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Old 23rd January 2008, 02:31 AM   #1
JinMTVT is offline JinMTVT  Canada
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Location: MTL
Default indoor lighting test with LEDS(pics) + need info on dimmers?

I have ordered a few expensive pieces of LEDS
from Seoul Semiconductor
wich are AC 120V driven direclty
( there are a 2 resistors on the pcb though )
I believe that they use the up and down of the AC
to drive and reverse/drive 2 different 1W section of the LED pannel, something like that ..quite simple
and that removes the complexity associated with LED electronics and voltage requriements ...

So that said , i now have 10 6500K
( was the only one avaiable by then) 4W ( 2 2W leds on each pcb ) "specialist" Acriche LED units @ 21$USD each from
I will be receiving some 3000K version of the same leds this week for further analysis.

My point was to test the usability of leds for indoor lighting to replace annoying CFL bulbs and plain ridiculous incandescent light bulbs.

So i tried to compare them to what was available at the moment in my house to see how they could be used.

Here are a few samples of the tests i did for the interested of you.

1- 6X4W LEDS 6500K ( total 24W )dispersed on the ceiling VS 1 phillips daylight 27W CFL ( quality one @ 5500K)

Please do not mind the color temperature difference, i tried to attenuate it by using automatic white on my camera ....the camera was setup to give the best exposure that represented the actual scene as seen with my eyes.


24WLED "star" setup
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Old 23rd January 2008, 02:38 AM   #2
JinMTVT is offline JinMTVT  Canada
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following test was done at kitchen
2 led modules for 8W total were used VS
2 50degree halogen 50W spots
( please keep in mind here that the leds are 110degree patern, so there is no bright spot as seen with the 50degree spots ... thought i do not see it would be a problem if the leds were recessed in a cone spot enclosure be tested )

2 50W halogen spots 50deg.

2 4W acriche led modules

Now this test is again 2 4W acriche led module VS 3 30-40W candella type incandescent in a round mount under a diffusing white glass ornment

i'd say that the total light output was a little higher with the 2 leds than with the incans here ..

incandescent lighting

2 4W LEDs

Again do not take care of the color temperature..
only brightness and illumination is in test here

I like what i've tested, and i will be investigating those new LEDs again much soon,
as i intend to use them in 80%+ of my future house lighting !!

What do you think ?

have you personally done tests with leds?

i know there are many more efficient modules,
but none has the retrofit possiblity and the easiness of those 120V AC units ..
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Old 23rd January 2008, 02:41 AM   #3
JinMTVT is offline JinMTVT  Canada
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Now onto the dimming subject ..

how do regular dimming control works ?

what do we want to control those leds?

i've read that LEDS are current driven units,
but they regulate their current depending on the feeded voltage not know if those are of the same...

I'd very like to be ablet o test those leds with some dimmer, i'll try to purchase one this week end at the store to see how it works wiht the leds.

i've also read that some dimmers work by switching on/off at different speed so there is no power loss from dimming .

my ultimate goal is beeing able to use those leds with regular Z-Wave dimmers to setup automation correctly

neway, any info on dimmers for lighting will be appreciated!
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Old 23rd January 2008, 03:36 AM   #4
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LEDs are usually powered by DC. Dimming is done by PWM of the DC power source. Without knowing more about those LEDs, it is hard to say what to use for dimming.

It looks like the LEDs aren't nearly as bright as your other test lamps. You may need more than the one's you tested with. If you calculate the cost of light bulbs and the electricity to run them and compare it to the LEDs, I think you'll find the break even point of LED vs incandescent is on the order of 200 years or so. LEDs are just too expensive right now to make economical replacement of incandescent or CFL. Of course, there's something to be said for being the first guy on your street to light his house with LEDs.

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Old 23rd January 2008, 03:50 AM   #5
JinMTVT is offline JinMTVT  Canada
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I do not have any interest in showing off my stuff...
so beeing the first guy in the hole province to use LEDS as main lighting doessn't matter much to me.

