Re: Pixie error connection

Mark,

I appreciate your input! I had envisioned the Pixie error circuit as
you described. I still don't understand why the error output would not
be sufficient to drive a DC solid state relay. When I connect the
error to the relay is just goes into an error state. There must be
something different about the open collector, which I don't
understand. Jim Cullins, who designed my breakout board has suggested
interfacing with an IC with Darlington arrays.

I have all the safeguards with limit switches etc. The system shuts
down everything during an estop coming from my servo amps or from
Mach3, the estop switch etc. However, the final protection is to get
the servo amps to shut off (signal the Mach3-Campbell estop)when the
Pixies fail. Now of course, the Pixies go into an error condition
without triggering an estop.

Thanks again,
Keith

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mark Vaughan" <mark@...> wrote:
>
> The pixie error output is am open collector output, and an input
with pull
> up resistors. What this means is each pixie card has a little transistor
> switch that switches the line to 0V when there is an error. When
there isn't
> an error the pull up resistor keeps the output at 5V, but being a
resistor
> it is low current. The idea is that you can wire all the pixie card
error
> wires together so which ever one faults pulls the line of all the
others to
> 0V which the others see as an input and stop themselves so when it goes
> wrong all pixie cards will stop so there will be no axis movement.
>
> As to interfacing to other systems, the output can only drive 5V logic,