ARDUINO / 3rd party / Plasma Possible Relay Interference?

Hello,
I'm hoping someone can give me some advice on a situation I've been having with an Arduino type card used to control my homemade CNC plasma cutting machine.

The card I'm using is an MKS DLC 32 version 2.1. and I know they're quite sensitive to electronic interference. If the plasma cutter is not turned on the g-code will execute its movements without issue from Open Builds Control. However when the machine is turned on it will only execute a few cuts and then stall and stop moving.

I was originally advised that the problem was my high frequency pilot arc machine, and so I replaced it with a blowback machine which is supposed to be much more friendly to sensitive electronics. However, even after I replaced the plasma cutter the issue persisted.

It then dawned on me to consider the fact that I had the small opto-isolated relay that activates the two pin trigger switch on the plasma cutter positioned inside the control panel and near the control board. I ran the two trigger wires from the machine into my control board panel where I connected them to the relay. I'm thinking this was providing some sort of pathway for interference from the machine to the control board. And that the relay was also causing interference.

I recently read that relays can cause interference and so I decided to move the relay from the control board panel to a location near the plasma cutter some ten feet away. Unfortunately the relay failed before I could test it but I have some more on order.

When I first ordered relays I ordered three of the cheap little red-board relays commonly found on eBay or Amazon. One didn't work from the get-go and the other two have failed now as well (probably from me reversing the polarity pins when I was wiring them).

I am now waiting for new relays to arrive. The relays are 24 volt and run from the 12/24 volt power supplied by the control board. A 5v signal wire from the control board activates the relay to close the business end of the switch which triggers the plasma torch.

I'm hoping when a new relay is installed that having relocated it away from the control board will make all the difference. Does anyone feel that this may have been my trouble all along?

 

Update: it turned out the relay was not the source of interference. After a great deal of trial and error I discovered the computer I was using had a failing button battery. This made it very susceptible to USB interference. I also read somewhere that an open builds user had a similar "error 31" issue and needed to move their laptop some distance from the plasma work table. I decided to buy a 50 ft cat6 cable and splice USB ends on it to extend my distance and went back to using my laptop as well. I also moved the control board box as far from the table as I could and now I'm having no more interference issues.

 

I kept reading about ways to extend USB cables and using cat6 extensions was a popular method. I thought the same as you regarding USB length limits and wondered how it would be any different than a long USB cable - but I figured I'd try it anyway - and sure enough - works great. If it didn't solve the issue I was going to use cat6 line to extend the motor wires and move the control board box further away. I do believe my MKS DLC32 card was the bigger issue as the condition showed up after moving the laptop, but moving it gave me room to also move the control board box a few more feet away from the work table and that's when the problem completely disappeared. Getting a blowback start plasma machine was a good idea too. Thanks for that suggestion.

 

Yes - I also read cat5 was a poor choice for creating extended cables. Didn't know why though. Thanks.