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Unread 03-27-2012, 05:26 PM
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Target illumination LEDs - What color? How bright?

For those using LEDs with the Axis camera to illuminate the target, what color works best and how bright do they have to be? A quick perusal of Ebay shows a wide range of colors with brightnesses from 5000mcd to 20000mcd. Do some colors work better than others? Would twenty 5000mcd LEDs work as well as ten 10000mcd LEDs? Do we even need the LEDs? I have seen some teams using the Axis camera without them.

For those that are using LEDs, did you buy a pre-made widget with the LEDs already on it or build your own from individual LEDs? How many LEDs or what total brightness should we be looking for?

Just looking for some data, anecdotal or measured.

Thanks
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Unread 03-29-2012, 08:25 PM
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Re: Target illumination LEDs - What color? How bright?

We bought pre-made LED rings. Red and Blue were out, too much potential for on-field confusion with alliance colors. Yellow wasn't very bright, so green became the color. White were more expensive.

They really do not have to be that bright, the retro-reflective tape is pretty good. One AA Mag-lite might work OK, for example.
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Unread 03-30-2012, 07:23 AM
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Re: Target illumination LEDs - What color? How bright?

This year we also purchased the premade rings (and cover) and had no problems (we even used blue). At our week 2 event green, purple, and other "odd" colors seemed popular.

This was after an exercise in students trying to make their own array and it not turning out so well.
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Unread 03-31-2012, 11:27 PM
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Re: Target illumination LEDs - What color? How bright?

I have seen at least one team using what appeared to be a diffuser on their ring-light. Wouldn't this diminish the retroreflective effect and/or interfere with your alliance partners aiming?
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Unread 04-01-2012, 12:29 AM
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Re: Target illumination LEDs - What color? How bright?

You want the light to be emitted in a wide pattern rather than directionally. That way the targets will still be reflecting when they're not directly in front of the robot.
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Unread 04-01-2012, 06:51 AM
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Re: Target illumination LEDs - What color? How bright?

Quote:
Originally Posted by PAR_WIG1350 View Post
I have seen at least one team using what appeared to be a diffuser on their ring-light. Wouldn't this diminish the retroreflective effect and/or interfere with your alliance partners aiming?
LEDs tend to be very directional. Adding a diffuser will widen the area of illumination, but will weaken the amount of returned light.

Fortunately you dont need much returned light and you can block out all but the exact wavelength you are looking for, meaning that you will need to do some teating but as long as the returned light is detectable, the amount of returned light does not need to be a lot.
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Unread 04-03-2012, 04:11 PM
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Re: Target illumination LEDs - What color? How bright?

I built a demo illuminator that used 3 Cree xrc green less running at 300 ma . If they were more than 10 cm outside the range of the camera the reflection fell dramatically. When using the ledil optics I could not get a wide enough beam angle. It was flooding the camera.

We have 9 xrc less now on tristars that can illuminate across the entire field, but the team is using the largest angel eye instead.
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Unread 04-07-2012, 08:47 PM
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Re: Target illumination LEDs - What color? How bright?

We used some green leds this year to use for our auto-aim system which even though the auto-aim failed we kept them on cause they looked cool.
First year that we ever used these and for the time that we needed them they worked beautifully so ill try to have the team give em another shot next year

Last edited by JP Carlin : 04-07-2012 at 08:49 PM.
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