i had sort of the same problem. i could make the pens show up really well pointing at them but sideways there were not so great. On my pens i started putting something semitransparent on the end to stop the direct beam of IR light and diffuse it a little more. that helped a ton.

i still have not gotten something for my big mama jama black pen but my other two do very well with an end cap on them

Thanks for the feedback on this. The strength of the led is definately the problem. I guess I need to order some online.

nah, no resistor yet. I can see it with my camera on my cell phone its just really dark. I think SSpeare  is on to something with the 16mw comment. I think changing the led will make the difference

Ok, so my TSAL6200 leds came in today and I wired one up to an led pen from walmart. Using my moded web cam I took a pic of the two sources pointing on the ground. I can't tell if its brighter or if its the differance in angles of the leds. The TSAL6200 is 17deg and 40mw the radio shack is 45deg and 16mw.

Here is a pic of it from the view of the webcam.

Thanks for posting that. I was not aware of google not allowing hotlinking of images.

Thanks
John

Thats what I thought too.

940nm is about twice the intensity as 850nm when viewed by the Wii Remote.

For a given wavelength (= given chemistry), max current is pretty much proportional to radiated power.  Running much above max current will kill the LED, so you have to be careful.  To do things right, use a higher source voltage and current limiting (don't connect it directly to a battery).  For example, for a 2.4V source (2x rechargeable AA batteries), and 1.2V (typical) 100mA (max) LED, the resistor should be at least R=V/I=(2.4V-1.2V)/100mA=1.2V/0.1A=12ohms.  If you want to get really fancy, measure the current (you can do this using a ammeter or by just measuring the voltage across the resistor and using I=V/R) and adjust the resistor until you're near your LED's rated maximum.

Power (wattage) isn't really that useful of a metric to compare unless the LEDs have the same current, angle, definition of power, and about the same wavelength.

For the Whiteboard project, you only care about angle if you want to be able to hold the markers more than about 1cm away from the board and not lose range.  If you do want that, you want the narrowest angle possible.

For marker's, the field is just too wide.

For non-marker applications, I like the following LEDs:

Panasonic LN52 & LN152 950nm, 100mA, approximately flat falloff over slightly less than a hemisphere, or a full hemisphere.  Not good for long range applications, but over short ranges (<4 feet) they work great.

Osram SFH 4231 940nM, 1A, approximately lambertian angular falloff.  Expensive though.  If you want to project IR points onto a screen, these plus some optics are you best bet.  The SFH4230 works in a pinch, but you'll get about half the intensity at the sensor for the same current. Powering these near their current rating is tricky - they need to be mounted to a heatsink to actually run at 1A, and merely supplying 1A to them could prove tricky as using a resistor for current limiting becomes problematic (if you don't understand why, don't try it).