RE: [CAD_CAM_EDM_DRO] Re: breakout boards plus - hard choice

You may be right Jon, but I thought Mariss's break through was being able to
detect the load problem before loosing steps without an encoder.

Really if he's done it with an encoder that's a pretty simple task and not
worthy of all the hype.



Regs Mark



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 Jon Elson
Sent: 19 July 2007 18:08
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: breakout boards plus - hard choice



Mark Vaughan wrote:

> It may be possible to do this with a Grex, but that would require encoder
> feedback to the Grex, which is not part of the unstallable stepper
> philosophy.
>

I believe it HAS to have encoders to detect the phase angle
between the coil currents and the mechanical position. I am
very sure Mariss described having an encoder on the motor whiole
doing his experiments. Although it may be possible to detect
this phase angle from the voltage/.current pattern of the
motor's coils, I think it would be extremely difficult to do it
over a wide range of speeds, and practically impossible to do at
zero speed.

> The unstallable stepper just relies that if there is too much load

How can the drive know what the load is, except by the motor
being pushed away from the commanded position?

Jon





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