Re: [CAD_CAM_EDM_DRO] ServoToGo opto isolation

emserv@... wrote:

> Hi,
> Iam almost ready to connect the STG card into the amps,encoders,etc.
> on my Matchmaker mill.The STG hardware manual states that the board
> is OPTO-22 compatible , but Iam not sure which I/O`s need isolation
> and how to go about it,any information would be greatly appreciated.

I haven't connected much digital I/O from the STG to anything. Part of
the reason
is that the standard programs for EMC do almost all the auxilliary
functions on a
parallel port, and use the STG's digital I/O mostly for limit switches.
See
http://ascc.artsci.wustl.edu/~jmelson/schem.html for some ideas on
limit
switch connection, and http://ascc.artsci.wustl.edu/~jmelson/schem.html

to see how I wired my auxilliary stuff up. I have it set up so if there
is an
external E-stop, amplifier fault or watchdog timeout, the auxilliary
stuff
will be shut off, completely by hardware, even is the computer is hung.

Isolation on the limit switches is not a bad idea, but if installed
properly,
it is pretty unlikely that line voltage could get into the limit switch
circuits. If it ever did, however, the entire computer would probably
be reduced to charred rubble! So, if there is some possibility that
a runaway saw blade could cut through all the wiring, you could save
a big mess with isolation.

Obviously, if a control output line needs to turn on 110 V to the servo
amps, or something like that, isolation is needed by a relay of some
sort.

Jon