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Old Mar 04, 2013, 05:17 PM
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davidmc36's Avatar
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How would yo reflect an LED

I want to put strobe lights on the wing-tips. Of course the LED does not have a very wide viewing angle. What would you use to reflect/refract the light so it could be seen from more than just straight on?

I was thinking of something like this to attach to the front of the LED:

http://www.ebay.com/itm/8mm-Alexandr...90858835518%26

I also thought of a small reflector made similar to a small flashlight reflector, without a hole in the center, and put the LED out front of it, pointing back at it. I don't know where I would get such a thing.

A tiny version of this would be nice:

http://www.ebay.ca/itm/LOT-GENERAL-E...item43adb74b58
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Old Mar 04, 2013, 05:24 PM
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I wonder what they do with these. Wire in series so they will take 12v or parallel with a resistor?

http://www.ebay.ca/itm/10x-194-168-T...item4164bfb142
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Old Mar 05, 2013, 01:54 AM
Stuart
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Quote:
Originally Posted by davidmc36 View Post
Of course the LED does not have a very wide viewing angle. What would you use to reflect/refract the light so it could be seen from more than just straight on?
Try frosting the surface with a little fine sandpaper.
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Old Mar 05, 2013, 02:29 AM
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I'd just use an LED with a wide angle lens built in. There are plenty of them .

Steve
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Old Mar 05, 2013, 05:02 AM
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Originally Posted by srnet View Post
Try frosting the surface with a little fine sandpaper.
That seems to work well for the red one. I did a couple for the beacon with 400 paper and I think it should look fairly good as the whole thing seems to glow red now. I was thinking painting the tip of it white will also reflect the light back into it and make the diffusion from the sandpaper look even better.

I thought doing that for the strobe might make it lose some of the "sharpness" but may be worth a try.
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Old Mar 05, 2013, 05:09 AM
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Quote:
Originally Posted by slipstick View Post
I'd just use an LED with a wide angle lens built in. There are plenty of them .

Steve
Will have to do some more shopping and see what I can see. I think I saw some browsing around but ended up with the ones I have since they had higher mcd numbers.

Maybe this may be what I am looking for:

http://www.ebay.ca/itm/100pcs-5mm-Wh...item2c6010d079

Or maybe this:

http://www.ebay.ca/itm/New-50pcs-5mm...item5aeeb5f3bf

They say 14,000 but the ones I got are 55,000

I saw some others that have the top with a cone shaped depression which I could reproduce with a drill bit but wouldn't it need to be polished? What if I just did that and painted it white?
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Old Mar 05, 2013, 08:03 AM
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Aaahhhhh.....pi$$ on it, I just ordered a couple of these:

http://www.hobbyking.com/hobbyking/s...dproduct=11744

Will use the LED's for tail nav lights maybe.
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Old Mar 05, 2013, 02:46 PM
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For brightness and viewing angle I think nothing beats these http://www.cree.com/led-components-a...onal/xlamp-xpe . They're very small, surface-mounted, and need a heatsink if they're going to be on continuously. But for strobe-like flashes I've been using them for several months now without a heatsink, without any apparent problem. They're visible in daylight at normal flying height, and with them angled at 45 degrees sideways in the wingtips, I can easily see both of them when the plane is coming towards me.
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Old Mar 05, 2013, 04:26 PM
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Cool thanks. May try buying some of those.
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Old Mar 05, 2013, 06:27 PM
Micro Crazy Man
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I build flashlights using many of the Cree LED types. They are fantastic and bright as mentioned most need a heatsink for continuous use. but having them blinking will work just fine if you look at many of the cree leds there is a bubble over the diode this is used to increase the viewing angle as well as protect the phosphurous. I have had the bubble come off on some leds and was able to replace it with a dab of clear silicone while the light is slightly dimmer the viewing angle was still quite good. Try it out you want to create a small bubble shaped dome over the led
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Old Mar 23, 2013, 09:46 PM
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I picked up some of the CREE LED's and started doing an install and was a little disappointed with the result. Were not as bright as I was expecting. Then got browsing around the specs and got to thinking.

I had just grabbed a resistor from a bag of ones that came with some other diodes to use as a current limiter. Once I did some voltage checking I discovered I was not running any where near the max that they say is allowed. Once I fiddled with some resistance values I am now seeing the kind of bright light that I expected.

Now I will have to take the current limiter off the circuit board that I made with the ATTiny flasher and put the correct resistor at each diode so I get nice bright light. I will shoot for very near max allowed voltage since they will be always just on a flash cycle and I have retained some of the heatsink they came with there will be no fear of overheating.
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Old Mar 24, 2013, 03:56 AM
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I got mine without heatsinks, davidmc36, and sized the resistors so that they would run at 500mA (about 50% to 80% of maximum, depending on colour) at 5v input. Resistor values range from 2.7ohms 1watt (green) to 5.6ohms 2 watt (red). They're running on a strobe cycle which results in them being on for approximately 2% of the time. In that scenario they don't seem to suffer any over-heating (I've been using them since Spring 2012), but I've used fully-rated resistors, rather than the "standard" 1/2 watt ones, just to be safe.

In the model they're installed in at the moment the landing lights are regular 5mm LEDs, but I've got a couple of heatsinks for the Crees so I can use them for landing lights in the next installation. Might have to reduce their brightness so I don't blind myself when landing
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Old Mar 24, 2013, 06:55 AM
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That's about where I figured I would end up once I finish fiddling around is the 3 to 5 ohm range. The last check I did was with 12 ohms putting about 6.3 volts into the Tiny. It puts out about 5.8 volts on the outputs but that was a bench check 5 cell and the battery pack in the plane is only 4 cell so it will only need a smaller value resistor. The Cree's should be super bright once it is all calibrated and with two in each wing tip it will make for a pretty realistic strobe. It will be nice to have the choice of LED's or the Xenon.

I have some 10mm whites for landing lights in the 182 and running them in series off the Rx pack. Now that I am working out the brightness of the Cree's I just may work out a set-up for the Twin Otter using the Cree's that came with heatsinks. I could set up landing lights and keep the area of wing leading edge cut-out to a minimum.
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Old Mar 24, 2013, 08:06 AM
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what cree chip did you get I wanted to mention the R2 its a tiny package and offeres the most light output for the package size. Most of the flashlights I build are made for throw meaning they cast a laser like beam of light rather then flood an area this is largly dependant on the reflector type but you need LED power as well (Lumens). I have run R2's using a good driver from 1.5 - 7.4V the higher the voltage the more that LED will shine. If you look for proper mounting plates (Star) for these they are aluminum and sink heat well for your needs that would be all you need for long life as your not running continous for extended periods.http://m.dealextreme.com/p/cree-xr-e...ium-star-15943. Stars can be bought in different sizes so look for the smallest to save weight
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Old Mar 24, 2013, 08:21 AM
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I got some of these:

http://www.ebay.ca/itm/221192861752?...e=STRK:null:IT

That star looks nice as the cut-out areas will make extra surface area for heat transfer.

Are the ones toward the bottom the R2?:

http://ca.mouser.com/search/refine.a...aign=119142901
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