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ArcticMyst Security by Avery

My little collection of flashlights

Joined
Sep 20, 2013
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17,220
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It really depends on the flashpoint but thats usually not true. Most LEDs have a max Tj of way below 150°C which is no where near enough to burn anything.
LEDs can put out a huge amount of light so even though their emitting area is huge, they can still be used to burn stuff.


That really depends on what led and optic is used, High power phatlight or puny 3w cree xpg?
We could start calculating things, physics states: Conservation of etendue.

You can focus leds to even smaller spots than their emitter size area, it just depends on your optical system.
However you will decrease depth of field doing so.
Its a simple matter of beam parameter product, exactly the same thing that governs the focusabillity of lasers.

Yeah, I would expect you to try to change what I said as physically impossible, but that simply is'nt the case. You seem to think that powerful LEDs can burn at a distance. Proof it!
 





farbe2

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Oct 3, 2018
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Yeah, I would expect you to try to change what I said as physically impossible, but that simply is'nt the case. You seem to think that powerful LEDs can burn at a distance. Proof it!
Challenge accepted.

Red Led out of the known projectors
led.jpg

led1.jpeg
led2.jpeg

zYunHELKfrT0Rqsi4oDDPhA0HD42W_g-LsY98HIMzWBXQSKXAyJsY7Ndcq6p3SFDsnxZzXEaikHbwHXoaQ0pRy4DbbgffqnnXEBDfbu2k6c


That's just a 50W led an old red one. Not very efficient. A higher power and newer (smaller emitting area) led would be much better.
Also: my lenses are shit, just a random assortment I had laying around. Optimized ones would be better.

Distance is just shy of 1m, didn't have more room on my desk. Many more meters are possible. Same principle as a laser: Expand the beam to lower divergence, and focus it down again.

Due to the high NA source, big lenses are needed.

Show me a single datasheet of a led that can run at junction temperatures high enough to exceed the flash point of say wood.
Flash point of wood should be around 300C.

Also: the Halogen flashlight that "just gets hot" ... Radiated heat is also just light of a different wavelength.
 
Last edited:

CurtisOliver

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Lasers are coherent and can be focused more tightly. For an LED to burn it would require a lot of optical output.
Just so you are aware. This qualifies for the last sentence of my point. Photons are photons. However the coherency has a huge impact on the ability to maintain a power density great enough to burn.
 

¸¸¸

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Just so you are aware. This qualifies for the last sentence of my point. Photons are photons. However the coherency has a huge impact on the ability to maintain a power density great enough to burn.
I take note, I understand
 




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