Unknown IR LED - how can I find the wavelength?

The title almost says it all.

I have an IR LED in a remote control circuit and I may need to add an extra LED.
The existing LED has no special mark, is a simple 5mm clear LED.
How do I find the correct wavelength so I can buy similar LEDs?

LEDs are not pure like lasers are, your IR LED will be producing a relatively broad range of wavelengths.. and your receiver will be looking for a relatively broad range too.

whatever you try, your chances of success are high.

true that. But if you really need to know, borrow an optical spectrum analyzer from a pal

Or get your mits on a webcam without an IR filter (remove it if it has one).. use a CD as a grating, and you have a VERY crude spectrometer.

take a look at this:

http://www.cs.cmu.edu/~zhuxj/astro/h...ctrometer.html

that is pretty impressive!

IR LEDs are either 850 or 950 nm. Industry standard remote control receivers are optimized for 950 nm IR LEDs, you can use them without further checking the presently used LED, I think. Other important parameters are maximum current (usually about 100 mA continuous) and half angle of the radiated beam.