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Author Topic: Super bright LED array?  (Read 1322 times)
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Manchester, New Hampshire
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For my next Arduino project, I will be making a prop which should emit a bright light when activated.  Ideally it would be bright enough that in a dimly lit room, one would almost need to squint to look directly at it.

Here are my parameters:
* White light
* Less than $50
* No more than 2" wide, but can be longer than that
* Can run off a small battery pack  (Six C cells maybe?)
* Ideally comes prewired and on a board ready to be plugged into my kit

I suppose I don't have to go with leds.  Maybe there's a kyrpton bulb or something I could run off a battery pack which would provide the neccessary light and be a cheap solution.  I'd need a source for the lenses and sockets for them though and some means to mount it.  An LED solution would be preferred though.

I've tried Digikey and Mouser, but I'm not having much luck.  I don't know how many lumens I need for something like this, and there don't seem to be a lot of options for large arrays of leds.

So anyone used these sorts of arrays and have any suggestions?  Or any idea what I should be looking for as far as how many lumens this thing ought to put out?  
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You could probably do this with just a few standard ultrabright LEDs withough resorting to the high power route

Something like this will kick out 30 candelas for a few 10's of mA

http://www.rapidonline.com/sku/Electronic-Components/Optoelectronics/5mm-LEDs/5mm-Ultra-high-brightness-15-deg-LEDs/73421/55-2484

Of course you may end up with a directional light source. You don't say how long you need it to last, but you could probably drive a few of these for a day on 3 AAs

If your eyes are accustomed to a dim room these would definitely make you squint
« Last Edit: November 26, 2010, 11:28:58 am by MarvinMartian » Logged

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That LED has a beam of only 15 degrees.  That's too narrow for my needs.  These leds will sit at the bottom of a box which is 2" wide and 2" tall.  That means I'm looking for a beam which is around 120 degrees wide.  It could be less than that... say, 90 degrees... but 15 degrees is way too focused.

Also, 30 candelas according to this site is equal to only around 1.6 lumens:
http://led.linear1.org/how-do-i-convert-between-candelas-and-lumens/

And I think what I need is more in the range of 1000 lumens, which is roughly the output of a 100 watt bulb.  I can probably get by with half that, and I may determine I'll need to be satisfied with much less, but regardless, to get anywhere close I'd need a ton of leds at only 1.6 lumens each.

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Don't underestimate the utility of an incandescent light bulb when you need a omni-directional light source.  A 5 to 20W halogen bulb would probably meet your needs, as would one of the 5-10W high-power LED arrays like those here:
http://www.dealextreme.com/products.dx/category.917

Depending on budget, you might be best starting off by experimenting with some of the high power LED flashlights of the "consumer" variety.   Or maybe not.  You said "prop" ?  So you want it to look bright compared to STAGE lighting?  My 3W 2D Maglite is pretty bright, and the LED is pretty broad-beamed without the reflector and optics, but the beam gets pretty washed out even in bright room lighting...
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I considered a halogen bulb, but there's several problems with that; one being that it could be a potential fire hazard since it may get hot.

As for the prop...  It's a costume prop, not a stage prop.  

Here's what I'm making the circuit for:
[media]http://www.youtube.com/watch?v=NRt0SG-hepU[/media]

Obviously I can't recreate the sparks jumping off the trap and flying about in the beam that it emits.  But a simple bright light that turns on when the doors open ain't gonna look that cool in person.  So I'm thinking maybe I'll do one bright light in the center which pulses in brightness, and surround it with a ring of other leds which animate in some sort of chase pattern.  And of course the bargraph will animate and the red light will blink when the doors close, and the cycle is complete.

But anyway, that's what I'm working on.  And I'd like to make it as bright as is reasonable so as to have it be sufficiently impressive. :-)
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http://www.sparkfun.com/products/563

These things are painfully bright.

Lefty
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Retro:

Thanks for that!

I took a look at those Luxeon leds.  

The datasheet says they put out only 65 lumens (as opposed to the 1000 lumens I believe a 100 watt bulb puts out) yet people say they're super bright and leave afterimages on their eyes when they look at them.  Now, I would assume this was because the beam is narrow, but the datasheet says the beam is like 140 degrees.  I don't know what to make of that.

Also, from that site I then went to Digikey to see if their prices were better, but I couldn't find the LEDs there.  I did however find the aluminum PCBs to mount them to cheaper.

But then I found the Luxeon website, and it appears they actually sell direct.  And I can get the leds premounted on the aluminum PCBs, and I can get lenses for them too.  Plus they even sell dimmable constant current drivers for the LEDs.  And there's a wide array of color temperatures available and colors other than white as well.  I think I've found my source!

But there's one thing that bugs me.  The lumens.  

The LEDs you linked to, the Luxeon IIIs...  Those are at the end of their life.  They're not being made anymore.  Those are the ones that are 65 lumens.  And people said they were super bright.

But the new Luxeons... the Luxeon Rebels... They're 2-3x as bright, according to the Luxeon website.  Is that going to be too bright?

Also, another little wrench was thrown into the works when I noticed while Luxeon sells direct, they don't seem to have a whole lot of stock on hand.  I don't want to have to wait 3 to 5 weeks every time I need an LED.  So I searched Octopart to see who else might carry them and have them in stock, and the only place I found was FutureElectronics:

http://www.futureelectronics.com/en/Search.aspx?dsNav=Ntk:PlainTextSearch|3417276|3|,Ny:True,Nea:True

Oddly, even though they carry the Rebels, they're quite a bit cheaper than the Luxeon site, and the lumens listed are more in the range of those Luxeon III's on Sparkfun's site.  I dunno what's going on there.

Other than that, the only concern I have with these is I'm not sure  how I'd work them in with my idea for animating several in a chase pattern.  I can't fit a ring of these in the trap because said ring, if made up of the starboard heat sinks, would end up being too wide.  And if I mixed and matched these with dimmer leds they'd probably outshine the other leds by an order of magnitude and you wouldn't be able to see the animation.  

But I like the simplicity.  It's almost a plug and play solution.  Perhaps a single pulsing light would be sufficient.  I could animate the bargraph at the same time to add some interest.  Hm.

[edit]

Just noticed they have leds mounted on 10mm squares too.  That gives me some more options.  Though at almost $10 each, I don't think I'll be sticking seven of these things in a single trap.
« Last Edit: November 28, 2010, 09:07:55 am by scswift » Logged

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The Luxeons are perfect for what you are doing.  I've been playing with a 1W Luxeon Star (about 60lm), it's BLINDING at close range- looking at it directly is painful.. and that's just a one-watter.  From many sources, these can be had for $2-3 plus shipping.  Though it really should have a constant-current driver, I've found that I can get away with a limiting resistor and switch it with a TIP120, but have used 2n3904 and 2n2222 also.  It wants around 3.4v, so it draws a bit under 300ma, which is within spec on low-end transistors.

That being said, discrete LED's in an array can be made to whatever you want, and here's where you go to have the array design math done for you:

http://led.linear1.org/led.wiz

Sounds like the site might have some good info for you, the free calculators there are a huge help over and over...
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I found some videos on Youtube which give an indication of how bright the LEDs are.  Here's a 3W Luxeon:

[media]http://www.youtube.com/watch?v=u1RvcsZD0YY[/media]


And here's a lightsaber I found which uses Luxeon Rebels as well:

[media]http://www.youtube.com/watch?v=X0gTMmLmw0k[/media]


Not sure what the wattage is, but around 1:40 he turns on the white light and it looks pretty bright.
« Last Edit: November 28, 2010, 07:19:33 pm by scswift » Logged

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