out beautiful, client is very happy. It's been almost a year and they still look and working great! LED's don't last 10yr maybe 8. Even though the LED's may last 50,000 to 100,000, it's the driver that you have to look at. The costs have been nose diving and if you get them from a reputable company, there is nothing to fear.

 

[Limart]

LEDs are quite good enough for striplights and some types of fills. Been using them for a few years, now. It's really nice to get completely variable color on a cyc with the dmx-controlled units. Where LEDs aren't good enough is lights that need a good pattern (ERS/"leko"/pattern spots). I expect those will be incandescent until the LEDs are smaller or somebody comes up with a condenser assembly to go with a bank of LEDs.

Just an FYI: There are a few LED profiles on the market now, all of which were exhibited at the LDI tradeshow this year and all of which were able to take patterns and take shutter cuts. None of them are very bright, still only for smaller venues, but "maybe next year?".