Re: Question about AC power distribution in CNC controller box

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "mrgamber" <mgamber@c...>
wrote:

>
> Nowhere did I say I intended to tie the 2 power inputs together...

I

> don't understand why this became the understanding.
>
> My intent is to supply the controller board and 2 low power AC
> devices (switched with solid state relays) with one 120v 10A power
> entry module and then power the 120V transformers (motor power
> supply) and the spindle with a completely seperate 120v 15A power
> entry module. Line and Neutral will NEVER get near each other...
>
> The question is how to ground the two 120V seperate power inputs.

Do

> I put 2 ground posts or 1? I fail to see the difference between
> having 2 boxes, each with their own ground posts but the chassis
> bolted together vs. 1 box with two ground posts to the chassis.
>
> I think the safest option is to have a box within a box for space
> saving purposes, while still keeping some physical isolation

between

> the two AC inputs, but electrically, this should be the same as 2
> ground posts in one box. Right?

I think one could just get a correct defination of the term 'ground'
as I understand, it is the Earth. all grounds in a residentual house
wiring will be tied to a metal post driven into the earth, er.. some
use water pipes when wells are involved....

Your typical American house has 2 lines, with a potential (voltage)
of 220 volts between them. and a potential of 110 volts between
either one and ground. that said, every ground in your house is
common to that metal bar driven into the ground.

In my unit, I have the PC, with 12v, 5v and reference ground that go
to my breakout card. the parallel port cable shares the same ground
and also goes to the card.

That card is in my power supply enclosure along with my Gecko's and
some PCB mounted relays on the breakout board.

A third enclosure contains my relays. they are powered by 24vac in
that enclosure and the mini relays mounted on the breakout card use
that 24 volts to switch those relays.

spindle voltage and solenoids are 110 vac from that third box.

My residential wiring is to one wall recptcle and all things,
monitor, PC, power supply and spindles all share the same earth
ground, house wiring ground and also the same phase from the utility
company.

No problems with it so far.

Dave