We pay around 4$ for thos 50W halogen spots..
wich are usually on from 5pm to 11pm on most days
We've been here for 6 years now,
and i can remember to having changed them at least 2-3 times each ..

that + the fact that it is 100W VS 8W
even if i'd throw in another LED for the spots, would probably be a bit brighter than the halogens...still be only 12W ..

now i know that there isn't much economy here,
+ the elctricity is damn cheap here in Quebec ...
but the form factor ( even with a cheap lasercut+stamped aluminum basket for heatsink/mounting... ) wich is pretty small if you ask me,
and the fact of not having to change a single bulb ever...

then, they are sellling for 20$ now ..probably around 12-13$ by the next 6 months..maybe 10$ in 1 years

The kitchen test is kinda fouled because the angle of the light is not comparable at all ..
i'f i'd be to use a collimating lens to something like 50-70degree just like the 50deg for the spots,
you'd see another picture here

the leds were lighting up stuff way further than the spots here, but the light on the countertop itself was alot less bright ...

the for the bathroom test VS incan...
well the leds were actually lighting up more than the regular bulbs, and the light was more equally distributed.... to be seen with 3K ones, since they are supposed to be alot dimmer.

then government is trying to pass a law here,
so that no incandescent are allowed within 2 years

I will not design my house lighting for a 2 year spawn,
and unfortunatly, CFL doesn't have anything other than efficiency that i want as lighting.

I'll try to dim the leds with TRIAC dimmer this week if i can find see how it reacts to it!
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Old 23rd January 2008, 04:35 AM   #6
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I have been curious about these myself.
"wich are AC 120V driven direclty
( there are a 2 resistors on the pcb though )
I believe that they use the up and down of the AC
to drive and reverse/drive 2 different 1W section of the LED pannel, something like that ..quite simple"

if this is indeed true (which is how it has seemed to me at first glance) AND these are good light quality, design, built, etc... then this is an elegant solution. Simple is good.

The problem I can see you may have with dimmers is that you may begin to visibly see the chopping. LED's have fast response, and any breaks in the power may become visible. -- As you point out, these work by having one light always on each half of the cycle. Persistence of vision will get part of the way, but the dimmer may break this down further. I may be wrong. They may switch fast enough... (or there may be other tricks at work in these "bulbs") similar to new 120Hz LCD TV's and issues around such...

For proper brightness control you might need a more linear control of the voltage or current. Current limit with increased resistance for a given voltage, or lower the voltage. So likely you could use a variac (or fast PWM), or a big potentiometer. (for the latter, you may need to experiment, or determine the R's in the lights now and calculate a bit) -- edit note: that is big, as in W not necessarily big R for the pot ;-)

?? can't wait to hear some of your results ;-)
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Old 23rd January 2008, 04:44 AM   #7
JinMTVT is offline JinMTVT  Canada
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the current dimmers seems to work with the Triac method, and it seems to operate @ 120hz

i do not believe there is any problem with the switching on/off action used on a LED
would have to contact SeoulSemi for that one i guess

there is no point if the leds fail after only a part of their minimum lifetime

there is a description on one site,
that said that those leds work as if there was alot od diodes onto each other until it made for 120V
and then there is another batch for the reverse AC wave
not too sure if i understand it

The light output from the 6500K pure white version is good..but the color temp is really bad
and the CRI is only of 70

the 3000K i have ordered, have a 92CRI
wich is just about the best u can get from most quality light sources ...

i also thought about the led rise and fall time,
i'll have to test it out i guess!

I have to understand how the latests Z-wave dimmer works, so i can see if it is the same or not,
and if we can use those for the leds...not much information on the net about the internals of such products though !
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Old 23rd January 2008, 12:09 PM   #8
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PWM dimming of LED's may cause video rainbows if the rate is to slow. I know that some expensive cars on their tail-light / brake-light combinations. On a dark curving road they video rainbow, well it's more like a strobe.
Video rainbow is a term used when a projection TV (front or rear) with a color wheel has a momentary rainbow like flash.
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Old 23rd January 2008, 02:45 PM   #9
soongsc is offline soongsc  Taiwan
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I wonder whether some good motion sensors well located to turn off lights when no one is there and turn on automatically when people move would be a better energy saver. Also wonder about solar power versus LEDs for continuous lighting.
Hear the real thing!
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Old 23rd January 2008, 04:15 PM   #10
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In making calculations of economics beware of the supposed 50,000 hour lifetime claimed for LEDs. They still claim 5-7 year life for CFLs but I have never had one last more than 2 years.

Those lifetime specs for CFLs and LEDs are based on very critical application specs- they must be on continuously, temperature must be in a specific narrow range, etc., all unrealistic of real-world use. The botom line is the marketing guys lie about these things in order to sell more of them.

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