FreeTrack Forum

I'm looking at getting these diodes from Radio Shack USA

http://www.radioshack.com/product/index.jsp?productId=2062565&cp

High output infrared LED 5mm 1.2VDC 29mA 940nm

Resistors, three each at 43 ohms.

I'll have to sand the diode to get a wider view.

Will this work, are the values of the diode and resistor correct?

How much tolerance in the resistor value do I have?  Not sure of resistor availability so say would a 25 or 50 ohm resistor work?

Thanks
Curtis
Montana

hello cloudyifr

we have currently a problem with these leds.

look at this topic.

So i wouldn't recommend these leds for now...

btw : these are 940nm leds, webcams have more difficulties to see them than 880nm leds....


Don't you have a local electronics shop near your house ??

if you plan to sand them flat , and perhaps IRmod your webcam, then EVERY ir led is suitable.

So you just have to go in you local shop, ask for IR leds , and be sure to ask for the characteristics (maybe phone them before to know the charac, so you can find out the resistors before going to the shop).



cya

The problem with the IR LED's from Radio Shack is that the website lists the forward current at 29mA, but the package, when you get to the store, lists it at 100mA (with a MAX forward current of 1.2A!)

Basically, I just split the difference and am using a 100-ohm resister on a 3-point ball cap running off of a 9V battery in a clip (also from Radio Shack) that I velcroed to the back of the brim.  I Dremel'd down the tips of the LED so that they're flat & also removed the IR filter from the webcam, and aside from a possible auto-exposure issue with my webcam drivers when using an ND filter over the lens (about which I may post in a new thread at a later date), this configuration has been running fine for about a month now. (I mostly play GPL, but after seeing Kestrel's NR2003 video on youtube, I can't wait for Freetrack v2.2!)

If I had to guess, I'd say that--with the 100-ohm resistor--my LED's are running a little bright, so the 29mA rating is probably more accurate.

I'm not sure I understand what you're saying about the wavelength differences, though, tristan: why do webcams have more difficulty seeing the 940nm?

Also, Radio Shack kinda sucks, but where I'm at, as far as I can find, they're the only game in town.  The small hobby/radio type electronics shops are few and far between, and with Mouser and Digikey wanting to charge like a $5 or $10 handling fee for orders under $25, I just took my chance on a couple of overpriced LED's from RS.  No major problems so far.

--b

Hello basically

If I had to guess, I'd say that--with the 100-ohm resistor--my LED's are running a little bright, so the 29mA rating is probably more accurate.

Not sure.
Once your webcam has been modded, IR leds look REALLY bright (like flashlights!)

You often only need to feed your leds at about 20mA to get it perfectly working.

I'm not sure I understand what you're saying about the wavelength differences, though, tristan: why do webcams have more difficulty seeing the 940nm?

It's all about wavelengths...

IR is not a color, but rather a range of colors. It's just our eyes can't see IR band.

In the IR band, 880nm is close to the edge of the band , near the visible red light, and 940nm is further away inside the IR band.

On an unmodded webcam (with the IR filter still build in), 880nm IR leds are more likely to be seen , because since their wavelength is closer to the visible red light, their light isn't cut off as much as 940nm IR leds by the IR filter (which is made to cutoff IR wavelengths and let through visible colors wavelengths).

On and IR modded wabcam (with IR filter removed), this isn't a problem anymore.


cya.