I am building a project that includes an analog Input and several digital Inputs and Outputs. All of them connect to ground in some way. Do I need to worry about voltage, coming from the digital outputs, going to ground, and effecting readings on the analog input? If so, how do I deal with this?

  • If you have a different power supply powering the sensors than the arduino then you should connect all grounds so that they are common. In other words the remote power supply and the arduino's power supple should have common bridged.
    – Tyson
    Mar 11 '15 at 0:44

The arduino has build in pull up resistors, it is not a residue voltage coming from ground more than a "not 100% 0 volt" resistor.

Even though there is built in pull-up resistors one can add additional resistance to the arduino to make sure it will not show a false positive.

From what i have learned, you cannot experience voltage comming from ground (if everything is properly wired), if you want to make sure. Place a diod in the direction of the power flow, to prevent this.

  • In what cases would it not be wired correctly?
    – Hoytman
    Mar 9 '15 at 20:48
  • just to give an example out of many but reversed polarity. or 2 circuit where one might have less resistance. Mar 10 '15 at 6:36

In this case I do not believe ground bounce will be a problem. I normally only encounter it on high speed PCB designs. You will get noise from the power supply(s). Any impedance induced between the ground of analog input (circuit board ground) and the sensor will give you problems. Be sure all grounds are low impedance in nature. Since you are designing the project consider and I assume a PCB, filtering the Aref pin supply with a small cap and a 100 ohm resistor. A low pass filter on all inputs will help, a small cap from the input pin to ground and feed it via a resistor. Good capacitors are very important.

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