RE: [CAD_CAM_EDM_DRO] Re: Pixie error connection

Hi Kieth

No problem helping, we all bat things between each other here, that way we
all learn.

When the pixies fail they release the enable line to your analogue cards, so
if you trust the pixie logic that should adequately shut off all movement,
in reality tripping with an error should be a very rare event, on my machine
it might occur if I hit a limit which freezes mach and my analogue card, if
mach freezes quick enough even this shouldn't trip the pixie. If you have
additional Estop limits after your main limits then you are covered should
a card fail and motor go wild, I've had this happen with Rutex cards. If I
were to wire the pixie error into the Estops, so much power is pulled that
no led's would be left active to tell me how the fault occurred.

As to your solid state relay, it is probably just too much load, so the
relay itself pulls the inputs all too low and they trip into fault mode.

If we knew what they are using on the pixie card for their open collector
output then we might be able to add a little more resistor pull up so it
could drive the relay. I haven't any boards at hand at the moment to have a
look, but the tracks aren't easy to track so even then we might have a
problem. I would just put a transistor on the output, something like an
MPSA13 darlington transistor and use that to drive a relay.

I have emailed Rick at Skyco for details about the error lines, and enable
output lines that feed the analogue cards, but didn't get a response



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 toolspindoctor
Sent: 15 July 2007 16:43
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] 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_ <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,

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