Common GND with Buck Modules?

Using Arduino General Electronics
1

I am creating a LED lighting unit for an Aquarium and I have a 240vAC to 24v DC power supply.

I want to output 12V and 5V also in addition to the 24v DC.

I have 2 buck modules - like these modules off ebay set to 5v and 12v from the 24v input.

Measuring the DC on the output side I get the correct voltage from the output + and - connections.

My question is in my project I have a need for a lot of 5v and GND connections.

Can I just join all the GNDs together?

Will this work or is this a stupid thing to do? What would happen?

The 12v device is an Arduino and the 5v device will be connected to the arduino pins.

2

It appears that this is OK....

3

You have more grounds than you need. Those Dc/DC modules are not isolated therefore the ground in and the ground out are the same signal.
I would try removing the grounds from the output side of the DC?DC converter.

4

Grab your 24VDC to 5VDC converter module...... then get your multimeter. See the two negative terminals? If you use your multimeter to measure the resistance between those TWO negative terminals..... and if that resistance is very small, then it would mean that those two negative terminals are already electrically connected together (internallly). If they are internally connected already, then you don't need to connect both of them back to the common ground (since one is already linked to the other).

So maybe it could end up like....

Uh6Bf.png