RE: [CAD_CAM_EDM_DRO] quickie LED lesson

You can't go by the length of the legs. Whether the anode or the cathode is
longer is an option when you order an LED, that is when a company orders
100,000's from an LED manufacturer, they can specify what they want.
Hobbyist are generally stuck with what they got. I've been told the one
long leg feature is a relic of wide spread hand assembly. It makes it
easier to install the LED's by hand. Depending on how the board would be
oriented, compared to the assembler, would make it easier to have the anode
longer than the cathode, or vice versa. Anyhow, if a round LED has a flat
molded on one side, it is most likely the cathode (Negative). As with
everything under the sun, I have seen exceptions to the rule, where a flat
was on the anode side of an LED. If you have a DMM with a diode checking
feature, you can usually use that to tell for sure. The meter will light
the led just enough to tell you when it is connected right.

Mike

P.S. - Do you need help with a dropping resistor?

-----Original Message-----
From: andrewyslee [mailto:andrewlee@...]
Sent: Saturday, August 17, 2002 1:30 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] quickie LED lesson


Hi,

I am trying to wire up a logic probe. I am not too familiar with the
polarity. Which one is positive, the longer or the shorter leg?

thanks

andre


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