Wednesday, February 9, 2022

Verification saves my bacon - conflicting numbering for ATX-24 power supply socket

 When I checked into the arrangement of the pins on the ATX 24 socket to ensure that they matched the actual arrangement of voltages and control signals from an ATX power supply, I discovered that everything was scrambled on my board.

The ATX-24 schematic symbol was included in the KiCAD distribution but not the footprint for the connector. I found that part on SnapEDA and downloaded the file. Sadly, the TE layout from SnapEDA did not use the same numbering schema as the rest of the world.

The socket should have pins numbered, across the top, 1 to 12 from left to right, then drop to the bottom and from left to right they are numbered 13 to 24. The layout I downloaded has them assigned 1 top left, 2 bottom left, thus zig-zagging with 23 and 24 in the vertical column on the right side. That would have produced a disaster had I plugged in a supply. Worse, the board would have been scrap. 

I have done all the improvements on legends, verified the screw terminal dimensions give adequate clearance, and checked the ATX power supply connector. The file is looking pretty good right now, but I still have three critical checks to apply. 

  1. Verify the mechanical spacing of the header pins will fit the Ztek FPGA board. 
  2. Verify the connector pin assignments agree between Ztek board and my PCB.
  3. Check that each and every signal goes to the intended destinations.


No comments:

Post a Comment