Hot sun, parabolic dish = Fried LED?

I was out the other day comparing a bunch of my warm tints and incan lights to natural sunlight and I was looking at the LED. I could pretty easily get the suns rays to concentrate on the LED die surface and make it glow bright yellow from the concentrated sunlight. Bright enough to over-expose the image below.

hypothetically can I damage the LED from doing this? I know parabolic dishes and lenses on a hot day can be used to ignite tinder, bugs...etc.

thanks in advance!!

Now you know what diffusers are really made for.

Nap.

I've seen videos of people cooking food with parabolic mirrors and huge magnifying glasses... from their comments and how fast the pan got smoking, I'd say there is a chance, but it might take more than a minute with a small reflector and an LED that was designed to handle some heat.

Worst case scenario for the suns insolation is 1kW/M^2, or .1 W/cm^2. Assuming a 30mm parabolic reflector, thats 7 square centimeters, or only .7 watts. If it was over the whole face of the LED that's probably fine. If the parabola concentrates it to a point of light... not so fine.

I wouldn't think the focal point of the reflector would be right on the led. If it was, yeah you could fry it in seconds. But if you think about it, have you ever seen or can you even design a parabolic reflector that puts the focal point BEHIND itself?

badtziscool said:

I wouldn't think the focal point of the reflector would be right on the led. If it was, yeah you could fry it in seconds. But if you think about it, have you ever seen or can you even design a parabolic reflector that puts the focal point BEHIND itself?

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great point there...

Which light has a whole parabolic reflector with the LED placed behind it?

badtziscool said:

I wouldn't think the focal point of the reflector would be right on the led. If it was, yeah you could fry it in seconds. But if you think about it, have you ever seen or can you even design a parabolic reflector that puts the focal point BEHIND itself?

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It depends. The focal point of a paraboloid is coplanar with all points on its surface that are at a 45 degree angle to the base. So if the reflector is a complete paraboloid, the focal point can't be behind it. But the reflectors for flashlights are truncated paraboloids (to allow the LED to poke through). If the reflector meets the PCB at a steeper angle than 45 degrees, the the focal point is indeed behind the LED. I don't know whether this is done in practice, but that's the math.

CKOD said:

Worst case scenario for the suns insolation is 1kW/M^2, or .1 W/cm^2. Assuming a 30mm parabolic reflector, thats 7 square centimeters, or only .7 watts. If it was over the whole face of the LED that's probably fine. If the parabola concentrates it to a point of light... not so fine.

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your calculation is correct.

a 50mm reflector would already collect 2 watts.

with an OP reflector I'd think that the light is not focused as precisely and the LED is probably going to survive for some seconds/minutes depending on how big the reflector is and how good heatsinking is. A high-power XM-L light would probably survive longer compared e.g. to a XR-E with a similar sized reflector since the first should be designed to dissipate more way power.

With a big, smooth reflector it is probably not a good idea to do this even for a few seconds, depending on how good the reflector is.

Running the LED at max power would create additional heat, obviously speeding up the process.