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Re: strange stopping
开云体育Electrical noise can be a bear.? Steve Spallings mentioned PC grounds and system or motor grounds.? I have his PMDX-126 and unfortunately the PC I'm using internally somewhere has the DC ground connected to the system frame which is the third earth prong on the power cord which then connects to the motor frames through the machine metal. The CUI encoders on the DC servos serve to further muck things up where their DC ground is connected to the frame.? Which is of course connected to the 3 prong and so DC ground earth ground are connected in several places. ?Shielding has no rhyme or reason here but it's one place where a single ended connection for a shield is a bit more logical. ? My EE book on electrical noise states that the signal grounds should never be connected to the DC power grounds or frame. ?The whole point of shielding is that it isolates the two. ? For your system also look at magnetic coupling.? The way a transformer works is a changing magnetic field introduces current in windings that are also in the magnetic field.? So the spindle motor current flowing through the wires can generate a field picked up encoder or limit switch wires. ?Short of what is called mu metal shielding the only solution to electromagnetic interference is distance.? Route them far apart. ? Electrostatic shielding is different.? Twisted pairs help to null out electric field noise. Shielding can be grounded at one end or both of the frame (third prong) earth.? The point is you only want the noise current flowing back through the shield into the frame.? Not through your signal wires which includes the DC 0V wires.? People tend to forget what goes out a signal wire is still a signal as it comes back through what is commonly called the ground or common wire.? (Some manufacturers have called the +5V to +24V 'common' for limit switches) ? John Dammeyer. ? From: [email protected] [mailto:[email protected]] On Behalf Of Todor Boshnakov
Sent: March-27-20 2:39 PM To: [email protected] Subject: Re: [MachCNC] strange stopping ? You are trying to fix a wrong schematic with cosmetic changes. You sure have a ground loop somewhere. Check your shields, they should be connected one side only with heavy short wire to good ground. Preferably star connection. On 27 Mar 2020, at 18:32, "spencer@..." <spencer@...> wrote:
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