RE: [CAD_CAM_EDM_DRO] Re: Pixie error connection

Yes I know that Tom.

But in this case we don't know what the OC driver is, and Skyco haven't
commented.

We also don't know what the pull up resistor is, it may simply be a
resistor, it could also be a processor OC output though most of these are
good for 10 to 20mA to drive LED's normally on the ground side only. We just
don't know how much juice we can pull from it.

The PCB is also a very tight SMT pcb with lots of tracks running under parts
and lots of thro holes under parts making it difficult to track to the right
device.



Regs Mark



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Tom Hubin
Sent: 15 July 2007 18:59
To: CAD_CAM_EDM_DRO@yahoogroups.com
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@earthlink. <mailto:thubin%40earthlink.net> net

**************************

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_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>

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,
>
>

[Non-text portions of this message have been removed]