Re: [CAD_CAM_EDM_DRO] Re: Pixie error connection

----- Original Message -----
From: "Tom Hubin" <thubin@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, July 15, 2007 1:59 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Pixie error connection


> Hello Mark,
>
> Open collector outputs will sometimes drive a relay. One end of the
> relay coil goes to the open collector output and the other end of the
> coil goes to +5v...not to ground. The open collector can sink current
> but sources nothing. The pullup resistor, if it is there, is the source
> for +5v and that is rarely enough to drive a relay coil, although may be
> enough to drive a solid state relay.
>
> Try to find out what the open collector device is and the max current
> that it can sink when the output is low. Then use a relay coil or solid
> state relay that requires less than that. Just be sure that the relay
> input that is not tied to the open collector is tied to +5v.
>
> Sometimes you can tie it to +12v instead of +5v but that requires more
> info to decide.
>
> Tom Hubin
> thubin@...
>
> **************************
>
> toolspindoctor wrote:
> >
> > 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,
> >
> >
>
>
>
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