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Topic: When do you use the AREF pin in arduino? (Read 34392 times) previous topic - next topic

MarkT


So which reference will arduino uno take by default 1.1V or 5V or 3.3V?


When I said "(see http://arduino.cc/it/Reference/AnalogReference)" it was because it answers this sort of question.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

MiFi

If you do provide an external voltage reference to this pin you must call analogReference(EXTERNAL) in setup () before any call to analogRead() - otherwise you will internally short your reference to 5V and potentially burn out the chip.

...

You could connect an external voltage via a 1k resistor as a temperary testing setup - then the chip is safe (but analogRead() will be upto 3% wrong...)

You ought to point out, that actually the AREF pin outputs the selected voltage with a pretty low impedance, as long as AREF=EXTERNAL is not selected.

I have blown out my USB chip, since it got 5V back on the 3,3V rail, as I bridged 3,3V and AREF then, powered the Arduino before loading the sketch.

Anyhow even with the sketch loaded, one will never be safe without a resistor...

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