RE: [CAD_CAM_EDM_DRO] Pixie error connection

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,
skyco do not provide enough information to lead us to believe it can drive
anything else. Normally one would take the signal back to the breakout board
to a logic input that is used to trigger the software into reset so it stops
sending commands. It is not normally considered necessary to Estop the
system since all axis will stop, only the spindle is left operational, the
machine should be in a safe position from where an operator can recover it.



On my machine presently being installed with pixies, I will wire the three
errors together, and back to one of my G100 inputs to signal a fault in
Mach3. I have limit switches wired to my analogue cards, and also to mach so
both are triggered should a limit be hit, but again no Estop, my analogue
cards are nice since if they are on a limit, movement in that direction is
stopped. I have a second set of limit switches that pull the Estop out,
which cuts power to the spindle, and all power to my analogue cards
including the HV supply, this is the last resort if a serious electrical
malfunction occurs. My pixie cards also drive an enable to my analogue cards
which pushes the analogue cards into a maximum current/deceleration stop
should a fault occur. This same analogue enable line has a switch on it that
is used to halt the servo's under this condition for my cards it is safe to
put ones hands in, it also halts mach operation so no movement commands are
sent which could error fault the system. I think that's most of it.



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: 14 July 2007 23:37
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Pixie error connection



Has anyone used the Pixie 100 board that can help me figure out how to
connect the error line to my breakout board. I was unable to get a DC
in/DC out solid state relay to work like I expected. The error line
is held internally high at 5v until there is an error, then it goes
low. I thought that it should work by connecting to the control side
of the relay then with an error it would open the switch on the output
side to signal the estop of my Campbell break out board. All it did
was signal an error condition on the Pixie until I disconnected the
error line from the relay. The error line in an in and out line so
that driving it low from externally will also signal an error. Jim
Cullins has recommended a ULN2803 chip to interface but I can't get
one for a few days.

Thanks
Keith Clark





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