LEDs - Fiberglass RV


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Old 11-05-2007, 06:28 PM   #1
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As I was sitting here waiting for some computer scans to be done I picked up the latest Auto Electronic magazine. I found this article on LEDs in automotive applications quite interesting. It's very technical, but should illustrate some problems that are currently facing the use of LEDs.

If there's an interest I'll pull some exerts and try to put the technical information into laymans terms.
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Old 11-05-2007, 07:07 PM   #2
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I'll bite Byron. I wasn't aware there were any problems with using the LED lighting, so would be curious to know what this means in practical and simple terms.
Appreciate the offer to simplify for us...
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Old 11-05-2007, 10:25 PM   #3
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OK, here, I hope is the short story. The italicized parts are my comments. The rest are direct quotes from the article.


Universally, automotive electrical supply systems are based on a lead-acid battery, which is charged by an alternator/regulator that is mechanically driven by the engine. Such a system suits older incandescent light bulbs, but not LEDs. A well-regulated current sup-
ply is necessary for optimal LED performance.

Apparently thereís some problems with using LEDs in the current electrical system.

As long as the battery voltage is constant,a series resistor performs adequately
for computer and instrumentation applications. But, automotive industry requirements mandate accounting for battery variations between8 V and 18 V and up to 80 Vpeaks. In addition, high-intensity LEDs generate substantial amounts of heat from the resistor. This makes thermal designs more difficult.

The standard resister method of controlling current has problems. Mainly because the automotive voltage isnít constant and steady. (My note: 80 Volt peaks are quite possible and all electric and electronic equipment on a vehicle must pass an 90 volt test. Itís not a steady 90 volts so donít try it.) Furthermore the series resistor will generate lots of heat that will need to be dealt with.

Red and amber LEDs of gallium arsenide (GaAs) and gallium arsenide phosphide (GaAsP) types have strong variations in light output depending on the junction temperature. Typically, an LED with a 100% light output at 25 įC will have only 40% output at 80 įC.

With the common type of LEDs as the temperature increases the light output will decrease.

Nearly all cars today employ red GaAs LED taillights. Consequently, most LED taillights shine too brightly in cold and dark surroundings and too weakly in hot and bright surroundings. The legal standards controlling automotive lights were established many years ago based on incandescent light bulbs. Incandescent light bulbs operate in a temperature range of several thousand degrees temperature of the heated filament light source. So the effect of an ambient temperature difference of 60 degrees (between 20 degrees and 80 degrees) on light output is hardly noticeable. Today, in cold weather it is easy to see the difference between taillights with LEDs vs incandescent bulbs. It is questionable whether the LEDs are too bright in cold weather.

The bottom line appears to be that LEDs are coming for automotive applications, but not quite there. Thereís still a lot of work to be done before they can become a standard.

My opinions.
From what Iíve observed on the road many LED tail lights are way too bright at night. I havenít noticed a lot of difference between LED tail lights and incandescent during the day time, expect the typical LED pattern. Again from my own experience, we build an LED display for road and air temperature. We had to go to considerable lengths to control the brightness. We had to put a light sensor in the display, (we werenít able to connect to the standard dimmer control) that would allow different brightness settings depending on ambient light. The darker it is the less light output. The high brightness would blind the truck driver if we were at the level needed during bright sun light. One might want to wait a couple years before jumping on the LED bandwagon.


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Old 11-06-2007, 05:57 PM   #4
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It appears that more models (2008) are now coming standard with LEDs and I have now begin to notice burned out elements in some of the first vehicles that used them. As with all technology, it will take some time to work out the bugs.

Do you think they will include a voltage regulator within the light unit to solve some of these issues?
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Old 11-06-2007, 06:04 PM   #5
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Do you think they will include a voltage regulator within the light unit to solve some of these issues?
Since there's more than just voltage regulation involved I suspect light output control will be done inside the vehicle. One controller can control both tail light for example. Using micro controllers all rear lights could be controlled from one controller and the front lights controlled by another.

Once there's enough usage and demand there will probably after market systems and can be put into older vehicles and towables.

That's my best guess at the moment.
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Old 11-06-2007, 08:48 PM   #6
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I have now begin to notice burned out elements in some of the first vehicles that used them.
My LEDs inside are also having random elements burn out. I may have to go back to using incandescent lamps.
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Old 11-12-2007, 08:03 PM   #7
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Thanks guys.

This is a timely discussion for me as I am getting close to ordering new tail-lights for the Boler and was going to go with the LED's.

