Measuring voltage causing power supply sourcing issue

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i measuring/monitoring voltage of 5 volt supply using a6 pin of nano. worked fine until needed toggle power of nano. when remove 5volts on vin line nano stays powered !!!! way can shut off nano removing 5 volts a6 pin. should happen ? if how can prevent voltages on analog inputs powering nano ?

do not apply external voltage exceeds supply voltage pin directly - back-power board through protection diodes, exceed rated maximum current through protection diodes , potentially damage arduino. how blow pins.

if can't arrange voltage not present on pin when board not powered, put 10k resistor between analog pin , external voltage; keep current low enough prevent damage.

if put 5v onto vin pin, you'll 3.something on 5v pin - vin goes through regulator, has minimum dropout of 1.something volts. if supplying external 5v, need put on 5v pin, not vin pin. if supplying via vin pin, need give @ least 7v 5v out.


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