Gotta keep busy while the e3d’s in customs…I just wish the RUMBA had a 5v USB power output. It’s got plenty of juice going into it from the ATX power supply, I just don’t want to get my ugly soldering skills going on a power feed for the Pi. Having a single power cord and a spool of filament being the only non printer things appeals to my inner OCD…and yeah, I’m ignoring the power supply. Sometime soon I’ll carve off the un-necessary loom…probably when I can print a plug for the hole it comes out of.
There is a 5v output pin on the RUMBA, at least you’d only have to worry about ugly crimping skills there.
“Mental note, this therm jumper cable is PI power, not a thermistor…” 
+1 for ugly soldering skills and inner OCD! 
Just a thought, perhaps you’ve already considered, what are you trying to achieve with the 5V from the rumba?
Could you use a 12v line from the rumba and use a relay on that 12v line to switch your 5v circuit? (I’m thinking of setting up my ‘fan’ output (the only one I can sacrifice) to a relayed circuit, then I can send M106 (fan on) to turn the relayed circuit on / off)
Thinking that even got me wondering if an arduino could pick up on the PWM of the fan and do different things (ie, if you want to drive 4 different fans you could have it set up so that fan 1 comes on at 0-25 PWM, fan 2 comes on at 25-50 PWM and so on… Anyone know if that can be done?
There’s a power switch on the power supply controlling all power to the system, it’d kinda be a cart before the horse having the Rumba turn on the Pi (unless I’m missing something obvious)…of course, I’m not sure what kind of power transients might be introduced, that’s where my experience is a little short in this area.
Of course, it’s at this point I realize, I never mentioned I was using the Pi to run Octoprint to control the printer…
Oh! how is that setup? I’m considering that, just found out about octoprint 
Ok, so the 5V is for the pi, can you not get that from the ATX supply?
I can, but I’d rather have a single 12v +/- cable going into the printer…since I’m using a molex plug, I could conceivably use the 5v from it…still kinda wanna just run 5v off the rumba.
Octoprint seems to work pretty well, I had issues that may well have been my wireless base station, and the Pi gets overwhelmed when you try to do a phantom print and the Rumba is screaming “COLD EXTRUDER, EXTRUSION PREVENTED!!!”
Coulda got one from Filastruder (http://ww.filastruder.com) - no customs! Good if you need any spare parts, at least.
Now THAT’s some OCD!
Lol - my earlier comment about turning on the fan signal to TURN ON the pi (which is the unit that would be SENDING the “turn on fan” signal)
facepalm
Wasn’t that well thought out was it 
How much power does the pi need?
If u can fit it u might be able to get a “car cigarette lighter USB charger” (search on eBay) and insert it into your base, connect 12v line to it in parallel with the machine and viola! U have a 5v USB port up to 2 amps (from memory)
I’m going to hold onto that idea actually
I like that! The fact the sacrificial cable I bought for this aspect of the project included a car adapter makes it even better. (and it’s fused)
yeah I am using my android with @Mathias_Dietz 's gcodeprintr occasionally and it would be good to charge it without bringing a USB charger in each time