On Wed, 11 Jul 2007 12:28:16 +1000, "Phil Allison"
wrote:


"Rich Grise"

I've just salvaged some LEDs - here's one:
http://mysite.verizon.net/richgrise/...-green-LED.JPG

and I'm wondering if anybody knows how to tell from the shape of the
leadframe parts, which is the cathode and anode?


** The longer lead is always the anode - impossible to tell that if the
leads have been cut.

Not true. One lead is usually thicker in one dimension where it exits
the device body, if not all the way down the lead.

That is for stamped lead frame designs. Tin or gold wire designs differ,
but the as manufactured lead length indicator is the most common, if, as
you say, they have not been trimmed.

So a test IS required for you to know.

There is another way. The reflector cup is usually always tied to the
same side. Your example may bust that.



(I'm also rather
proud of the photo. ;-) ) Neither of my ohmmeters even makes it conduct;
I'll probably have to set up a little tester, but I thought it was kinda
cool the way the leads hold the chip and so on.


** Mostly, the LED chip sits on the cathode lead - but this is not always
true.

See pic for example of the opposite.




...... Phil