ADC in Atmega48

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Hi guys,

I'm planning to use the atmega48's internal ADC to do some analog conversion , however the analog signal that i wish to sample is as high as 12V !

and the rating for a pin in the mircocontroller is around 5V (the supply voltage to the mc).

is there a way to sample this 12V with the mc's ADC ?

thanks for ur suggetions !

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Make a voltage devision with to resitors to make your voltage under measure level

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If you make the divider values too high the a/d will have poor accuarcy (which can be solved to some extent by adding a cap after the divider to rid the a/d sampling noise (but not its leakage current).

you can add an opamp buffer to the a/d as well which will allow you to use large values for the divider resistors & not load down your signal source (if it is weak).

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