Is The LED Footprint Pin Orientation Backwards?

I’ve spent way too much time chasing this one down. I could modify my symbols or footprints, but I’d rather understand the default Kicad configuration. I’m a very-low-level intermediate, I guess.

Assuming the square pad of the LED is positive / anode / long leg, this circuit is a dud.

  1. Is this assumption wrong?
  2. Is there something else I’m doing wrong?

I’ve read in multiple forum threads that this shouldn’t be occurring so renamed my library and modules folder in KiCad/share/kicad to libraryX and modulesX and redownloaded the latest version from https://kicad.org/libraries/download/

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The KiCad library is correct. See e.g. www. denatechnologies. com/ipc-standards/. (Edit: dead link)

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The flat side of the LED is always the cathode (short leg, ground). So in this case the square is the ground pin. I guess your assumption is wrong. :slight_smile:

Diodes are conceptually the exception to the rule of pin 1 being the positive for polarized discrete components. The industry standard is to make the cathode pin 1 for diodes.

Easy trap for beginners.

As a future warning, watch out for transistors. There is no industry standard for the 1-2-3 pinout mapping to emitter, base, cathode. You can lay out your schematic with any transistor symbol, but once you decide on a specific device you need to read the datasheet to figure out the pin mappings and change your symbol (and associated footprint) appropriately before sending to pcbnew.

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This bit me on board I had fabbed. SOT-23 and Dpak are typically different. If the package is changed for current capability then the schematic symbol pin-out will very likely need to be changed.

The KiCad library is correct. See e.g. http://www.denatechnologies.com/ipc-standards/ 3.

Thanks! This explains everything. I had picked up somewhere along the line that a square pad was positive. I certainly liked life better when I believed that. I’m perplexed by this standard, but what else is new?

Thanks everyone!

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