Those Danged LEDs Again

I was caught by one of my own favorite “simple” traps last week: the dreaded LED footprint mess.

I designed a board based on the Microchip PIC32 — it’s a ChipKIT Arduino-compatible board — that has a number of RGB LEDs on it. I used RGB LED part number LTST-C19HE1WT, from Lite-On. The datasheet is easy to find, and the footprint information is right up front, just the way we like it.


11 designers nb figure 1Almost all is well, but I somehow missed taking my own advice and I didn’t double-check the footprint.The footprint I used is more or less 180 degrees off from this one. The common anode is still on pin 4, but the numbering is different. It’s got pin one in the same place, then pin two is in the lower left. Pin 3 is on the same place, and pin 4 is on the upper right. That’s the conventional pin numbering order.

Fortunately, the fix won’t require any mod wires. If I rotate the LEDs 180 degrees, the anode will be in the right spot. All I’ll need to do is adjust my software for the correct R, G and B pin locations.

Duane Benson
I’m dizzy with rotation

http://blog.screamingcircuits.com/