Hi,

I need to buy IR LEDs in order to build a 3-point clip.
I do not know what the recommended specifications of the IR LEDs are. Note that I cannot purchase Osram SFH485P LEDs, so disregard those.

NM: Does it matter if the IR LEDs are 850, 880, or 940 or a similar number of NM?

Viewing angle: Most of the IR LEDs I found on eBay are 15°, and 25°-30°. The recommended SFH485P are 40°, but I read that flattening the LEDs helps increase the viewing angle of the narrow ones.

Current and voltage: do these matter, or do they merely affect the type of batteries and resistors I will need to power the LEDs with?

Other: Anything else I forgot, please mention it.

Hi Yonyz,

I noticed that you posted this question on the Freetrack Forums also; that is the best place for LED building questions, but I will try to help.

I have built half a dozen freetrack systems for friends, I use a cheap 5mm IR-LED from Radio Shack (I realize that you probably do not have access to that store but the point is; pretty much any electonics supply store will have the cheap IR-LEDs that I used). Here is a link the the exact type:
http://www.radioshack.com/product/index.jsp?productId=2062565

They are indeed the 940nm (which means they are higher on the light spectrum and should be completely invisable, the lower the number the more red the light emmitted will be. I think 800+ is invisible but I am not sure) and have a forward voltage of 1.28v with 100ma rating.

Here is a tutorial on the Freetrack forums on sanding down a standard IR-LED to get the wide angle output that you want. I grind mine down on a piece of sandpaper and the polish it back up using wet polishing paper (650 grit is all I go to).
http://forum.free-track.net/index.php?showtopic=2667

I use a USB plug to supply power (5v) to my headsets which requires a resistor to limit the current, you can also pick up an R/C battery pack (rechargable) at a hobby store and use that (4.8v) or make your own from AA batteries.

Here is a good youtube video that shows the total process including camera alteration and 3-point cap construction.
http://www.youtube.com/watch?v=5QqAqb_SZV0

and the circuit diagram that I use:

The wavelength (nanometers) does matter. What are you going to be using for a camera? (modified web cam, Wiimote, or ???). Ideally, you want your IR LED's wavelength to match up with the camera's capability.

PropNut, thank you for all the information. Isn't $2 for a "simple" LED way too much?
I have seen packs of 50 for $6 on eBay.

CyBerkut, I will be using a PS3 Eye.

I found where to buy SFH485P IR LEDs. Now I need to know exactly what type of resistors to buy.
The "Easy SFH485P Setup" post on the FreeTrack forum says 3x30Ohm, 1/4 Watt. What do you think of these?

Hi Yonyz,

True, 2.00 each is expensive if you are building hundreds of units. I was originally going to build only one so 6.00 for LEDs that I could get without waiting was not bad. And the other headsets were not planned, rather they too were built as friends wanted them and 6.00 was not an issue for them either. I had not found large (5mm) IR-LEDs that match them on Ebay other than from China and I did not at that time want to wait for shipping to arrive. I should have looked at larger supply houses here in the US (such as Jameco.com) but I did not see a need to have a box of LEDs laying around. I could probably have used smaller LEDs but I like that larger size when sanding them down. To each his own I guess.

The " Easy SFH485P Setup" thread is refering to three separate 30ohm resistors so the one that you linked to should be fine. That circuit is a parrellel circuit (hense three separate resistors) and mine is a series circuit (where I only need one resistor).

Edit: Woops, misread your last post so I fixed my last paragraph to reflect the correct information that you were looking for.

What is a series circuit?
Also, my main problem not is figuring out how to actually build a clip. Really, I have absolutely no idea where to start, and most of the information in that thread is about the circuits and not the clip itself.