RE: [CAD_CAM_EDM_DRO] home switches

Hi,

The technique I use on my TurboTaig board is to combine the home switch
input with the 'home' (phase 0) signal from the stepper driver. I checked
the datasheet for the 5804 and it doesn't have this output. The 3977 or the
ST L297 does though. This output on these components is there to solve
exactly your problem.

The processing consists of only activating the home switch input to the
computer if the home switch and the stepper driver outputs the home signal.

This provides better repeatability as there is a positional error in the
location at which the home switch activates. With the processing above, when
the home switch is activated, the stepper will continue stepping into the
switch until it gets to it's phase 0, position.

For a 1/2 stepper system, this is a maximum of 7 steps. If you have a 1/2
step drive, a 200step/rev motor, and a 20tpi screw, 7 steps is 0.000875"
(7 * (1/(200 * 2 *20))

Mariss, is the Vampire likely to have a home output?

Cheers,



Peter Homann
mailto:Peter.Homann@...
Adacel Technologies Limited,
250 Bay St, BRIGHTON, 3186, AUSTRALIA
http://www.adacel.com <http://www.adacel.com>
Telephone +61 (3) 8530 7777, Facsimile +61 (3) 9596 2960
Mobile 0421-601 665

> -----Original Message-----
> From: david_margrave [mailto:david_margrave@...]
> Sent: Wednesday, 24 March 2004 12:32 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] home switches
>
>
>
> Hi
>
> I'm a bit confused about the whole concept of home switches. How do
> you get any degree of accuracy and repeatablity based on mechanical
> contact of a switch closing? What sort of things have people done
> for this? Just wondering because I'm at the stage in my micro mill
> CNC project where all I have remaining is wiring up the
> home/limit/stop switches. The stop switch was easy - just connected
> the switch to the output-enable pins of the allegro-micro 5804 (maybe
> some pull-up resistors were used to, I forget exactly). I am using
> EMC on linux.
>
> cnc project page http://www.margrave.com/static/cnc/
>
> Dave
>
>
>
>
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