Author Topic: What IR LEDs?  (Read 11280 times)

Offline prnt

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on: February 19, 2008, 10:07:48 AM
hi,

I'm new to the wiimote project and want to test it myself.

What LEDs are the best for the pens (what angle etc)?

Have someone tried it with a laser?

best regards prnt
« Last Edit: February 20, 2008, 10:56:52 AM by prnt »



Offline inio

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Reply #1 on: February 19, 2008, 11:19:06 PM
Angle: For the whiteboard project, it doesn't really matter, current is a bigger issue.  100mA is good, 150mA is better.

Wavelength: the peak sensitivity of the Wii Remote is somewhere in the 850-950nm range.  The sensor doesn't seem to be that picky.  The sensor bar LEDs appear to be 940nm.

Getting enough diffused light out of a laser would require a dangerously bright laser.  10mW pointed at a diffuse surface won't be visible to the Wii Remote from more than a few feet away - if that even.  If you need something where you can project a point, using an extremely high power IR LED (Osram SFH4230 or SFH4231) and collimating optics in front of it might work, but would be dangerous.



Offline prnt

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Reply #2 on: February 20, 2008, 10:56:23 AM
Thank You!

Quite recently i have ordered some LEDs, resistors and switches. :)




Offline inio

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Reply #4 on: February 20, 2008, 11:43:25 PM
Any of those would work.  For the wii remote the stuff about 850 being better than 950 probably isn't relevant, the mA is the main deciding factor.  If you're only looking at using them as IR pens (where the wii remote would see the light bouncing off of some surface, not the LED directly) than you want narrower angles (20 degrees or less probably).



Offline Iceman1979

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Reply #5 on: February 21, 2008, 07:12:32 AM



Offline inio

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Reply #6 on: February 21, 2008, 10:40:55 AM
what about these bad boys here http://www.roithner-laser.com/LED_HP_single_chip.html

Many of those would work just fine.  To help you figure out the "right one" I'd need to know more about the application though.



Offline inio

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Reply #7 on: February 21, 2008, 11:38:55 PM
UPDATE:

I just did some testing with some Osram SFH4231s (940nm) and SFH4230s (850nm) and ...

With at controlled as conditions as possible:
wavelength      min If @ 30cm      S @ 250mA, 50cm      S @ 1A, 2.7m     
940nm<2mA9810
850nm33mA56

Summary: the Wii Remote is more sensitive to 940nm, but can't focus it close-up (longer wavelengths tend to focus at a greater distance for the same optics, so this makes sense).

S was measured using the full output format as documented at the WiiBrew Wiki