high brightness leds

[hb leds]

my project title is " evaluation of HB LEDs & comparison with CFLs"
in this project m required 2 measure the intensity of different hbleds,making there V/I curves & ploting there efficiency as well.m using a lux meter 4 it. In my set up, i ve used a pipe & 4m inside i ve sprayed silver paint 2 make it a reflective surface,on 1 side of pipe i ve attached the sensor of lux meter & on the other side of pipe led is attached with an aluminium lid.nw a series connection is made which consist of power supply(dc), switch & this pipe setup. value of current is changed 4m the power supply.when switch is on,led is on & voltage,current & intensity is measured. the problem is that leds get heat up & effects the readind of intensity.also at the end of the project i ve to compare & replace CFLs with leds &ve 2 make a bulb of leds 2.i need help how 2 catter this heat issue, that by the end i can say in front of my panel dat leds cn replace CFLs & they produce negligble heat,gud brightness........plz xplan in detail n mention that wt sort of setup shud b made.

 

[rmain1972]

Please use proper English. Your post is hard to read. You'll get a better response if you do.

 

[carbonzit]

Amen. No "text speak". Use ... words.

 

[hb leds]

hb leds

my project title is " evaluation of HB LEDs & comparison with CFLs"
in this project i am required to measure the intensity of different hbleds,making there V/I curves & ploting there efficiency as well.I am using a lux meter for it. In my set up, i have used a pipe & from inside i have sprayed silver paint to make it a reflective surface,on 1 side of pipe i have attached the sensor of lux meter & on the other side of pipe,led is attached with an aluminium lid.now a series connection is made which consist of power supply(dc), switch & this pipe setup. value of current is changed from the power supply.when switch is on,led is on & voltage,current & intensity is measured. the problem is that leds get heat up & effects the readings of intensity.also at the end of the project i have to compare & replace CFLs with leds & have to make a bulb of leds too.i need help how to catter this heat issue, that by the end i can say in front of my panel that leds can replace CFLs & they produce negligble heat,good brightness........please explain in detail and mention that what sort of setup should be made.

 

[rmain1972]

Thank you for rewording your original post. If you are going to turn a copy of ypur post then you are using the wrong 'there.' You should use 'their.'
Also not sure what 'catter' means. Are you missing a resistor to limit the amount of current going to the LED?

 

[audioguru]

Some cheap "high brightness" LEDs are simply dim ones in a case that focuses and concentrates the light into a very narrow beam.
But a fluorescent light spreads plenty of light all around.

 

[ronsimpson]

You have a good power supply. When testing LEDs remember they are current devices not voltage devices. Set the voltage about 2 volts higher than you need. Short out the supply and set the current limit to the current you need. (100mA) Now connect the LED. Adjust the current limit knob to adjust the light output. The voltage and current can be read from the supply. Keep the supply in current limit mode.

LEDs act different whem hot. Make your measurements fast! Normally high power LEDs are mounted on a heat sink. I don't think you can get good readings with out a heat sink!

 

[ronsimpson]

I think you want to measure the total light output of your LEDs and CFs. Most people shine the light on the meter and think they measured something. They only mesured how well the lense on the LED works. I can get the same LED silicon with a 180 degree lense and a 15 degree lense. The light meter will read that one is 100 x better. Total Luminous Output may be expressed in candela or in lumens. This is a measure of the entire light output of the light sourse regardless of beam focus.

Using your silver tube is a good idea. Here is a picture of what I use. My first one was made from a glass ball about one foot across that was a light fixture. The inside is painted white. The meter looks in from the side. The light must not directly shine on the meter.

 

[hb leds]

hb leds

i am not using resistor because i am limiting my current,i am varying current myself in a manner as mentioned by ronsimpson.

in addition to this,the leds that i have purchased from the markrt are not cheap,they are quiet expansive.(reply to audioguru)

ronsimpson,thank you for so much help, iam using my power supply in the same manner as you have mentioned.nw my next question is that i am using this lid of aluminium as heat sink.in addition to this i am also using heat sink paste to attach led with the lid. but by the end i have to make a product out of it,which will remain on for a long period,how will i overcome haet in my end application?
i also want to know that out of all the hbleds,which led has the best efficiency? i have to compare it with the leds available with me.

