What Arduino ground pin to wire to existing circuitry

Dear all,

when integrating Arduino as PC interface into an existing circuitry for DIO, PWM out and Analog in, do I need to connect the GND pin next to 5Vcc or GND pin next to the DIO pins or both Arduino GND pins to the circuit common ground?

Thanks Holger

As far as I know, "ground is ground" and they're all connected together anyway... you could check that easy enough with your meter.

Thanks - I'll check this. To avoid ground loops I will only use one ground connection from the Arduino to the external circuitry. Holger

All the grounds connect to the same ground plane - solid mass of copper - on the board. It doesn't matter which GND you use, they are all the same.

Thanks :)

"solid mass of copper " Not really - is full of holes for thru holes, SMD pads, vias, traces, etc. If you use eagle and look at the actual top & bottom layer you will see it is not very solid at all. But it does cover the top & bottom layer where nothing else is.

CrossRoads: "solid mass of copper " Not really - is full of holes for thru holes, SMD pads, vias, traces, etc. If you use eagle and look at the actual top & bottom layer you will see it is not very solid at all. But it does cover the top & bottom layer where nothing else is.

Congratulations, you have earned the title of "Which Tyler" - Leader of the Pedant's Revolt.

Compared to traces it's a "solid mass of copper". In the same way that I am a "solid mass of blubber" - yes, there are bones and organs in there, but the majority of it is blubber.

Oh, and the vias and through holes join different sections of the ground plane together using... guess what ...? Copper. The ground plane, despite being a convoluted shape with other things going through it is, despite what you may thing, a single solid entity with no breaks in it. Yes, it goes around other things, but it is unbroken. If it weren't then it wouldn't be much of a ground plane now would it? It would be 17 ground planes with nothing connecting them :P

If you have any sensors in your design that are connected to analog inputs, then it's a good idea to dedicate one of the Arduino ground pins as "analog ground" and use it to connect the ground sides of those sensors. Use a different ground pin to provide power (if power is not coming from the USB port or barrel jack) and to connect the ground sides of any output devices. That way, power supply current and output ground current doesn't affect the sensor readings so much.

That way, power supply current and output ground current doesn't affect the sensor readings so much.

Even though they're electrically connected? Interesting...

Congratulations, you have earned the title of "Which Tyler" - Leader of the Pedant's Revolt.

No that is Wat Tyler, so do I get it?

http://en.wikipedia.org/wiki/Wat_Tyler

Maybe you are thinking of Wat's younger brother Which Tyler, he went on to lead the middle class revolt, founding a consumer magazine that is still around today http://www.which.co.uk/

In the same way that I am a "solid mass of blubber"

I am sorry about your personal obesity problem especially as you don't appear to be human.

Blubber is the thick layer of fat under the skin of marine mammals, such as seals, whales, and walruses.

according to http://education.nationalgeographic.com/education/encyclopedia/blubber/?ar_a=1 So "cu cuch tue" as John Lennon would have said.

The ground plane, despite being a convoluted shape with other things going through it is, despite what you may thing, think a single solid entity with no breaks in it.

You obviously know little about topology as well. http://en.wikipedia.org/wiki/Topology If it has a hole in it it is not solid.

JimboZA:

That way, power supply current and output ground current doesn't affect the sensor readings so much.

Even though they're electrically connected? Interesting...

If you think about it just because things are connected electrically it does not mean there will be a current flowing. You need a potential difference to get a current flow and if there is no difference then there is no current. You get into difficulties when the same path is used to return heavy current from a switching load and very light current from a sensor are using the same path. This causes the current path to have a voltage gradient across it and it is this gradient that can effect the sensor.

JimboZA:

That way, power supply current and output ground current doesn't affect the sensor readings so much.

Even though they're electrically connected? Interesting...

Grab a scope. Connect it's ground connection to one ground pin, and probe the other ground pin. You may be surprised how much noise there is between them.

Grumpy_Mike:

Congratulations, you have earned the title of "Which Tyler" - Leader of the Pedant's Revolt.

No that is Wat Tyler, so do I get it?

http://en.wikipedia.org/wiki/Wat_Tyler

Maybe you are thinking of Wat's younger brother Which Tyler, he went on to lead the middle class revolt, founding a consumer magazine that is still around today http://www.which.co.uk/

In the same way that I am a "solid mass of blubber"

I am sorry about your personal obesity problem especially as you don't appear to be human.

Blubber is the thick layer of fat under the skin of marine mammals, such as seals, whales, and walruses.

according to http://education.nationalgeographic.com/education/encyclopedia/blubber/?ar_a=1 So "cu cuch tue" as John Lennon would have said.

The ground plane, despite being a convoluted shape with other things going through it is, despite what you may thing, think a single solid entity with no breaks in it.

You obviously know little about topology as well. http://en.wikipedia.org/wiki/Topology If it has a hole in it it is not solid.

Yep, You got me - I am the walrus.

And no, it's definitely Which Tyler. Wat Tyler led the Peasant's revolt, but Which Tyler, being grammatically correct, led the Pedant's revolt.

But you're being so pedantic I think I'll name you Which Baked Clay Flattened Plate Measuring 12 Inches By 8 Inches Roofing Material Installer.