How to safely turn off the computer while the motion servo is still enabled?

[jihuang]

When we use PCI-7344 and set it for serve closed control, I have found a very serious problem
in using the control card in this mode.

As the card is able to control motors only with the computer at power on status, but if we are very
carelessly to shut down the computer and without the notice to turn off motor driver power first
we would always get serious sudden moves of the motors, and might cause damages to the system. The same situation also applies to when control the motors under open/closed loop stepper mode.

How should I do to prevent the above situation?

(note: in my system, we have hook up relays and timers if we could set DIO bits before shut down
the computer. But
still, there are a certain occassions that the operator would still forget to set the DIO bits
and turn off the computer directly)

[algames]

The Inhibit output pin of the motion controller (also called drive enable) is the best way to achieve this. It is basically a signal that most power drives take in as an active low input so that when the powergoes out of the computer, the line goes low and immediately kills the axis so that no servo ouptut command affects the motor.

Best regards,

Alex Games

[jihuang]

Dear Alex:

Thanks for your reply. I guess that we have used the wrong polarity of inhibit output. Your suggestion is apparently a good lesson to me.

Jih-Jenn