Do you use EMI filters and/or ferrites in your controller cabinet? What works?

06 Dec 2022 19:36 #258730 by Sray69
I am learning about filters and ferrites before I build my controller cabinet so that I can implement them during the build. But I need some help with the following questions. 

  1. Which type of ferrite do I use? Ni-Zn or Mn-Zn?
  2. What frequency range ferrite do I use?
  3. What wires/cables do I put the ferrites on?
  4. Best location for EMI line filter?
Currently I am planning to put a EMI filter on the input lines for each of my PSU's. I am planning on putting ferrites on each step/dir wire. Not sure yet which type/frequency though. I am thinking about using shielded cables for the cables that leave the cabinet (motor cables, limit cables, etc) since those cables will be quite long and ferrites are not as effective on longer runs. 

I know a lot of people say I don't need to worry about EMI in my build, especially since I am not running a inverter/spindle yet. But I would rather include some cheap/easy EMI/RFI reduction methods up front instead of tracking them down and having to redo things later. Plus I do plan on upgrading components later which will most likely add more noise/interference.

What has worked for you? What hasn't?


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08 Dec 2022 22:48 #258923 by andypugh
I would always recommend putting inout filters on a VFD, but I have not seen the need for general PSUs driving GPIO or relays or similar.
There _might_ be an argument for filtering the power to the stepper supplies, as those have a fairly notchy current demand.

I generally search on eBay for "Rasmi" and find one rated for the correct voltage and current.
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