RE: [CAD_CAM_EDM_DRO] DC brush type motor control

Hi Les

Common mode noise on the motor lines is well within acceptable limits, you
probably had a low inductance motor with a lot of winding to ground
capacitance.

My motors are 8.1mH and motor generated noise has not been the big issue.

On my drives all the noise came back down the encoder output wires that
leave the card, Rutex have not buffered these, they provide the main on
board signal, and a connection to the outside world. They cross talk like
hell with the step/direction and other SPI input signals.

I had solved all the noise problems when one decided last week to go tipsy,
no noise on the encoders lines right up to their processor, I have captured
all the encoder signals during the move on a 450MHz long memory dso, they
are nice and clean, yet when it should be driving the motor in one direction
it seems to keep sporadically mixing forward moves with backwards jerks, and
runs up short on position, the processor isn't seeing what it is being sent.
It could be just bad probability, but !!

When they work the PID control is good, but they really need help with the
EMC and other issues, and I am running short on time to keep playing with
someone elses prototype design that is sold as a completed design. If the
designer would work with us that's a different issue, but he cannot be
bothered to reply to anyone, leaving his US distributor Tom to try and pick
up the pieces and quite often the bill. I know the designer has had personal
problems, but this has to change if they want to survive.



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Leslie Newell
Sent: 03 April 2007 19:18
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] DC brush type motor control



A common mode choke makes a big difference to noise on Rutex drives. Get
a chunky ferrite toroid and wind the two output wires around it about 6
or 7 times. Keep it as close to the drives as possible. I had huge noise
problems on my lathe until I did that.

I think the Rutex drives switch a bit too fast - great for power
consumption but very bad for noise.

Les

Mark Vaughan wrote:

>
> Many of us have Rutex drives. Some like them, some have endless noise
> issues. The PID control is good, but transient protection and noise

immunity

> appears not to be.
>
> I have Rutex drives, I have beat the noise issues, but after a recent
> failure am looking for a more reliable drive.
>

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