DIY electromagnetic shielding (CNC mill)

Question

I'm building a DIY CNC router. I'm running at a low RPM and only planning on cutting soft materials (wood and under, maybe a PCB).

I'm currently having problems with magnetic interference. When starting the spindle, hard end stops would trigger, and sometimes my controller (arduino) would become unresponsive. For now I've turned off hard end stops, while building the rest of the machine. I'd like to re-enable hard end stops though.

I'm planning on moving my controller further away, and potentially placing it in a metal box. For the end stops however, I'm not sure how to solve it in an as DIY way as possible.

I've got a couple of questions:

1. How can I measure interference, and below what levels should I stay?
2. Will it help to simply wrap aluminum foil around my wires and hook that up to ground?
3. Does it work to hook up shielding to DC ground/zero, or should I hook it up to my AC ground in front of the AC/DC converter?
4. Where can I find a "beginners guide to magnetic interference"?

Answer 1

the CNC shield and the motor do not share a common ground,

This is one of your problems. A common ground and shield wires for all power and signals is necessary to minimize EMI. A small RF cap help on endStop switches only if you get false signals with NO switches wired correctly.

But avoid multiple SMPS if you can help it as users seem to not know why they have interference. I.e. use a laptop on battery with 1 supply for all CNC for starters.

Reading Henry Ott’s latest book or an older version in Archive.org will take you a few months to learn or longer but well worth it.

I would say shorter if your search skills found my answers here on this site.