On the bottom of the led look for a bar and a square.? The square
is pointing to the cathode.? On the top of the LED, there may or
may not be a green marking under the transparent plastic covering
the chip.? That should indicate the cathode.
On the physical picture (parts layer) look for the picture of the
LED to to have (if you're lucky) the same bar and dot, or perhaps
a triangle of 3 dots with the center dot pointing to the cathode.?
That varies by PCB program, though.
Do not depend on the body of the chip to be the cathode and the
wire to be the anode.? That can vary.
If needed, you can modify one of the little LED testers with a
pair of banana jacks, which would connect to one of the measuring
tweezers (just the wires, no electronics).? That would allow you
to select various currents (5 ma is fine), as well as test other
LEDS.
If you're lucky, there might be one that is adapted to surface
mount parts.
The common LCR tweezer style testers may not have enough voltage
for blue and white LEDS.
Harvey
On 5/24/2019 4:00 PM, Lee Studley
wrote:
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K is usually cathode(?Greek kathodos(
"descent"?) )
I think the dot in the "led_sch_top.jpg"" and the green squares
"LED Bottom View.jpg" pictures are on the cathode side.
But the picture Led Top View.jpg is ambiguous
