1) The 5v standby rating should be on a label on the psu, and bigger than the consumption of the stack both rpi and arduino together, and their ratings will be on their specifications, but that would probably be max ratings and the boards will consume less. If the 5v standby rating is like 1-1.5-2a, probably should work.
2) The D1 would be reverse biased in this case, it will block, so i also think you do not need to remove it.
3) I think all the black wires are all technically the same ground, they would come from same place so there should be no difference which one you use for which purpose. Only the v+ rails would be separate. The gnd at ramps block will work as it will connect through psu with the gnd from the usb - this can be checked for continuity.
4) Usually to power up psu you need to connect the green wire to a black wire, that is to put it to gnd. I am not sure i understand where the 5v comes in. Usually when pins are not used and nothing is done to them they can have voltages like 2v or so. Which perhaps can turn on the psu (not really sure about that tho). I guess you are worried about the ps_on pin not having a default state, and then use 5vsb for that, could enable the internal pullup, use an external pullup (to 5v standby), or use a signal mosfet with a 3v3+ vth gate to better isolate the green wire from arduino pin parasitics or voltage values in forbidden region. Again not sure if that is required or not, but i think it should not be the case.
All in all i think it makes sense to me at least. Nice approach btw with using vsb. Do you plan to use ssh, and a local display manager even, or how will you connect?
2) The D1 would be reverse biased in this case, it will block, so i also think you do not need to remove it.
3) I think all the black wires are all technically the same ground, they would come from same place so there should be no difference which one you use for which purpose. Only the v+ rails would be separate. The gnd at ramps block will work as it will connect through psu with the gnd from the usb - this can be checked for continuity.
4) Usually to power up psu you need to connect the green wire to a black wire, that is to put it to gnd. I am not sure i understand where the 5v comes in. Usually when pins are not used and nothing is done to them they can have voltages like 2v or so. Which perhaps can turn on the psu (not really sure about that tho). I guess you are worried about the ps_on pin not having a default state, and then use 5vsb for that, could enable the internal pullup, use an external pullup (to 5v standby), or use a signal mosfet with a 3v3+ vth gate to better isolate the green wire from arduino pin parasitics or voltage values in forbidden region. Again not sure if that is required or not, but i think it should not be the case.
All in all i think it makes sense to me at least. Nice approach btw with using vsb. Do you plan to use ssh, and a local display manager even, or how will you connect?
