Re: danger of unknown position after power down

[Paul <paul.corner-at-tesco.net>]

Hi Jacob

With stepper motors, I think the answer would be no. To get EMC to detect an 
amp fault (or loss of power to the stepper drives) would require the use of 
an input pin on the parallel port. The stg drivers have this ability via one 
of the inputs on the card. To extend this to work with the stepper driver 
wouldn't be too difficult.
Alternatively, a N.C. relay could be wired across the E-Stop switch and the 
coil energised by the stepper moter PSU. When the power cuts out, the relay 
will also drop out shorting the E-Stop. Whilst EMC will go in to E-Stop, the 
axis will still show green, so to force a homing will still require some 
coding.
A small extension to tkemc that automatically runs a homing sequence after 
E-Stop may be one way of doing it....


Regards, Paul.



On Sunday 13 January 2002 11:01 pm, Jacob Kranendonk wrote:

> If there has been a power failure or a power down on
> the machine steppermotors, can emc detect that? After
> power restoring the indicators stay green, even though
> the machine is obviously at an unknown position! I
> prefer even a obligatory axis homing before continuing
> the cutting after such a situation occurs. Is this
> possible? For instance I want the computer to stay
> "on" while the machine is turned "off" and I want to
> avoid people afterwards forgetting to home first. Or
> else, could the EMC be set up to automaticly home
> after each cutting job, to avoid this danger?
>
> regards, Jacob