Connecting 120VAC ground with Arduino ground

My project, a CNC type machine has a Mean Well 24 VDC power supply. My Arduino runs off 5 volts, coming from a roboclaw motor controller. I have limit switches 15 feet out, on the head, which also has AC and DC motor wires running thru the same cable chain carrier. I was having trouble with my Y axis home limit switch being tripped occasionally, when energizing the motor out on the head. I swapped out my limit switch wire for a very good shielded 2 conductor cable. That fixed the problem, even without connecting the outer shield to anything. Then I went ahead and connected the shield wire to the ground wire inside it which would be the ground coming from the Arduino itself.
I'm wondering about the Arduino ground, and the earth ground, like the chassis of my CNC machine. Would it be best to connect the shielded jacket to the arduino ground, the earth ground, or both. I currently have the shielding connected to my arduino ground and if I read the voltage across it and the chassis I get like .3 volts. I think that just phantom voltage as if I put the grounds all together nothing adverse happens.

I'm just wondering what is the best of normal thing to do with the shielding jacket on low voltage wiring for microswitches on a CNC machine?

Hi,

You are making a significant industrial machine and you need to learn all about shielding and grounding and suppression of Electromagnetic Interference. Ideally you should be planning this physically and electrically at the beginning of the design process.

To begin with, understand "Common Ground Point". There should be a single point (probably the chassis of you machine) with a good grounding terminal block. To that should be connected (with separate wires!):

  • The negative terminal of your power supplies
  • The Arduino Ground
  • The ground terminals of your actuators etc.
  • The Safety ground (Green wire) of the main power cable that supplies power to your machine
  • Other individually-powered components

.

You should consider slowing down (a few milliseconds) the signal from your switches, with a series resistor and a capacitor to Arduino ground. 1000 ohms and 0.01 uF to start.

Generally your switch/sensor shields should have one end grounded at the Arduino

Some info HERE and HERE

Please let us know how things are working, what you did and what problems you find.

Anyone else have pointers? IsThere a good write-up of this on the web?? I / We should get one together for the Arduino environment.

Thanks. I'm double checking all my grounding, now.

You should consider slowing down (a few milliseconds) the signal from your switches, with a series resistor and a capacitor to Arduino ground. 1000 ohms and 0.01 uF to start.

After working all day on checking grounds, replacing wiring with better shielded wire, I still occasionally got a little blip on the Motor home microswitch. But adding this decoupling cap to the input of it fixed the problem! Thanks so much.