RE: Request for comment - G320 wiring

>
> Subject: RE: Request for comment - G320 wiring
>
> I looked at your schematic and have one comment - E-Stop switches are
> normally hardwired into the system, and should not require that any
> electronics be functional. As drawn, your system has the potential of
> failing in the "run" position if the electronics fails. This would not meet
> OSHA safety requirements. If the Geckos are like the Camtronics, you don't
> want to suddenly open the lines to the motors, but you probably want to
> interrupt the power supply to them with a switch contact. Once you have this
> hard-wired override, then you can run additional signals to the PIC (or to
> the computer) to inform your control of what has happened.

I agree to having had second thoughts about the EStop inputs as well.

I've used PICs in NASTY environments and they've always come up smelling like
roses. Note that the electronics would have to fail in a particular and
unusual manner for things to fail "on".

OTOH, there may not be as nasty a place as a shop floor. And Murphy does lie
in wait for the proud. So I guess I'll rethink this bit.

Here's another question or two for you then, if I may.

1. Is it permissable to power the relays through an EStop switch and still
be considered "safe". I would REALLY like to avoid having all the motor
current going through the EStop switch.

2. Is there any point, short of laziness/convenience, in having separate
XYZ limit switches ? It would seem to me that the OR of the limit switches
would equal an ESTOP .. or do machines usually have an extra set of switches
set just "outside" the limit switches to act as ESTOP sensors ?

Thanks for the thoughts.

Alan



--

Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta