Pin doesn't set to 0v

Hi guys, i have a dude regarding to the behavior of a digital pin. I run a simple code that set all the pins to LOW, nothing special, but when a measure the pins 3 and 4 (with a voltimeter, one lead to the pin and the other to ground), i dont get 0V. Instead im getting 0.82v. In the others pins, i measure 0V.

I dont know if this is normal or if these two pins have some troubles.


Did you set the pins to output as well?

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What model Arduino controller?

Thanks.. Tom.. :slight_smile:

Is nothing else connected? Just the multimeter?

FYI - 0.82V is a valid low (with a 5V power supply). According to the ATmega datasheet, output-low can be as high as 1V. And, an output-high can be as low as 4.2V (with a 5V power supply).

On the inputs, anything greater than 3V is read as high and anything less than 1.5V will be read as low.

Note that the input has a tighter undefined range so a valid output state is always read as a valid input state (when connected to another compatible chip).

Im using the arduino uno and yes, i declare those pins as ouputs. Just the multimeter was conected when i did the measurement.

I'll be using those pins in the base of a transistor and i think that little voltage will give me trouble.

P.D: Sorry for post here this topic..

Change the battery in your meter.

If you are driving a transistor switch you will need a series resistor anyway - so it shouldn't be a problem . If you wanted , out a diode in series to the transistor base ( plus the resistor) , it will defenitely be off then

An unloaded pin set output and written low should be much closer to 0v than that...

Place a 1K resistor between pin3 and gnd, then measure the voltage on pin3.

Thanks.. Tom... :slight_smile: