Again, a grounding question.

My project has a 7 V battery that feeds 2, DC to DC , 2596 voltage reducers… 1 is 3.5V and the other is 6.0V.
I have attached a rough schematic to which I have a few questions.

I have read the articles here about making a complete circuit with hooking the grounds together and I understand ground to to be any minus (----), from a battery or my 2596 devices. So here I go.
A) Can I or should I tie the 3.5v and 6v ------- together ?
B) wherever the circuit calls for a connection to ground, can I use any of the ------ posts. Either the 3.5v, or 6v, or even
the 7v battery ?

Well, I tried to do an inline image and I can’t do it from this machine.
Very sorry

The grounds are connected back at the battery already.

I saw that Larryd and wondered about it. But I was not sure.
For my feeble understanding, I presume that whenever I need a connection to ground, I can connect to any of the neg.
points. Is there any difference in the 3.5v neg or the 6v neg or the 7v neg ?

Thanks

I think you will find the negatives are tied together.

With the power disconnected, you can use a DVM to confirm this.

Look closely at the bottom side of the converter PCBs and you should see a foil path from the input GND to the output GND.

Is there any difference in the 3.5v neg or the 6v neg or the 7v neg

They are all the same point so all have the same potential so to a first approximation it doesn’t matter what you use.

There are some circuits however that are sensitive to the ground paths. For example when switching a heavy load like a motor or lots of LED and getting information from sensors. In these situations you should have one ground point and wire everything to that point, that is, not chain them or allow ground currents to mix that is to share the same path. Just like Ghost Busters, don’t cross the streams.

Grumpy_Mike:
Just like Ghost Busters, don’t cross the streams.

Unless it's the real big boogey!

In principal it should work and that is the way to connect things ....but some converters will not work if the input negs are tied together and the output negs also due to the way the internal circuits operate.