EMI Filters, any purpose in a diy control circuit?

[irving2008]

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.

[routercnc]

Jim,

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.