Inductive Limit Switch problem

[cropwell]

Embarrassing but I must own up: I realised during my tests that for all these years I've left the 36V supply for my stepper motors floating. Neither rail was grounded so the whole supply was bouncing up and down by 8 Volts at several KHz. It's a miracle the machine worked at all! Any way that's now fixed and some of the bits from RS have arrived, though not the screened cable for re-wiring the sensors yet.
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I am just rewiring my control panel and realised that my 48V to the drivers was also floating.

[Kitwn]

Muzzer, Neale,

My original issue with this was in regard to noise getting into the BoB supply which appeared to have been a major part of my problems. It seemed obvious at the time, but I take the points you both make. As long as the BoB supply and the motor supply are completely separated and the cable screens effectively grounded it should not be an issue. I have my machine working now and am keen to start using it to make things but I thing the next time I decide on a significant upgrade it will have to include a complete rebuild of a new controller in a better enclosure with a far more comprehensive approach to noise screening.

The clamp-on ferrites look like an excelent idea and I'll order a bagful.

Rob,
As you'll see from the above replies, you shouldn't be changing that anytime soon. My reasoning lacked the rigourous engineering logic it should have had.