Bright LED Strobe

Hi,
I'm interested in making a bright (>400 candle) strobe with red or white LEDs. It would need to flash at around 1Hz. and have an approx. 60 degree coverage. Clearly this require an array of LEDs. Is this is a practical project, and can anyone offer advice on choice of LEDs and driver circuit design? Or is a xenon strobe a lot less trouble?

Thanks!

hi slk23, welcome to cpf!

greater than 400 candlepower would be quite a feat for a led array of even large sizes. also, white leds, if you chose to use them, have a yellow phospher coating to produce the white light, after the led has stopped getting power, the phospher will still glow for a short period of time, maybe 1/8 of a secong, causing a problem with the strobing effect. reds don't have that problem, but still you have to worry about light output, and the only way you *might* be able to get that is with an array of luxeon star leds, and they cost $8-16 each, depending on where you get them. a xenon would be both cheaper and easier. i don't know much about circuit stuff, but someone else will come along and help you out with that. might i inquire what the application is?

Thanks for the reply Rothrandir. I think you're right, a xenon strobe is more practicable. The application is a small aircraft anti-collision strobe. Most of the commercial units (such as from Whelen) are expensive with bulky power supplies. I was hoping to make something more elegant. I might try adapting a strobe such as:

http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=40000008000&productId=883&parent_category_rn=4500587
or
http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=40000008000&productId=5457565&parent_category_rn=4501499

you could try attaching flashlights to the propellers, that would make you pretty visible something with amazing throw like ultrastingers, it would look like a big white circle from the front!

The LEDs would be lots more efficient than the strobe, which would mean that for the same beam candle power seconds you would have less power going in, and a smaller power supply.

Over a 60 degree coverage cone, you pretty much require 1 lumen per candlepower. So an array of 10 40 lumen Luxeon LEDs (the red/orange ones exceed this) with suitable optics would provide the necessary light output, continuously...and since you need a strobe, you could overdrive them for part of the time and have them off for the rest of the time.

Perhaps a better choice would be the Lumileds Superflux devices. These are 7mm square LEDs, intended for use in things like brake lights on cars (I used them on my bike). They are available with an optic that has a narrow vertical light distribution, but a broad horizontal light distribution, so that not too much light is wasted in directions where it won't be needed. With these optics, you could expect to get something like 10 - 15 candlepower per LED, and the LEDs are only about $0.50 each.

For a drive circuit, I would suggest a current regulating switching power supply. I have a design ( http://www.borealis.com/~winnie/LED_BOOST/index.html ), however it is not suitable for an aircraft electrical system. Feel free to use it as a starting point. Given that an aircraft electrical system might be 12V or 24V nominal, and could spike to higher voltages, I would suggest a design that can tolerate at least 40V on the input, protected with fuses and transient voltage suppression, and capable of producing higher or lower voltage on the output. I would also suggest that the circuit be divided up into at least two sub circuits, each supplying a subset of the LEDs.

-Jon