Using LEDs with parabolic reflectors...

louieatienza

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So I want to make a small searchlight around 12" diameter... Been reading on focal points on parabolic reflectors. Is it necessary to mount the LED at said focal point? Would simply mounting the LED at the mirror aperture work? Or would a secondary reflector or lens at the focal point be needed? Thanks in advance for your help!
 

louieatienza

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I figured as such... But then since the emitter only throws in one direction, that would limit the size of the beam narrower than the actual reflector? Is there any way around that?
 

alpg88

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bare leds usually have 90-130* beam. reflectors are not the best for leds, tirs are. if you want a thrower get ledil seanna lens
 

BVH

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Simply that "reflectors are not the best for leds" is not always correct. Same with "if you want a thrower get ledil seanna lens" is not always correct.

The BLF GT could be added as an example of a very high performing led-reflector combination.
 
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louieatienza

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Thanks for the replies... Gadget lover, cool thread! BVH, you own some amazing lights, thanks for your insight. I just picked up a BLF GT and very happy with it - for now.
 

Agpp

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bare leds usually have 90-130* beam. reflectors are not the best for leds, tirs are. if you want a thrower get ledil seanna lens

It would be very useful if you provided some more information on why would TIRs be better than reflectors.
Actually....I understand how TIRs can have larger working area at the same diameter and how total internal reflection is the most effective form of reflection. I also understand the relation between the amount of collected light, reflector proportions and emission profile.
Nevertheless I observe that in practical lights, the throwiest-for-diameter ones tend to use either aspherics or reflectors. This is something I don't understand, but would love to.

I would also like to understand how does Seanna work.....I would guess that it focuses the main lens on the front of the pre-collimating TIR, multiplying that TIRs surface luminosity. Which I would guess is not very high. But then it wouldn't work well, so I suppose at least one of those guesses is wrong.

If you can help me with understanding one of those things I would be much obliged.
 

louieatienza

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It would be very useful if you provided some more information on why would TIRs be better than reflectors.
Actually....I understand how TIRs can have larger working area at the same diameter and how total internal reflection is the most effective form of reflection. I also understand the relation between the amount of collected light, reflector proportions and emission profile.
Nevertheless I observe that in practical lights, the throwiest-for-diameter ones tend to use either aspherics or reflectors. This is something I don't understand, but would love to.

I would also like to understand how does Seanna work.....I would guess that it focuses the main lens on the front of the pre-collimating TIR, multiplying that TIRs surface luminosity. Which I would guess is not very high. But then it wouldn't work well, so I suppose at least one of those guesses is wrong.

If you can help me with understanding one of those things I would be much obliged.

I could not find a US supplier that stocks a Ledil Seanna. Because I'm curious, I back-ordered 2 since they're only something like $25 each. They come from Finland. But to me it looks like a lens focusing onto a Fresnel lens. They also claim 94% efficiency and 1* beam dispersion with an Osram Black Flat... I won't know till I get them, but have a nice small project for them when I do.
 

Agpp

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I could not find a US supplier that stocks a Ledil Seanna. Because I'm curious, I back-ordered 2 since they're only something like $25 each. They come from Finland. But to me it looks like a lens focusing onto a Fresnel lens. They also claim 94% efficiency and 1* beam dispersion with an Osram Black Flat... I won't know till I get them, but have a nice small project for them when I do.

According to Ledil, Black Flat driven to 850 lm gives 956 kcd and 800 lm OTF. XHP35 HI driven to 2500 lm gives 1029 kcd and 2080 lm OTF.
 

alpg88

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I could not find a US supplier that stocks a Ledil Seanna. Because I'm curious, I back-ordered 2 since they're only something like $25 each. .

that is strange, they are over $50usd each, and they are available at mouser, they have 9 in stock as of 10am est
 

louieatienza

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that is strange, they are over $50usd each, and they are available at mouser, they have 9 in stock as of 10am est

CDI sells them for half if I'm not mistaken.... Ill check mouser again but at $50 each that's a bit steep.

Just checked to confirm.... I do have 2 on back-order as I'm not exactly in a rush.... 6 weeks is fine for me.
 
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alpg88

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never seen anyone sell them for 25 before, but only looked in mouser and digikey. $25 is a much better deal, i was not aware of cdi store before, thanks for bringing it to my attention.

i wonder if there is a way to know if they are getting anymore in stock, if it worth waiting, cuz price is very attractive
 

louieatienza

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According to the sales rep they have a 6 week lead time.... So not holding my breath, but at $50 there are other options. It's nice however that its an integrated unit.
 

alpg88

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According to the sales rep they have a 6 week lead time.... So not holding my breath, but at $50 there are other options. It's nice however that its an integrated unit.

that seems too vague of answer, so i called them, they are not ordering to keep them in stock, this item is not popular, someone placed an order for 2 pc, but they have no eta on that yet. so unless people order, they will not reorder just to keep in stock, as they do with more popular items. can't blame them thou, i used to work in retail, if items sit on the shelfs too long they get lost, misplaced... etc so no surprises businesses do not stock items that do not move fast.

if you need one, 50 bucks may not be that terrible, but if you need several, might worth ordering from cdi and wait.
 
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