Adafruit Industries, Essential service and business: NYC – Executive Order 202.6 - Read more.
0

Connecting DGND to GNDA
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Connecting DGND to GNDA

by mtangy on Wed Oct 05, 2016 3:49 pm

I plan on using my beagle bone to control a relay module and take measurements from a analog temperature sensor at the same time. I have a separate 5V DC power supply I plan on powering both the temperature sensor and relay module with (Im also using a 2A power supply to power the beagle bone). I plan on creating a common ground between all components and I'm wondering if its ok to tie DGND to GNDA.

mtangy
 
Posts: 21
Joined: Wed Dec 23, 2015 2:09 am

Re: Connecting DGND to GNDA

by grahamh on Fri Oct 07, 2016 5:01 pm

It depends.

The two grounds are tied together inside the Beaglebone.

But they are provided separately for external connections for a reason.

If you using both the analog inputs and sharing the same ground wire or system with DC power, then any DC current or noise currents flowing in the DC Ground will be superimposed on the (small but real) resistance in the ground system and appear on your analog inputs.

So, it is a potential source of noise or DC offset errors in your analog input.

If the offsets and noise are so small, that it does not matter, then go ahead.

If you are in a situation where you must share grounds, keep the resistance in the shared ground between the remote sensor and the BBB as small as possible.

--- Graham

==

grahamh
 
Posts: 3
Joined: Thu Dec 19, 2013 10:57 pm

Please be positive and constructive with your questions and comments.