Ultimate guidance to avoid Electromagnetic Interference

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23 Oct 2021 17:59 #224006 by shpatb
Here is what my machine looks like now . , i learned a lot from this journey of  dealing with interferences.
For everyone that is a beginner and plans to build a plasma table shielded cable is a MUST.
Huge thanks to Tommy for helping me out ,and everyone of you guys that keep this forum a good place of learning from each other experiences .
i attached some pics of the machine and cuts  with my new plasma cutter  stamos s85.
warm greetings Shpat.

 
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23 Oct 2021 18:16 #224007 by rodw
So you got rid of a HF machine and replaced it with one designed for CNC  I see. I'm sure that and your changes will solve your reliability problems.
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23 Oct 2021 18:19 #224008 by shpatb
Yes and Yes.:))))))))
Thanks for Your help!
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23 Oct 2021 23:29 #224042 by tommylight
Pretty sure both of those plasma sources use the same pilot arc, actually i would bet on it.
This one just has a smoother start, seems almost like it starts low and gradually ups the voltage.
Now everything has it's own power supply (Mesa 7i92 is powered by a 5V 40A power supply!!! ), is isolated and wired properly, shielded cables properly grounded, etc.
Definitely was a nice experience working with Shpat, and as he offered several times to help me with my stuff, i am sure i will call him, soon ! :)
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23 Oct 2021 23:33 #224043 by rodw
Yes, I think it once again confirms that building a plasma cutter is not really an entry level sport. You have to pay attention to the wiring right from the start and you can't really skimp on the plasma machine either. I think with the benefit of hindsight I would have built a different machine first up! But Phills QTplasmac is really a shortcut now..
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24 Oct 2021 00:46 #224052 by tommylight
It would take days of typing to write down my experiences with people building cnc plasma machines and messing stuff on the way, but always, always will have interference issues and plenty of burned stuff as a result, one of them would literally try to dismantle itself shaking violently every time the torch would start as it had 7NM Nema 34 geared motors !
Luckily we had a nice incident doing Shpat's machine, used a buck/boost converter (never used this type before) to power the input relays with 5V from a 24V supply that also supplied sensors. While testing and repeatedly firing the torch = all is good, do a test cut = smoke ! While Shpat was yelling "fire, fire" i was looking at what exactly was giving up the ghosts and calmly turned off the power, changed the buck/boost converter to a buck converter i used on all my machines and i know it works properly = everything works properly.
After some thinking that evening i came to the conclusion all that was not from interference so the next day i opened another of those new buck/boost converters and attached the already damaged relay board as 3 of the relays are still good, did a lot of clicking and nothing, all 3 relays would happily click one at a time so i just ran a piece of wire connected to ground through the inputs so they would rapidly turn on and off and what do you know = the lab power supply triggered current limiting!!! Those pieces of $h1t get stuck at 31.5V output when powered by 24V and used as buck after about 10 to 15 times of switching inductive loads!
All this is very important for me (i did say a nice incident above) as i have all my machines using buck converters that work perfectly, but the last order was for all buck/boost ones as i thought more versatile, this could have cost me wayyy more than a relay board!
Me glad, me very glad! :)
The following user(s) said Thank You: phillc54, Clive S, shpatb

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