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.

Thanks.

Did you set the pins to output as well?

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html

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...

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

Thanks.. Tom... :slight_smile: