Re: E-Stop Revisited

Hi Peter,
For a system that is not tightly-coupled hardware/software, (and a
desktop PC running Mach1 is not), I do not suggest a simple "soft-
stop". Especially since Mach1 is running on top of Windows. You
can't expect Mach1 to be able to handle a real "E-STOP" situation
given the platofrm it has to work with.
Remember, simply cutting AC power can leave a large amount of
power left in supply caps, which could power steppers longer than you
want in an "emergency" situation. Better to cut the DC power to the
stepper drive itself. This means a big relay/contactor capable of
handling the DC current to the drive.
What might be an alternative, would be a 'real' E-STOP button which
would be used to cut power as mentioned above, then also a big
red "FEED-HOLD" button that would be feed into MACH1 (though not the
same shape as the E-STOP button: there should only be ONE E-STOP
button). Upon getting the "FEED-HOLD" at it's "E-STOP" input, Mach1
could stop motion as best as it can. At high speeds, if Mach1 just
stopped sending pulses, you could still end up loosing steps though.
The "feed-hold" button could handle those cases where a slow move
crash could be avoided. It would be easier to hit the "feed-hold"
button than using a mouse/screen based STOP button, or picking out
the right key on the keyboard, to stop motion.
Well, that' my opinion anyway.

Jeff
http://www.xylotex.com

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Peter Cruickshank
<crankshaft_sg@y...>" <crankshaft_sg@y...> wrote:

> Hi;
>
> Ok, what's the conclusion on the E-Stop issue, should the big red
> button cut power to everything, or is s soft-stop good enough !
>
> I know that there are different opinons on this, but for the

general

> hme hobyist CNCer with a Sherline 5410, What's the recommendation ?
>
> Cheers
>
> PeterC