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Tesladownunder

Fri Apr 10 2009, 11:28PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

aonomus wrote ...

Try to light some black paper with the *unfocused* light, I'm sure with the right lens you could burn anything with 100W of power, but I'd be more amused at a unfocused burn.

Lets just think about that and compare that with a light globe.
First here is a very effective infrared filter with a sharp cutoff.

1239387103 10 FT66499 Led100wfilterirnoseethru

Then here it is in front of a silicon detector calibrated for 10mV/mW for the 5x5mm surface. The LED reads 9mV with and 425mV without the filter. ie only 0.5% of the LED output is infrared. If they are only 10% efficient, then light output is 10W in visible range only.

1239387103 10 FT66499 Led100wfilterir9mv

1239387103 10 FT66499 Led100wfilternoir425mv

So what about an incandescent globe (not Halogen). Well, if you run the detector next to the globe the meter reads 425mV (ie greater than the LED) BUT the level is 392mV with filter on. Hence 92% of the output is infrared (as opposed to 0.9% with the LED).
What this means is that the incandescent globe puts out much more total radiation but most of it is in the infrared. The globe radiates the heat whereas the LED puts it into a fan cooled heatsink.
So you are not going to burn things easily with the LED at all, focussed or not.

aonomus

Fri Apr 10 2009, 11:37PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Ah, I suppose its emission is fairly narrow then, forgot about them being blue + phosphor. Derp.

Shaun

Fri Apr 10 2009, 11:43PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Well, If you are measuring 42.5mW of light onto a 5x5mm detector a centimeter or two from the LED, you could theoretically do some focused burning. Of course optics to focus it would be a little tricky, and the object would have to be dark in color due to the presence of visible light only.

Tesladownunder

Sat Apr 11 2009, 12:52AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

aonomus wrote ...

Try to light some black paper with the *unfocused* light, I'm sure with the right lens you could burn anything with 100W of power, but I'd be more amused at a unfocused burn.

Prepare to be amused....

Well, I tried the obvious - black cloth on the unfocussed output. Here are the results in a sequence from switch on to 14 secs later.

Steve Conner

Sat Apr 11 2009, 08:29PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yikes! I guess you figured out that black things can be burnt by visible light too, it doesn't need to be infrared.

I wonder if there's some law of optics that limits how fine you can focus it, given that the light is relatively diffuse and coming from a large area, compared to something like a 100W short arc lamp.

Tesladownunder

Sun Apr 12 2009, 01:06AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Steve McConner wrote ...

Yikes! I guess you figured out that black things can be burnt by visible light too, it doesn't need to be infrared.

LED safety 101. Do not stand next to a LED with your remaining black tee shirt.

It will still have 10W+ visible output. A 10W laser would burn well mainly because it can be focussed so well.

Steve McConner wrote ...

I wonder if there's some law of optics that limits how fine you can focus it, given that the light is relatively diffuse and coming from a large area, compared to something like a 100W short arc lamp.

Something I have wondered about too. I have played with a lot of random lenses, spherical mirrors, fresnel lenses and glass sheres out of my optics box but have no idea what I am doing. The best performance was with a magnifier used for looking at skin lesions and I have bolted this to the LED. It is close and broad enough to capture a reasonable proportion of the light output as given by the light output curves.

FEATURES:
Long lasting (Last up to 100000hours), Low Power Consumption, Intensely Bright
More Energy efficient than Incandescent and most Halogen Lamps, Low Forward Voltage Operated, Instant Light (Less than 100ns), High ESD Protection (More than 3KV), No UV
Source Material: InGaN
Emitting Colour: White
Luminous Intensity: Min:6400 lumens Max:7400 lumens
Reverse Voltage:5.0 V, DC Forward Voltage: Typical: 32 V Max: 36V
DC Forward Current: Typical: 3000mA Max: 3500mA, Viewing Angle:160 degree
Lead Soldering Temp:260Â°C for 5 seconds
Size of led: 40mm X 46mm
led emitter size: 21.5mm X 21.5mm Viewing Angle:160 *Absolute Maximum Ratings at Ta=25Â°C:
Power Dissipation
Pd 125 Watt
Peak Forward Current
(1/10 Duty Cycle,0.1ms Pulse Width) IF(peak) 3500 mA
Continuous Forward Current IF 3000 mA
LED junction temperature JT 85 Â°C
Reverse Voltage VR 5 V
Operating temperature range
Topr -20Â°C to + 80Â°C
Storage Temperature Range
Tstg -30Â°C to + 100Â°C
*Electrical/Optical Characteristics at Ta=25Â°C:
Parameter Symbol Test Condition
Min. Typ. Max. Unit
Luminous flux Ñ„ IF=3000mA 6400 - 7400 Lumens
Viewing Angle 2Î¸1/2 IF=3000mA 160 deg
Forward Voltage VF IF=3000mA 32 - 36 V
Reverse Current IR VR=5V 100uA
Color Rendering Index Calculation Spm X 0.280 - 0.340
Spm Y 0.280 - 0.340
Correspondingly CCT IF=1500mA 5500 6500 7500 K

Tesladownunder

Tue Apr 14 2009, 07:27PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

OK 48h, new info double post.

Bicycle mount.
Firstly a comparison with my 3W bike light.
Second with the 100W LED mounted.
Third with the original bike light and the lights of a passing car.
Lastly the 100W LED with a passing cars lights.

1239737055 10 FT66499 Led100wbikeshedcompare

Mattski

Fri Apr 17 2009, 09:38AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Slashdotted!

Tesladownunder

Fri Apr 17 2009, 12:46PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Slashdotting took 50,000 hits (40MBit/s) and the 4HV server didn't falter. Was a time when only a fraction of that would bring it down. Well done Chris.
Got rejected by Neatorama but I will submit it to others.
If someone wants to submit it to DIGG, feel free.

A lot of Firefox viewers couldn't display it because of a table that I imported from eBay that worked in IE7 but not Firefox. OK now though.

Now I was waiting for another post to show my LED burning a CD Cover. More pics on the site.

1239972260 10 FT66499 Led100wcdcoverburnresultbest600

aonomus

Fri Apr 17 2009, 01:54PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

The slashdotting was probably mitigated since most of /. uses Firefox, and those without IE7 wouldn't load the images (thus saving alot of bandwidth).

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