Hi Adam, answering on the list, so that you don't have to search the backlog:
cladamw_ wrote: > http://downloads.qi-hardware.com/hardware/milkymist_one/pcb/r4/051412/MILKYMISTONE.pdf > this one is only J27 mounting hole hasn't been moved south 1.5 mm a bit. Hmm, alright. But then I may have another issue: the trace "north" of J27 seems to be a bit too close to the hole: http://downloads.qi-hardware.com/people/werner/m1/tmp/j27.png I calculated the distances (in mm) based on pixel distances in the PDF, using the 100 mil spacing of J21 as a reference. If we use the same kind of spacers as in M1rc3, they may be a bit off-center and exceed the copper area of the mounting hole. Here's an example from an M1rc3: http://downloads.qi-hardware.com/people/werner/m1/tmp/mnthole-screw-offset.jpg If the mounting post ends up over a trace, it could shear (break) the trace, which wouldn't be fun to repair. The hexagonal spacers have rounded corners, so they leave a bit of room, but the screw goes almost all the way to the edge and has the same diameter as the outer diameter of the spacer. I don't know the exact distance, but a keep-out area of about 1.5 mm around the ring of the mounting hole (or an increase of the ring size) may be sufficient. A more precise calculation would go like this: Screw head diameter 5.5 + head diameter tolerance 0.1 - chamfer at screw edge 0.1 + hole diameter 3.7 + hole enlargement due to wear 0 + drill position tolerance 0.1 + drill diameter tolerance 0 - thread diameter 2.9 + thread diameter tolerance 0.1 + layer registration tolerance 0.1 + copper width tolerance 0 --- Min. ring/keep0out diameter 6.6 === All distances are in mm. The numbers are measured on M1rc3, from the rc3 Gerbers, or simply guesses. Here is a drawing with the main parameters: http://downloads.qi-hardware.com/people/werner/m1/tmp/mount-dim.png This shows a likely configuration of J27 in M1r4, assuming we use the same mechanical kit as in M1rc3. The copper ring is only 5.2 mm, so if we use the same dimensions in M1r4, the screw may touch other things. And that trace looks close enough to be in danger. > 1) U26, C178, C256 ~ C260 go to bottom, > 2) C286 goes to east of DMX TX, Excellent ! > 3) TP32, TP38 - TP41 go to top, Nice. Please don't forget to update the schematics, which say "Placement (TP32, TP38-TP41) at the bottom of PCB." If we don't really care where they go anyway, then perhaps we should not mention their location in the schematics. > and else small fix in design files I didn't hunt for them. I hope they're alright ;-) - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
