Quote:
Originally Posted by Maxwell777
I'm actually using the sparkfun libraries for the 0603 LED (0603 because I have them on hand). I did the calcs for the LEDs and, if I'm remembering properly, 100 ohm is what I worked out for about 10 mA for a series 3.3v drop across both the LED and resistor. The actual LEDs I'm using are specced at 25mA. I figure if I can go bright I might as well, the more flashing LEDs in a robot makes it look more sciencey. I'll look into dropping the current a bit more though.
Thanks!
I wanted to go the solder bridge route because I figured that it's free, no jumpers to lose, our team only uses one kind of encoder (so we just set the voltage and don't ever need to change it), and anything that sticks up off the board is liable to get smashed and bent when stuck into some drawer somewhere.
I smashed most of the components, the label positioning you see is pretty much the best configuration I could figure out, given vias and stop mask and components.
I did a BOM for all the components on mouser and am looking at somewhere around $2.5 dollars in components per board, the biggest ticket item being the .05" header, at ~$0.8. Via OSHPark, each board is about $2. I figure this seems reasonable, considering the SRX breakout on andymark is $15, what with having to make money and all.
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You should assume 5v for all your calculations, because that's your maximum voltage. You can try getting 10ma on each LED, but there's no point in doing so IMO when 2.2k will work fine and guarantees you don't blind people by accident.
Seriously though, brighter LEDs aren't necessarily better. They'll screw up pictures, get in your eyes, mess up other LED effects on the robot, etc. Indicator LEDs don't need to be bright,
I like the free-ness of solder bridges, but I think some of your concerns aren't too big. 115 made their own SRX breakouts a while back and we haven't ever experienced problems with headers bending, although we've certainly seen everything else. If you want to keep the solder tabs, then putting them all on the bottom and shrinking them will definitely save you space.
The smashing suggestion was mainly if you wanted to focus on making this smaller. I always label my parts as a reference in Digikey, so when they arrive I just match up R1 with R1 and don't worry about values. Obviously it fits fine just as-is.
That BOM sounds about right. Mouser is pretty expensive compared to Digikey, so if you go Digikey you should save a few quarters. The 0.05" pitch header is expensive no matter where you go (it might actually increase in price on Digikey).
You seem to have a good handle on what you want from this design. I recommend OshPark for manufacturing for a variety of reasons like the .brd native uploads, free priority mail, and relatively low cost and high quality.