Access to Real Input Voltage?

question:
i vin pin on arduino "direct" access external power supply? or vin pin getting power supply voltage through onboard chip?

explanation:
i using arduino drive external 5 v motor. have motor powered external batteries , controlled arduino pwm output , transistor. don't want drop external batteries design. powering arduino 5v power supply. can somehow access "real" vin (not current limited arduino) somewhere on arduino board? know there vin pin on arduino, think "real" input voltage going through chips before going vin pin, , current limited chipset. case or not? don't want burn out board drawing current.

thanks,
drew

methinks need refer the schematic.

you find "barrel jack" - 2.1 mm coaxial connector - feeds through diode "v_in" terminal on board in turn leads on-board regulator.

neither of these in way constitutes power output seem realise cannot power motor point on arduino.

it may possibly convenience if powering system "wall wart" supply "barrel jack", take power through "v_in" terminal need remember in case, through reverse-polarity protection diode rated @ no more 1 amp.

the concept of reverse-polarity protection diode might find rogue "wall wart" non-standard polarity (centre positive being standard), should never foolish connect "v_in" negative voltage.

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