On 2010-08-20, Pete C. wrote:

Ignoramus12820 wrote:

My mill was lacking something very important: the drives would remain
powered, and drifting due to test/offset, when EMC2 was not commanding
any motion.

Just to clarify: if EMC is holding position, then the drives are held
in position by EMC. But if EMC is not holding position, for example
because it stopped due to following error, then the drives would start
drifting.

It happened a couple of times already that I would forget about EMC
left without controlling position, and the mill would drift next day
to some unacceptable position and trip the limit.

I finally added an extra instruction to "inhibit" the drives when the
axes were not position controlled. Now, if EMC is stopped due to
following error, or I turned the motion off, the drives are inhibited
and would not do anything.

i

Do you have them inhibited if the watchdog timer expires due to a
software crash / hang?

If watchdog timer expires, the all output of Jon's PPMC shuts down,
and that turns off the main motive power contactor. There is no
problem with that.

I really should try to simulate a system crash while moving, for
example by pulling a power cord.

i