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Topic: Maximum Current/Voltage into an analog pin on an Arduino Uno (Read 22858 times) previous topic - next topic


What is the maximum voltage and current that I can input into an analog pin on an Arduino Uno? The Uno website says:
- Input Voltage (recommended): 7-12V
- DC Current per I/O Pin: 40 mA

Is this correct?



7-12V is the maximum input voltage you can apply to the external DC input power jack.

The analog input pin voltage is limited to 0V-5V. Anything outside that range will damage your microcontroller.

And to clarify, you do not "input" current into a pin. The pin decides how much current to draw in response to an applied voltage. If your applied voltage is in the range 0V-5V then the amount of current that will flow into the pin is very close to 0. Just make sure you configure the analog pin as an input, and not an output.

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If you are using the pin as an output , make sure to use an appropriate current limit resistor to avoid sinking more than 40mA (absolue maximum) when driving an output low, or sourcing more than 40mA when driving an output high.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Feb 12, 2011, 06:42 am Last Edit: Feb 12, 2011, 07:00 am by Sonia Reason: 1
Thanks for the clarification guys! I just have one more question, when defining the analog pins as input in the pinMode function, am i referring the the analog pins as A0, A1.... ie:

pinMode(A1, INPUT)



If you are only using the analogue inputs as analogue inputs then simple don't do anything it gets set automatically. If you are using them as a digital input or output then use pin number 14 for A0, 15 for A1 and so on.

The 5V input limit only applies to an arduino that is powered from 5V, lower voltage arduinos like those that run from 3.3v then that is the limit. This applies to not only analogue pins but also to digital pins.



Hello all,
One more clarification please. I am building a 10 step resistive divider across the Uno 5v and gnd. Is it safe to apply the "5v" end of the string directly to the analog pin for a 'analogRead()'? If not, what size resistor would be suggested for a limiting resistor (resistor # 11)? The Uno is powered by the USB input.


"If it ain't broke, fix it 'til it is". (unknown)


Yes, for a 5V Arduino such as an Uno, 5V applied to any pin is safe.
GoForSmoke: "What GShield? You never mentioned a shield."


Thanks Morgan. Now I don't have to worry about filling the shop with smoke. :smiley-mr-green:


If you have to measure "something" that is 5volt, use a resistor between that source and the input pin (4k7).
Just in case the Arduino is off, and the other device is on.
That limits fault current to 1mA.
Not needed ofcourse if the 5volt comes from the Arduino itself.

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