1. #1
    Do EMI power line filters serve any purpose in a DIY control circuit, or should I ask is it worth including one at the mains inlet. I'm getting mixed responses.

  2. #2
    Hi Jim,

    I included one between the mains and VFD unit (plus a ferrite coil around the spindle cable) and have had absolutely no problem with interference from the spindle over several years of operation, the radio reception is crystal clear (digital if that make a difference), and there are no complaints of electrical noise issues inside the house when it is running.

    Unfortunately I have never run it without so don't know if it is definitely required - but I don't remember paying much for it and would do it again just to ensure no issues.
    Last edited by routercnc; 13-03-2014 at 09:06 PM. Reason: typo
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. Yes is the short answer...

    Without it I had real issues with noise on the mains affecting answerphones, tv (admittedly analogue tv) and Ethernet.

  4. #4
    Thanks for your responses, but what is a ferrite coil. I'll google it but you may be able to explain in simple terms that I will understand.

  5. Basically a ring of ferrite. You wind a few turns of your cable onto it and it acts as a high frequency choke. For smaller cables you can also use a ferrite bead which you slip over the cable or a ferrite clamp which is like a large split bead for thicker cables. All of these can help but a good EMI filter is best.

  6. The Following User Says Thank You to irving2008 For This Useful Post:

  7. #6

    As Irving has described I clipped one of these types of ferrites on each end of the spindle cable just in case:

    12 5mm Clip ON Ferrite Core Data Cable Ferrous Ring Bead Choke Filter EMI RFI | eBay

    Here's my VFD (top right), mains filter (bottom right), and brake resistor (middle) which was a waste of money (50) as I never used it since the spindle stops pretty quickly without it.
    Click image for larger version. 

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    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  8. #7
    Quote Originally Posted by GTJim View Post
    Thanks for your responses, but what is a ferrite coil
    Jim, I
    t's not a coil, it's a Ferrite Core,

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