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Author Topic: Voltage Levels on Analogue Input  (Read 472 times)
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Hi,

If I'm using an Arduino Skinny or Arduino Wee (ATMEGA168V) where they both run on 3.3V, can I read a signal up to 5V on one of the analogue pins?

Thanks,
Jules.
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As far as I know, the maximum analog level you can read is the supply voltage.  You can use AREF to lower the range below the supply, but you can't raise it above.
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From page 304 or section 28.1 of the ATmega168 datasheet, the ATmega is rated to it's supply voltage +0.5V on any pin WRT ground.
Quote
Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent dam-
age to the device. This is a stress rating only and
functional operation of the device at these or
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect
device reliability.

You can ofcourse use a simple voltage divider to divide the 5v signal into something in the 3.3 volt range. Obviously the tolerance of the resistors will impact the accuracy of the ADC.
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