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!