LED question

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Hi,

I am looking to try something crazy. An LED flash bulb for a camera. I have 5 volts to work with and I am looking to make a PCB with an LED or several LED's. A few questions for anyone with experience.

1 - Does adding an additional LED increase the brightness?

2 - Can I 'over drive' an LED since I am only nailing it with power for 1/4 second or so.

If anyone has some tips on trying to get a high intensity light output from an LED, or several with 5 volts @ 1A current supply it would be appreciated.

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1 - That depends on what kind of 5V you have. If you have enough power it will be brighter.

2 - You can overdrive a LED quite a lot. As a general rule can run double the current for half the time. And since the human eye interpolates the light it will look a lot brighter. There are limits thou, a colleague more or less by mistake put 5kV over a LED. That popped the top of it quite violently.

It also all depends, if you are going to sell this thing you are making, I wouldn't go out of spec on the components.

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Found this while looking at Google's results for "LED camera flash":
http://cds.linear.com/docs/Desig...

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There are some LED's designed specifically to met those specs. Check out Ceramos LEDs from Osram as an example. I have one LED on my dirty hands that handles 1W (3.6V@350mA) within 3x3 mm.

Thermal management is important, though.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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You can exceed the power specs if it's just a flash, though, as long as you stay under the surge current limitations. What time span defines a 'flash'? Well, one that doesn't fry your LED. :) (Max current sometimes has a time spec; eg. 250ms.)