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GibbonsRock
07-19-2008, 04:38 PM
Hi!

I'm wiring a Keling kit up and I have a question. Is it OK to connect all the grounds together from the 5v and the 36v systems? (The 5V is coming from the computer's USB)

Does it matter if I wire up the 36V power supply with two wires or three?

Sorry for the rookie questions, but I may have blown up a HobbyCNC board with a grounding issue, but HobbyCNC was not helpful in troubleshooting it, so now I'm pacing my steps carefully.

Thanks! -Jim

LeeWay
07-19-2008, 06:20 PM
I'm pretty sure those grounds need to stay apart. I have a lab supply and it produces 2 x 32 VDC both with seperate grounds and it has another 5 VDC that is separate again.
You sure don't want your higher voltage PS having a common ground on the PC.

There are several ways and many theories on grounding, so you may get a different answer as well.

Al_The_Man
07-19-2008, 09:25 PM
The term ground and common are frequently mixed up and interchanged.
One does not necessarily mean the other.
There are two schools of thought, some specify complete isolation, i.e. all systems and power supplies kept separate by isolation.
The other where all components of a system, including all metalic objects/enclosures power supplies, shields, are connected to an earth point, common to service ground etc.
This is called uni-potential bond/grounding.
Once a method is selected, it should be carried out in the correct manner, many problems occur because one method or the other is not adhered to completely or correctly.
I prefer the latter because it is usually easier to achieve.
Al.

GibbonsRock
07-21-2008, 08:39 AM
Very interesting. I asked because there are two wiring diagrams on Keling's website, and one shows all the grounds connected, and the other keeps them separate.