I attempted to put together an order, today, for the parts needed to populate the Willow Garage Turtlebot power and sensor board. They have a link to digi-key that’s supposed to have all of the necessary part numbers, but that plain didn’t work for me. Also, they were missing some information for several of the parts (such as physical dimensions on surface mount capacitors and a resistor). So, where there was wiggle room, I just ordered a couple of parts, in the hopes that one fits!
One interesting thing (to me, anyway) was that there was a resistor with a value of “0R”. I’m guessing that is a 0 Ohm resistor, a beast that I have not yet come across. But, sure enough, they do exist. Apparently there are at least a couple uses for such thing. One use is to simply jumper over a trace. Another use is a placeholder when there are multiple configuration options available, and you only want to do one board run. From the documentation provided for the Turtlebot, it doesn’t appear to be the former. The datasheet for the gyroscope suggests that you could use a resistor here:
"A single external resistor between SUMJ and RATEOUT can be used to lower the scale factor"
So, I guess the resistor could be a placeholder in case you wanted to adjust the scale factor. Maybe it’s an oversight that they left it in the final layout. Who knows?
For those interested, here is a link to the BOM from digi-key that I put together. The grand total was a whopping $11.24. Note that there is still a heatsink required (which I ordered separately from Newark.com, only because I forgot to look on digi-key first). Also, you need the gyro breakout board from Sparkfun.
I’ll post an updated status when the PCB actually arrives. The lead time from BatchPCB is 3-4 weeks, though, so don’t hold your breath.