FreeTrack Forum

Hello everyone, I would like to get some help on how to construct a 3 point model. I'm planning on using a wiimote and I have found the IR LEDs here

http://www.seeedstudio.com/depot/5mm-ir-led-940nm-p-70.html

Can someone please confirm that the forward voltage is 1.2 V? I'm not too sure how to read the table on that website and I can't tell if the forward current is 12 or 20 mA. I would really appreciate it if someone could clarify this for me.
Next, I plan on using 4 AA NiMH batteries which are labelled with 1.2 V so my voltage value is 4.8 V, correct?
According to the "LED Assembly Wizard" I either need a 100 or 62 ohm resistor with this setup assuming the current is either 12 or 20 mA. Now which one is it??

Thank you,

Yes, looks like the forward voltage is 1.2V.

Not totally sure about the current, but I'd go with 12mA.  Sounds a bit on the low side to me though, but there are people on this board far more experienced than I who will hopefully chime in and tell you for sure.

Your 4 AA batteries will be 4.8V or 1.2V depending if they're connected in series or parallel, respectively.

For example, these are connected in series (note the voltages):


And these are connected in parallel:


Also, with those LEDs you may want to sand them down a bit so that the infrared light they emit forms a wider beam than they do currently.  I used a disposable nail file, but sandpaper, a concrete surface, etc works well too.  If you sand it down to about 2mm above the inside emitter components, you'll get a nice wide beam that your wiimote will more easily be able to track as you turn your head.

Hope that helps, and good luck!

Thank you for the response Karin. I have taken a few physics classes in the past and know a few basics like connecting cells in series or parallel. I'll keep the sanding in mind.

I hope someone can clear up the forward current though.