To test how things work if LEDs are placed on the bottom of the PCB, I made a little board with a regular top-facing LED soldered on its edge, with a ribbon cable going to the power source:
http://downloads.qi-hardware.com/people/werner/m1/leds/bot-probe.jpg The PCB has a thickness of 0.4 mm and is held in place with thin double-sided adhesive tape. This means that the whole contraption rises from the PCB a bit more than a real side-facing LED would, but hopefully the results are still close enough. Overview -------- At the bottom of the PCB, we have a lot of flexibility for placing LEDs. In the picture below, I put 0603 component at the center of each connector/peripheral: http://downloads.qi-hardware.com/people/werner/m1/leds/bot-overview.jpg The side-facing LED we're considering has a 0605 footprint and should fit at all the indicated locations. A possible exception may be the IR receiver which is fairly close to the PCB edge. This could be solved by either placing the LED on the side or by moving the IR receiver by perhaps a millimeter inside the board. Video in (11 mm connector) -------------------------- Now to the visual impression. First, I tried video in. Without a cable connected, the LED is very easy to see from the front, and it's clear to which connector it refers: http://downloads.qi-hardware.com/people/werner/m1/leds/bot-vin-empty-front.jpg With a cable plugged in, the LED is partially obscured, but one can still see at least reflections around the connector: http://downloads.qi-hardware.com/people/werner/m1/leds/bot-vin-conn-side.jpg http://downloads.qi-hardware.com/people/werner/m1/leds/bot-vin-conn-top.jpg MIDI (14 mm connector) ---------------------- With MIDI, things are a little worse: while the empty socket looks great and also a view from the side isn't too bad http://downloads.qi-hardware.com/people/werner/m1/leds/bot-midi-empty-top.jpg http://downloads.qi-hardware.com/people/werner/m1/leds/bot-midi-conn-side.jpg the LED is almost invisible when the sight is blocked by the connector: http://downloads.qi-hardware.com/people/werner/m1/leds/bot-midi-conn-top.jpg VGA (33 mm connector) --------------------- With VGA, the problem gets worse. Already without a plug, the connector alone can hide some of the LED: http://downloads.qi-hardware.com/people/werner/m1/leds/bot-vga-empty-side.jpg With a cable connected, it's possible to glimpse some light when looking from the side, but not one photon seems to escape when seen from the top: http://downloads.qi-hardware.com/people/werner/m1/leds/bot-vga-conn-side.jpg http://downloads.qi-hardware.com/people/werner/m1/leds/bot-vga-conn-top.jpg The DVI connector planned for M1r4 is even wider, so this would get worse. Conclusion ---------- While putting the LEDs on the bottom of the PCB works quite well, they can easily get hidden if placed directly under the center of the respective connector. Fortunately, we have quite some flexibility with the placement of LEDs on the bottom of the PCB. If we make sure they're not more than about 3-4 mm from the edge of a plug, visibility should be acceptable: http://downloads.qi-hardware.com/people/werner/m1/leds/placement.pdf - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