I think that perhaps I should stay with incandescants then.
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Old 11-13-2007, 11:27 AM   #8
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I'm not having any problems with internal or external LED's yet. Internal LED's have been in use for over 7 months, LED taillights for two trips.
But I will keep an eye on them for any burnout of elements.
I wouldn't go any other way now in comparison to incandescents.
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Old 11-13-2007, 01:59 PM   #9
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If individual LEDs ("elements") of an LED lamp burn out, most of the rest probably keep working. Most incandescent trailer lamps take a single bulb - then that one filament burns out, there's no light. I'll take 9/10 of a working LED assembly over no light any day.

All new city buses here and many trucks have used LED lamps for several years. I haven't noticed a burned out one yet, although I'm sure there are some. I think they're doing pretty well, although of course they won't all reach the design life of 100,000 hours or so. By the way, has anyone towed a travel trailer for even one tenth of that time in its entire life?
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Old 11-13-2007, 02:48 PM   #10
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If individual LEDs ("elements") of an LED lamp burn out, most of the rest probably keep working. Most incandescent trailer lamps take a single bulb - then that one filament burns out, there's no light. I'll take 9/10 of a working LED assembly over no light any day.
Burn out is not the only problem with LEDs. There's still some work to be done on light output vs ambient light. (too dim during the day, blinding at night). There's temperature vs light output. Some of this has been some what worked out, but still a ways to go. If you read the article associated with the link above it'll explain it all.


Quote:
All new city buses here and many trucks have used LED lamps for several years. I haven't noticed a burned out one yet, although I'm sure there are some. I think they're doing pretty well, although of course they won't all reach the design life of 100,000 hours or so. By the way, has anyone towed a travel trailer for even one tenth of that time in its entire life?
Just yesterday I followed a dump truck with LED tail lights. It was cool day and lights were dimmer than an incandescent light and 1/2 of them had several LEDs out. There was 6 lights. My Blazer uses an LED bar for the high 3rd brake light. I had to have it replace because there only 2 LEDs still working.

I fully believe that at some point in the future LEDs will be the thing for warning lights. Early adopters are great because they fuel further development. Late adopters will reap the benefits the early adopters have provide through their generous financial help.

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Old 11-13-2007, 03:45 PM   #11
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Burn out is not the only problem with LEDs.
No, of course not. The article is very interesting reading, and I agree that there are various issues, but I was responding directly to the concern about "burned out" elements in this discussion topic.

Even with the intensity management issue, and even with some elements failing, the LED tail lamp assemblies which I have seen in my hour or two a day on the road are still more effective - in my opinion - than typical incandescents.

Specifically in the case of trailer lights, I would trust a typical LED unit (intended for trucks) to be working and to be visible, more than the current single-bulb Reflect-O-Lite units on my Boler.
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Old 11-13-2007, 03:49 PM   #12
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No, of course not. The article is very interesting reading, and I agree that there are various issues, but I was responding directly to the concern about "burned out" elements.

Even with the intensity management issue, and even with some elements failing, the LED tail lamp assemblies which I have seen in my hour or two a day on the road are still more effective - in my opinion - than typical incandescents.

Specifically in the case of trailer lights, I would trust a typical LED unit (intended for trucks) to be working and to be visible, more than the current single-bulb Reflect-O-Lite unit.
Do you have those LEDs installed in your trailer?
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Old 11-13-2007, 04:27 PM   #13
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As Peter mentioned in LED Light Nirvana, IKEA Puck Lights! and further explained in Reading lights-looking for 12V (non-halogen)-maybe LED'S?, he is supplying a set of LED lights with a regulated voltage, and the light assemblies incorporate series resistors. This appears to me to be exactly the "better, but not optimal alternative" described on the first page of the article, and it seems like a good solution for applications with moderate light output.

By the way, more LEDs are coming... the Audi R8 has some headlight functions via LEDs, and reportedly will offer a version with all functions performed by LEDs. You'll have to be alert to spot this setup: R8's are a rare exotic (I've heard there's one in Edmonton, but have never seen it). This is clearly a case of deep-pocketed early adopters.
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Old 11-13-2007, 04:32 PM   #14
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Do you have those LEDs installed in your trailer?
Nope. . The original lamps still work - as badly as ever - so I have not replaced them with anything. I have also resisted changing the original appearance of the trailer unless functionally required.

I mentioned the specific model of lamp because you need to see these dimly glowing things to appreciate how marginal they really are; they're the "wedding cake" lensed design with a flat "reflector" base.
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