| [GMCnet] More on LED lights [message #158078] |
Thu, 26 January 2012 10:51  |
glwgmc
Messages: 1014
Registered: June 2004
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Several people have emailed off line requesting more info on how to select "the best" LED lights for our coaches. While I can't answer that question directly, perhaps this will help a bit.
One would need four things to make an informed decision based only on the specs; a) price, b) light output, c) current draw and d) details pertaining to things like build quality, operating voltage range, effectiveness of heat sinks, etc. Unfortunately, only price is readily available and consistent across manufacturers/repackagers. Expressions of light output are easily gamed. Some measure the theoretical light output of the emitter itself while others measure actual light output at some distance from the emitter. Think of those measurements as the total amount of light available. Only a rare few measure the light falling on an object a certain distance away from the emitter/fixture (like the book you are trying to read) and that is what you really want. That tells you how much light is available per unit of area covered. If you concentrate the light (think spot light) you have more light but only available over a small area. If you diffuse the cover over the light s
ource you can spread the light out but will have less of it at any given point in the light field. The first measure (total amount of light available) is called "lumens" while the second measure (light available a given distance away over a given area) is called properly called "lux". Technically one lux is one lumen spread over one square meter. Confused yet?
Well, think how easy it is to game these measurements to make you think one LED is "brighter" than another. Since there are no standards you have to take with a grain of salt all the marketing hype about how "mine is brighter than yours". Nope, you cannot simply look for the most lumens per dollar 'cause that won't tell you much unless you know how the lumen measurement was taken in all instances that you want to compare.
Same is true when it comes to power consumed by a given LED replacement bulb or fixture. You will see lots of hype here, too. A quick scan of eBay or
Quartzite will bring up all kinds of flashlight ads that scream 5 WATT LED, or even 7 WATT LED. Must be way brighter than a measly old 1 watt LED, right? Nope. Maybe yes, maybe no. Like the shop vac marketing that shouts "6.5 PEAK HP" on a device that has 15 amp 120vac plug that couldn't draw more than about 2.25 hp running (they do this by telling you how many amps the motor can stand before burning up and then convert that number to something they call peak hp), the rated wattage is simply not a good measure of what you really want to know which is how much of my battery capacity will I use up with this LED turned on in my coach. I could rate my "7 WATT LED" as the amount of current you can pass through the emitter before it burns up - not a very useful measure. You cannot simply divide dollars by watts and say the one with the lowest cost per watt must be the best. It is too easy to game that making it meaningless to you trying to make a decision. Fortunately nea
rly all LED lights are so much more efficient than incandescent/halogen (~10X better) or florescent (~2x to 4x better) that all will be a great improvement.
Nor can you simply go by how many LEDs are in a given fixture or replacement bulb. More is not necessarily better. Some of the very best and brightest LEDs are single emitter units made by Cree (cree.com) but not all of their offerings are necessarily best in class. This is a world wide market with lots of good players.
So, if you can't rely on dollars per lumen or dollars per watt or number of LEDs, then what can you rely on. Answer, you have to look at several competing offerings, see which appear to be better to your eye and buy them only from someone who will allow you to return them for a full refund if they don't do what you want when installed in your coach. I don't know of any way around this "buy it and try" approach until some standards are adopted industry wide.
I have purchased LED units that are very good from several different sources including http://prudentrver.com, the units assembled in AZ (and the ones sold by Jim K and Dan G) as well as ones coming out of SEA, so place of manufacture is also not much of a guide to what will work best for you.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
541-592-5360
www.southernoregonguild.org
www.siskiyouguild.org
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Jerry & Sharon Work
78 Royale
Kerby, OR
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