I'm in the process of adding a raspberry pi to my eggbot, so I can do long jobs like engraving without tying up my laptop the entire time. So far the setup has been pretty straightforward, but I have a couple of enhancements in mind for the future.
The first is I'd like to reduce the cables by possibly running the pi off of the power from the ebb. I see LOTS of places to take 5volts off of the ebb, but it's not at all clear to me that it can provide enough current on the 5 volt "rail".
1 ) Does anyone have any experience with powering anything else off of the 5 volt connections and have any advice?
2) The ebb schematic has the note that "IC 5 is only good for 1 or 2 servos worth of power" but there is room for four servos. I've looked at the datasheet for the voltage regulator and it has left me scratching my head, unclear about how much current it can handle, but I doubt it will be enough for the 700-800 mA I expect the pi to use while still driving both servos. Or am I being too cautious? I see on the back of the board that it references an alternate power source for the servos, with a place to solder another jack, but that doesn't help with my goal to reduce the power cables to one. If I replace that voltage regulator with one that can handle more current, are there other gotchas that would preclude running the pi off of the the servo rail?
3) I see that the alternate power supply connection disappears between version 2.1 and version 2.3, is that because no one used it, or was there something wrong with using it? Since the connections for the other two servos are still on the board, is there any way to power them with version 2.3? (this is just curiosity, knowing the answer probably won't help my project.)
4) Maybe what I should do is just add my own voltage regulator to change V+ (the power from the barrel jack) to 5 volts for the pi, and leave the servo regulator alone. But I'm not sure where to get it from short of soldering to the jack itself. Is there a handy way to tap into V+ on the board that I've missed?
The other thing I wondered about was automating frequent jobs. When the inkscape plugin talks to the eggbot, is it a two way communication, or could the commands be saved to a file and then played back later?. i.e. is the conversation like this?
PC: Here are a bunch of commands. Do this, then this, then this, then this, etc.....
Or is it like this?
PC: Do this
Eggbot: OK, done
PC: now do this
Eggbot: OK, done