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Author Topic: The LED lighting project  (Read 9523 times)
JohnEd
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« Reply #30 on: April 08, 2009, 03:42:00 PM »

I "built up" 6 of these beauties running off of 12.6 volts.  I didn't use a resistor but simply figured the voltage drops needed!  They all failed within a month.

Thank you, thank you, thank you.

John

PS:  Boogie,  You can give me information that I might possibly find help full wrapped in any amt of sarcasm, any degree of "talking down" or just plain rudeness you might see fit.  No need to parse your words, walk on eggs or consider my ego.  Let er rip.  SHOW ME THE MONEY,errrrr, give me the info.  Thank you for all the info you contributed this time and all the other times.   AND, that goes for the rest of you.

You are all going to come out of this as still beer drinking buddies and this place amazes me.

John
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Sean
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« Reply #31 on: April 08, 2009, 03:55:23 PM »

I've now had three out of eight of the Lights of America (professionally engineered) 110 volt LED bulbs fail.  ...  In addition one of the bulbs I bought from Sailor Sam's (at marine pricing) is intermittently going dim. 


Bob,

FWIW, I was an early adopter of the Truck-Lite LED tail lights (back when they were giving them a "lifetime" warranty).  Out of four turn signals and four brake lights, I ended up replacing seven lights within two years.  (The replacement models did not come with a lifetime warranty -- I think Truck-Light learned a lesson there.)

You will almost always get better quality by building it yourself.  I think the manufacturing tolerances were just too loose (and the packaging technology too new) for these items.  The circuit engineering was probably fine.

The LoA stuff, BTW, is particularly mass-market cheap.  Many complaints about them, including back when they focused more on compact fluorescents.  Any product can be cost-reduced to the point of unreliability  Smiley

-Sean
http://OurOdyssey.BlogSpot.com
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bobofthenorth
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« Reply #32 on: April 08, 2009, 04:25:07 PM »

I "built up" 6 of these beauties running off of 12.6 volts.  I didn't use a resistor but simply figured the voltage drops needed!  They all failed within a month.

You might want to look hard at what you did different then because I built 32 of them and none of them have failed.  And I use mine every day.  I'm not pretending mine are going to work forever - in fact after the flaming I have taken here I expect them to fail every night when I flip the switch on.  But so far they have kept on keeping on. 
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R.J.(Bob) Evans
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« Reply #33 on: April 09, 2009, 12:32:06 AM »

Bob -

Started reading this thread tonight, and didn't realize it until your update that it started back in February!

OK. . . so much for me paying attention - NOT!

OTOH, I learned something tonight about LEDs, which is what these message boards are all about - sharing ideas and solutions to the complex task of converting a coach.

So even if there were a few rough spots in the conversation, to me it was well worth it.

Therefore, thanks to you, Gary, Tim, Sean and the others who all contributed their share to this thread.

FWIW & HTH. . .

 Wink
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« Reply #34 on: April 09, 2009, 10:21:05 AM »

Bobn O N,

I don't know either.  So many variables: mfr, light, V rating, my being arithmatic and spelling challanged....who knows? Embarrassed Tongue Grin

I am going to build some more though.  What do you suggest for a source for the LED's.  I liked the idea of adding in some yellow light.  Unlike you, I don't care for that intense white light.  They must have different temps of white so that you don't have to mix colors.

Sorry about the flaming, really I am. 

Thanks,

John
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Sean
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« Reply #35 on: April 09, 2009, 11:26:47 AM »

...  I liked the idea of adding in some yellow light.  Unlike you, I don't care for that intense white light.  They must have different temps of white so that you don't have to mix colors. ...


John,

White LED's are not really sold by "color temperature" (although you could certainly calculate it).

It is, in fact, technically challenging to make a "white" LED.  Colored LED's are purely monochromatic -- they emit light of exactly one wavelength.  Since "white" light is a combination of many colors, yet the physics of an LED allow it to produce only one wavelength, white LEDs are made one of two ways:

1.  Combining three diode junctions in the same package, one Red, one Green, and one Blue, with intensities adjusted so that the output appears white.  These LED's are very bright, use a lot of power (relatively speaking), and are quite expensive.  If you wanted to build a lamp with, say, nine LEDs in it, it would be cheaper and easier (and you'd have a much greater degree of control) to use three blue, three green, and three red LEDs of appropriate intensity, rather than nine of this type of white LED.  Above nine LED's, you can adjust not only the intensity but also the number of each color LED to tweak the color temperature of the light output.

