Putting mesa cards and PSUs in the same enclosure – yay or nay?
- Twizzlermill
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so, with all the cables having shielding ( is that the right word? I mean the metal mesh/foil wrapped around the wires to prevent electromagnetic interference), I wonder where exactly to start with this. I know, it's supposed to eventually go back to ground, but if I want to connect up drivers and card, I need to untangle the wires at some point, to get them in their respective sockets/pins. Also, I guess if the other cables are a problem, the stuff that they are there for seems like a problem as well, no? Like PSUs, mainly. Getting a metal housing for the electronics rather than a plastic one seems like a good start, but after that, I'm not so sure. Should I isolate the Mesa card from the PSUs? Or does it not matter that much? If yes, should I go for a separate enclosure? Is there an established way of doing this? Am I overthinking stuff?
TIA,
Twizzler
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- BigJohnT
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JT
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- Twizzlermill
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However, I'm not sure I understand this part:
Maybe it's a language issue (I'm a non-native speaker, mix in technical jargon and it's… worse), but I'm not sure which part 0vdc refers to and what floating ground voltages are exactly.Power supplies 0vdc should be tied together so no floating ground voltages are present.
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- bevins
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The power supplies common or 0v should be tied together so to have a reference so they are at the same potential.Thanks for the answer. Yeah, not grounding the shields at both ends is something I've heard of, thanks for giving me an explanation as to why.
However, I'm not sure I understand this part:Power supplies 0vdc should be tied together so no floating ground voltages are present.
Maybe it's a language issue (I'm a non-native speaker, mix in technical jargon and it's… worse), but I'm not sure which part 0vdc refers to and what floating ground voltages are exactly.
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- Twizzlermill
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In another built somewhere, I've read that you should always "collect" all your ground cables at a central point (i.e. tie them together?). Is that what is meant here?
Sorry if I'm asking basic questions.
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- rodw
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I thought best practice with mesa was not to connect 0 volts to the frame ground and therefore to keep the field power isolated.
I did have issues with noise and I fixed that by replacing my IEC mains connector with one that had an EMI filter built in as the noise seemed to be entering via the mains ground. But my machine is a plasma machine so noise abounds!
My next enclosure will feature 60V AC toroids and I am thinking of adding a steel partition between the mains power section and the rest of the enclosure.
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- tommylight
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0V or common is the -V on the picture, so if using multiple power supplies the -V should be tied together, although that is not always the case, when using isolated electronics like Mesa 7i76 or 7i77 the 5V logic and 24V field should not be tied together as that would void isolation.
Also some power supplies will have the -V tied to ground and that is in most cases ok for the field side.
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- rodw
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Ground is the power grounding wire, usually green and yellow, and it literally has to be tied to a ground rod somewhere around the shop/house.
0V or common is the -V on the picture, so if using multiple power supplies the -V should be tied together, although that is not always the case, when using isolated electronics like Mesa 7i76 or 7i77 the 5V logic and 24V field should not be tied together as that would void isolation.
Also some power supplies will have the -V tied to ground and that is in most cases ok for the field side.
Except if you are using the Mesa MPG's on say a 7i76e, and you do power the 5v side seperately, you do need to tie the 5V and 24V grounds together...
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- tommylight
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And there are cases when that might be required, but to many examples make for a confusing post and has nothing to do with how i explain things !

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- Twizzlermill
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Just for reference, this is what I need to connect up right now:
Mesa 7i76E card
4x JMC closed loop steppers
2x 36V power supplies for the steppers
1x 24v power supply for the card and maybe fans for the enclosure
1x 5v power supply for the card
fans (here I'm not sure whether I want to put another 12v PSU in there just for them, because 12v fans are way more common, or get 24v fans)
2x wall power sockets for shop vac and spindle
Also:
Endstops
tool length sensor
Power Button/Emergency off
For now, I won't fuss with relays for the vac and spindle, but it's planned down the road.
So really at the moment, in the enclosure will just be a bunch of PSUs and the Mesa card I guess.
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