Lets Talk Wiring And EMI

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11 Jun 2019 21:57 #136668 by tommylight
Replied by tommylight on topic Lets Talk Wiring And EMI
No problems at all. I did my fair share of such installations with the difference that I did that on working computers, so it was all in a single box, although to much wires.
The only empty ones I used were a small shuttle PC and had the same PC so they looked nice together, still do after nearly 5 years with a lot of dust on them. The other empty one used for some time ( it is empty again in the workshop waiting patiently ) is an Apple G4 that I gutted to use the box for electronic. It was in perfect working order, just had a slight issue of drawing nearly 600W of power to work. That was to much since my other PC at that time did 450W and was twice as fast.
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26 Jun 2019 17:58 #137919 by flamecutter
I've also had some experience with EMI on the stepper drive plasma table I built.

It seems there is an abundance of advice on the subject (some conflicting). I have found the attached article to have a good overall view of the subject. To deal with the problem I ended up installing a shielded isolation transformer, which mostly took care of it.

I still have some conflict with my high frequency start tig welder. Sometimes if it is being used at the same time as the plasma, it will cause some erratic moves. I'll acknowledge that because of my shop size, my tig welder is just too close to the plasma (about 15ft.).

Otherwise I have very little problem with EMI.
E.W.

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26 Jun 2019 23:10 #137939 by tommylight
Replied by tommylight on topic Lets Talk Wiring And EMI
The amount of interference produced by HF/HV start plasma and TIG as they use the same thing is impressive , but it is very hard to explain to people who do not deal with it as it can not be seen.
Proper grounding is a must, shielding on cables also, but sometimes just changing the mouse or the keyboard will do the trick nicely. Until recently I could find used Dell or HP or IBM keyboards and mouses and they were very good, especially the IBM ones as they are the best keyboards to type on, but they are getting hard to find, so now I tend to use Genius or Logitech, and also found some very cheap ones with proper shielding that work with plasma, they were 4 euro a piece and got 3 of them, now I can not find them anymore.
Also USB extension cables can cause issues, find transparent ones so the shielding can be seen, also found one such type that looks properly shielded but caused issues and after checking with DVM it turns out the shielding was not connected to any of the connectors !
Oh and please no roled up wires/cables, that might look good, but it is terrible for collecting interference .

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29 Jun 2019 14:25 #138176 by Surfermann
Replied by Surfermann on topic Lets Talk Wiring And EMI
In a recent post I asked about "Linear move would exceed Axis X's positive limit". My problem was that I was not pushing the Home button.

The longer story, my machine was possessed (due to several loose connections in the plasma control cable). Before I figured that out, we were doing everything we could to fix the problem, including eliminating any possible noise source. In the process, since I didn't need them with my workflow, I eliminated my Y axis home switches as that eliminated another set of wires (antenna) going into the control box.

I also set up a star ground with an earth ground. The dilemma for me was that we could only drive the ground rod about 4" deep before we hit rock. We even use a jack-hammer to drive it down. We make sure that several times a week we dump a bucket of water on the ground rod so the dirt remains wet for adequate continuity.

So while my machines possession was not caused by noise, I've at least taken all reasonable steps to reduce EMI.

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29 Jun 2019 17:41 #138183 by pl7i92
Replied by pl7i92 on topic Lets Talk Wiring And EMI
hi we run 5 Plasmas in a shop
Most time EMI is efecting it is simply a loose or non good Plasma table to Torche Ground
as many dont like to clean the table on workday end or after a real hard cut

i never got any problem on Cable
we use for steppers Double shielded Robot cable outer ground to mashine
inner Ground to control

the homing is standard single shielded chain cable 2x0,5mm²
as we use mainly Me-8111 switches

ot the LJ12A3 BX induktive NPN NO with 12V that takes the emi to Vanpower and not furthere

Main issue is the House grounding or shop plasmas may requirer a shorter cable
WE did drill at every plasma to the ground 10mm Hole and put in a 2meter iron to MOTHER earth
as well as the Airpipes are grounded

the control is in the same cycle as the 400V plasma only the PC is on a other line within the shop

Ironicly if the Powersuplyer changes Phases on the City line it may fail as here all out as torch start
realy it blowes out the PC and shop lights go of on

then i did change the UVW to VUW and all is good again till the next power swap

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