Help please. Dip switches and mach 3 settings

[cropwell]

Hi,

Having typed a long and laborious answer to some of your points, I then lost it all because this forum software is crap.

Here we go again :-----

1. a: Pigtailing - no problem, just remember shields should only be earthed at one end or you may get earth currents to make your shield as the primary in a transformer with the secondaries as your signal wires.

1. b: Single earth point in control box, all earths and shields and mains earth to it. Topographically, earth connections are a star, however spur connection is allowed as long as it is a single line spur chain earthed at one end only at the star point.



2. Yes.

3. The VFD is usually the main culprit in creating electrical noise and it is common practice to keep it out of the main enclosure (which should be an earthed, shielded box I.E. not plastic).

4. DC voltage supply lines are normally no problem in a steady state, switching transients can be a nuisance, but these would only be when there is an inductive load, like a pump motor, so these are best shielded. Homes and limit switches are normally in a steady state, but it wouldn't hurt to shield them against stray EM crap.

5 and 6 - whatever !

7. I hate ferrites and their nasty little cousins - slugs. Design out the problem if you can.

8. Noise from the BoB, not usually (only when it gets drunk on a Saturday night) but seriously - I refer you back to 3 above.

You should test each earth connection by continuity checking from the central earth point to the earthed appliance. Disconnect the appliance earth and check that the continuity between the earth point and the appliance then disappears. If it doesn't - you had a loop.

Hope this helps !