2. Using a monochromatic Blue junction or an ultra-violet junction with a yellow phosphor coating.  The light emitted by the diode is blue or UV, and the phosphor is excited by this wavelength and re-emits at a yellow wavelength.  In the case of blue junctions, the visible emission is a combination of the blue and yellow, making white with a bluish tint.  This is the most common (and least expensive) type of "white" LED.  Again, if you are going to make a multi-LED fixture, you can adjust the color temperature by adding red or yellow LEDs as needed.

The technology to generate broad-spectrum ("white") light from diodes is improving all the time.  Today's white LEDs are available much warmer than those of a few years ago.  When we built Odyssey, we put no LEDs in, other than some floor-level "night lights," because Louise absolutely can not stand the too-cool color temperature.  In our next home, however (which we expect, at this point, to be a boat), we may very well have a great many LED fixtures, because the color temperature will have improved (in some cases due to manufacturers simply slipping a couple of reds into the fixtures).

Hope that helps.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #36 on: April 09, 2009, 11:57:32 AM »

I am going to build some more though.  What do you suggest for a source for the LED's.  I liked the idea of adding in some yellow light.  Unlike you, I don't care for that intense white light.  They must have different temps of white so that you don't have to mix colors.


Hiteq LED source

That's where I got the ones I am using.  He seems to have changed his minimum lot to 1000 units - I was able to start out with less than that.  If you want a smaller quantity to play with contact me offline and we will work something out. 

I'll probably get shot down for the next statement but it appears to me that the voltage of the LEDs is a function of the colour output.  If that is true you might be able to use the voltage of the LED as an indicator of the colour of the light output.  But note: I never said that was true or a rule - its just something I have noticed and not pursued.
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R.J.(Bob) Evans
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« Reply #37 on: April 09, 2009, 12:02:00 PM »


 Bob,

    Can you get more of the boards you had made up?

 Thanks
 Skip
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« Reply #38 on: April 09, 2009, 12:23:12 PM »

I'll probably get shot down for the next statement but it appears to me that the voltage of the LEDs is a function of the colour output.  If that is true you might be able to use the voltage of the LED as an indicator of the colour of the light output.  But note: I never said that was true or a rule - its just something I have noticed and not pursued.


Bob, you are partially correct.

The light color depends on the underlying technology (read: semiconductor materials) used in the LED, and that same selection of materials also determines the voltage drop.  But voltage alone is not a reliable predictor of color output; a 3-volt part, for example, could be green, blue, violet, UV, or white.

There is a nice chart showing wavelength, technology, and voltage for most common LED technologies about halfway down this article:
http://en.wikipedia.org/wiki/LED

-Sean
http://OurOdyssey.BlogSpot.com
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Tim Strommen
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« Reply #39 on: April 09, 2009, 04:07:00 PM »

...  I liked the idea of adding in some yellow light.  Unlike you, I don't care for that intense white light.  They must have different temps of white so that you don't have to mix colors. ...


John,

White LED's are not really sold by "color temperature" (although you could certainly calculate it)...



Sean, that's not entirely correct... (I'll explain in a second)

Guys, just like every other product built out there - given the price and the quality of manufacture, there is a broad field for product reliability in any category.  If you buy a Yugo vs a Toyota, you can expect it to be cheaper and not last as long...

The same holds true for LEDs.  Different manufacturers have different processes, and different quality control schemes.  The brand that I most prefer (and use for all of my LED lighting projects) is Lumileds (now part of Philips).  They have been leaders in high power (not indicating) LED lighting for about a decade now.  This is the brand LED that lit up the "ball" in Times Square this past New Years.

They take lighting so seriously, that they actually bin their LEDs into like-brightness and like-color part numbers.  This means that if you buy a specific "bin" of their LEDs (even white), you can expect a high level of consistency between parts.  These are also the guys that found out that LEDs prefer a "soft-start" (a slow ramp up in voltage at startup) to prevent stress on the bonding wires (the little gold wire that connects the LED Die to the pins).

In addition one of the bulbs I bought from Sailor Sam's (at marine pricing) is intermittently going dim.  Usually if I slap it lightly or turn it off and back on it comes back.


