I think both pictures are correct.

Unfortunately, most LEDs have the Anode lead longer than the Cathode lead.
The pin-1 mark is usually an indicator for the longer (Anode) lead.  The dot
or bar on "regular" diodes is always on the Cathode end.  This is the
confusion!

Often, round LEDs will have a flat spot on the Cathode end (indicating the
bar on the diode symbol).  Sometimes the flat is parallel to the two pins,
which is useless for the Anode/Cathode question, but let's hope the
silkscreen matches the flat spot.

So far, I've been able to spot the cathode by looking at the internal
structure.  On all diodes I've used, the die mounts in a recessed Cup which
is the Cathode (C-Cup-Cathode) connection.




Carl Van Wormer
Cipher Systems
1815 NW 169th Place, Suite 5010
Beaverton, OR  97006
Phone (503)-617-7447    Fax (503)-617-6550



-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Tuesday, October 26, 2004 7:15 AM
To: [log in to unmask]
Subject: [TN] Diode Pin Numbering Question...


Mornin' All!

There's been a pretty interesting thread going on in the Designers Council
about what is supposed to called pin 1 of a diode...the Anode or the
Cathode. Believe it or not, there's been conflicting answers. So I'd like to
do a little test.

Look at:

http://www.stevezeva.homestead.com/files/LEDPin1.jpg

and tell me if we installed this LED correctly.

Then look at:

http://www.stevezeva.homestead.com/files/LEDPolarity.jpg

and tell me if this this illustration guide I made for our operators is
correct.

(This ought to be good)

-Steve Gregory-

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