How to find lead of an IR emitter?

[uncoordinated]

I am building my first robot and it requires that i know the lead on the IR emitter so i can connect them to the lead of the LED but I don't have a diode check feature on my multimeter. And the lengths of the "wire" don't vary as a LED would. How do I find the lead of and IR emitter?

 

[Reloadron]

Does the bezel have a small flat on one side? If yes, that is likely (not always) the cathode side. Don't you have a data sheet on the part? How do you know the forward voltage and current?

Ron

 

[dougy83]

If you can see through the LED plastic, you'll notice one of the terminals is bigger than the other - the big one is the cathode (which also corresponds to flat on the side of the LED)

 

[LTX71CM]

If there is no indicator such a flat spot the use a battery with a resistor to test both connection combinations. While trying both combinations look at the emitter through a digital camera, you will be able to see the light.

 

[Jon Chandler]

I can never remember which way around LEDs go, so I included a sketch on my TAP-28 cheat sheet. Look at the 2nd page for a picture showing what to look for.