This is indicative of a bonding wire that has burned and has an intermittent "open" between the Die and the pin (the rest of the wire is held in place by the acrylic packaging).  This is one of the three most common failure modes for LEDs: high-temp burnout of the die, and start-surge burning of the bonding wires, and finally discoloration (browning) of the acrylic near the die causing a severe drop-off in perceivable light output (this is considered a failure even thought the LED may appear to be outputting light still...).

What you mention above is exactly the kind of problem that Boogie, Sean and I have been warning about with cheap design and construction...  As stated previously, even the corporate jobs can have corners cut.

The store bought assemblies are always going to be more expensive (monetarily), since they have to buy parts, add the cost of building it for it to be profitable for them, then the reseller has to inflate the price so that it is profitable for them.  Usually the material cost is about 1/3 the final retail price.  The reason I like to build most of my electronics myself (other than a sense of accomplishment) is that I can spend more of the money I would have spent on a finished product - on the actual raw materials to begin with.

I buy Lumileds Brand "Luxeon" LEDs from Future Electronics (their website to be specific).  Each LED is about $1.50 to $4.50 depending on brightness and color.  They have most of the Lumileds "bins", which means that you can buy "Warm" 3100K (this is about the color of a halogen light bulb), "Neutral" 4100K (this is about the color of sunlight at noon), and "Cool" 6500K with different light outputs (from 8.2lm up to 200lm per LED), in several different package types (the "Luxeon Rebel" is my current favorite - it is physically the size of the "bump" on the + side of a AA battery, but puts out up to 180lm at 700mA for cool white).


The cost may sound steep, but remember that the part that is sold by "hiteq" is only 2lm (1850mcd w/75deg beam angle = 2.402lm {source = http://led.linear1.org/lumen.wiz}).  To match the light output of one of my $5.44, 200lm LEDs - you need to use just about 83 LEDs... (which works out to about $20 worth of the hiteq LED, and you need more space on the PCB to put more LEDs {bigger fixture}, and there are more points of failure, etc...).  Plus on the power side, the one LED draws 1Amp at 3.75V, where as 83 LEDs draw .02 amps at about the same voltage - figuring power at 3.75 x 0.02 = 0.075watts, an you have to multiply this by 83...  So it's 6.225 Watts for the hiteq part vs. 3.75 for the Lumileds Luxeon part for the same light output - which do you think is the better deal?


As I'm sure must be said, I am not compensated for talking about LEDs no matter what manufacturer... I speak my opinion for free and without influence. Wink

-Tim
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« Reply #40 on: April 09, 2009, 05:18:19 PM »


Sean, that's not entirely correct... (I'll explain in a second)



OK, Tim, second's up.  Please explain what you meant.  Other than Lumileds, who's binning their white LED's by color temperature?

-Sean
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« Reply #41 on: April 09, 2009, 06:50:53 PM »

Osram (they make the "Golden Dragon" LED)...

Wait a minute... I didn't think I had to come up with more than one!!!  Grin

The cheesy 20mA LEDs are not really the best for general illumination.

-Tim
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« Reply #42 on: April 09, 2009, 06:59:11 PM »

Osram (they make the "Golden Dragon" LED)...


OK.  But I note that folks like Vishay don't (although, if you hunt around, you might find most of their whites are 5500 Kelvin).

So I (mostly) stand by my statement.  Perhaps modified to read "white LED's are generally not sold by color temperature."  Yes, you can find them that way, but most folks buying parts from common suppliers will not find a selection of temperatures, or even published information on color temps for the parts they are buying.  FWIW.

I did see you said "not entirely correct" so I'll let you slide  Smiley

-Sean
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« Reply #43 on: April 09, 2009, 07:14:45 PM »

I did see you said "not entirely correct" so I'll let you slide  Smiley

Phew!  That was a close one  Grin

-T
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« Reply #44 on: April 09, 2009, 07:53:53 PM »

Tim...be careful here...I have read a lot of Sean's wifes comments in their blog...that girl is sharp...I will have to say I have Sean's back...I don't want her on mine! Grin
Just in case someone did not get the humor here...I am joking.
Actually I like the fact that there are two folk's here trading comments back and forth, one telling the other he might not be entiely correct and an all out war has not started!  And we are all learning something.
I am also tickled that after everyone said BobOfTheNorths lights won't work long...they still are! Grin
Jack
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