portable, battery powered and software adjustable regulated power supply.
Do you think this would theoretically work?
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First I like the art!
(no expert) I think it will not work, scenario: at start-up
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If Arduino gets too little power I wil not do anything so it will never get enough power => stays "dead" but undamaged
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First thing to do is to start the Arduino, and if it is running it could start the "power supply" but that may cause a voltage drop (going to scenario 1 ?)
But then again I'm no expert.
"in theory there is no difference between theory and practice, but in practice there is ..."
- If Arduino gets too little power I wil not do anything so it will never get enough power => stays "dead" but undamaged
Well it may not work (I would guess not, but for no specific reason) but not for that reason. His Arduino is getting power directly from the battery pack. The output of this proposed 'programmable regulator" is the blue wires going off the page, this regulator doesn't power the Arduino.
As far as if it will work, you can only experiment and see. I don't see any risk to the Arduino board as you are using a voltage divider for the Arduino analog input pin.
Art work is cute, but a real schematic would be a treat. 
Lefty
[edit]On second thought I'm sure it won't work. There is no voltage being applied to the gate of the mosfet from the collector of the npn transistor. This is a semiconductor fail. ;)[/edit]
On second thought I'm sure it won't work. There is no voltage being applied to the gate of the mosfet from the collector of the npn transistor. This is a semiconductor fail.
Why is that?
Well you have the Arduino switching the base emitter junction of the npn transistor, but there is no voltage on the collector to switch and it's connected to the gate of the mosfet that requires a voltage to turn on. So you tell me what voltage do you expect to see on the gate of the mosfet and where does it come from? Remember semiconductors don't generate a voltage they just amplify or switch externally applied voltages.
Lefty
It switches the negitive voltage which should trigger the mosfet based on the positive voltage on its source.
Well time best spent if you just build it and prove it works, I'm not really a qualified instructor for semiconductor fundementals, I'm just certain it won't work as drawn. If that is a standard N-channel mosfet, then the gate has to be at or greater then +10vdc higher then the source to allow the source drain junction to fully conduct.
Lefty