 

[hb leds]

hb leds

i am not using resistor because i am limiting my current,i am varying current myself in a manner as mentioned by ronsimpson.

in addition to this,the leds that i have purchased from the markrt are not cheap,they are quiet expansive.(reply to audioguru)

ronsimpson,thank you for so much help, iam using my power supply in the same manner as you have mentioned.nw my next question is that i am using this lid of aluminium as heat sink.in addition to this i am also using heat sink paste to attach led with the lid. but by the end i have to make a product out of it,which will remain on for a long period,how will i overcome haet in my end application?
i also want to know that out of all the hbleds,which led has the best efficiency? i have to compare it with the leds available with me.

 

[hb leds]

hb leds

no one answered my questions yet..........i am waiting

 

[ronsimpson]

What question?
What LED to use? I thought that was your job to find out.

or

How to get the heat out? There are apps notes on how to do that.

 

[hb leds]

hb leds

all i wanted to know is that which led is best in efficiency vise,means in lumens/watt
? can any body answer it? because that efficiency will serve as a standard for my rest of the leds that i am testing.

 

[ronsimpson]

What LED??? What answer changes every month. New parts all the time.

 

[carbonzit]

That's not a simple question. It's not as if someone here would even be able to give you a definitive answer, like "model XXXX LEDs from manufacturer YYYY are the highest efficiency". You really are going to have to do some research here on your own. What kind of LEDs are you looking for anyhow? is this for illumination purposes (as in LED light bulbs as opposed to little blinkiing lights on the panel of a piece of electronic equipment)? How much light (how many lumens) are you looking for? What's the power source? form factor of the LEDs?

You can see that there are a lot of variables here, and since there are about a zillion and a half LEDs available on the planet (and, as Ron points out, new ones are continually coming onto the market), you really need to narrow down your search at least somewhat before we can really help you.

Can you give us some more details?

By the way, before you become invested too far into your search for high-efficiency LEDs, you might want to read this article ("The LED's Dark Secret" from the IEEE, not from some Internet rumor-mill) about, basically, why LEDs are not ready for prime time in terms of replacing CFLs and incandescent bulbs for lighting. Turns out that LEDs hit a brick wall efficiency-wise above a certain size and fall far short of other lighting technologies, like CFL, in efficiency. This problem, of course, is being worked on, but hasn't been overcome yet.

 

[ronsimpson]

Also think about price. LEDs are sorted. The very best are pulled out and sold for more money. Last week I found for $1.00 less we can get parts the are only 90% of the light. Your eye can hardly see the difference.

 

[carbonzit]

So Ron, at the risk of falling into the same trap as the O.P., what's the best place to get super-bright LEDs? By which I mean what Digikey classifies as <75mA devices (I'm actually more interested in the 20-30mA diodes), 10,000 mcd or better. And I'm interested in those "seconds" you mentioned. Hell, our eyes can't even really detect a 30 or 40% change in brightness, let alone 10%.

The biggest "bang for the buck" I've been able to find so far, in the category I mentioned, are these LEDs from Digikey: 18,150 mcd, 20mA @ 1.9V, standard T 1-3/4, $.67/ea (Q1). Can you top these? (Surplus/"grab bags" are OK.)

Whoops, thems are red. I meant these white ones, 28,200 mcd, 20 mA @ 3.2V, $.53/ea (Q1: at Q100 they're 41 cents apiece).

 

[audioguru]

The LEDs are very bright because the viewing angle for the red one is focussed into only 8 degrees almost like a laser beam. The white one is focussed into a 15 degrees spot light. If they doesn't shine directly at you then you might not see anything.

A good bright LED has a wide viewing angle. My solar garden lights shine about 140 degrees. The light is spread around so the brightness number is less.

 

[ronsimpson]

I do like Cree. I have not used these little LEDs for a while.
There are 5 types. BA, BB, CA, CB, DA for light output. DA is big $.
There are 6 types for voltage.
There are many different colors, and colors of white, and each of those have sub-colors.

If you order a BB 2A W3WM then there is a price.
If you order BB or CA, any voltage, W3 (any sub-color) the price and delivery will be much better. If you only want 100 then this does not matter. If you want 100 reals of 5000 then sorting is a problem.

AudioGuru is right. Don't get fooled by "brightness" and degrees of light output.

 

[carbonzit]

AudioGuru is right. Don't get fooled by "brightness" and degrees of light output.

So how do you measure brightness? (Obviously, not with a light meter ...)

Digikey gives a parameter called "Luminous Flux @ Current - Test", whatever that means, and it's measured in units of "mlm" (???). There's no measure for my white LEDs, and the reds are said to be 500 mlm. Do you now what this means?