Hi, everything is going great with the $50 robot so far. Thanks so much for everybody's help so far (and the admin for setting up the tutorial in the first place!). It's really been great.
I have yet more questions - electricity is still quite unintuitive to me still; hope these questions aren't getting old fast:
1) If I send a high signal from a microcontroller output is it always the same voltage as the input VCC? i.e. if I send 5V to the microcontroller and send a high signal out (say, to control the LED), is it also 5V?
2) What kind of current can go through a microcontroller? Apparently it is safe to power the LED from current passing through the microcontroller, but I assume it probably would be a bad idea to wire one of the outputs, say, PD0 to my servo power wire and expect it to run, correct? Is there a ballpark figure for what's safe and not?
3) I just wanted to try some electrical math for practice before I plug it in for real. The LED in the $50 robot is wired from a microcontroller output PD4 through a 340 ohm resistor into the 5V bus. That means if PD4 is low I have 5V differential, so V=IR so I=5/340 = 14.7milliamps. The LED (says digikey.com) is rated at 20milliamps, so that means it will light up, but a little dim, right? Digikey also says it is rated at 1.8V - does that mean sending 5V through it will blow it up?
4) Is it bad to discharge a capacitor by shorting it? Is it bad to depower my circuit but leave my capacitor charged up for a long time?
5) The big capacitor on this $50 robot - that's the one that is protecting from large power draws from reversing the servos, correct?
6) What's the little capactor for (the one between ground and 5V)?
Thanks, and sorry if any of these questions are obvious!