[hpsdr] LED polarity (was: OZY Startup Info)

[Scott Cowling]

Hi Phil & Lyle,

We ran into the same problem on boards that we design here at work.  Even 
LEDs from the same manufacturer and from the same series have different 
pins (A or K) marked. If you have a good microscope (or very good eyes) you 
can see that the die is mounted opposite in the two versions.

We have standardized on marking LED anodes with a "+" sign. It is easy to 
read and does not imply any correspondence with the marked end.

This does not work for Zener diodes, however. :-) On those, we mark the 
cathode with a "K".

This method has really cut down on the incidence of "dead LED" syndrome on 
our prototypes. When we just used a dot or thick bar, we had about a 50% 
chance of getting the parts put on properly. :-)

73,
Scotty WA2DFI




At 08:49 2006-07-17, Lyle Johnson wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
> > To summarize:
> >
> > The CK170 part has the ANODE marked.
> >
> > The CK171 part has the CATHODE marked.
> >
> > Don't ask me why LITEON cannot be consistent in their marking...or why
> > other manufacturers cannot use some standard...  I always do what Phil
> > H did - use a DMM to check polarity before soldering to be sure.
>
>Speaking of consistency, we need to be consistent in how we mark LED
>polarity on the silkscreen.  If we are going to standardize on 0805 LEDs
>and an "a" at the anode, so be it.  I normally associate special marking
>at the cathode end, with a thick bar, for example.
>
>I bring this up only because I am adding LEDs to Janus. Sasquatch will
>probably have a few as well, just because...
>
>73,
>
>Lyle KK7P
>
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