On Thursday 30 January 2014 18:08:38 andy pugh did opine:

> On 30 January 2014 22:23, Dave Cole <[email protected]> wrote:
> > The hint is: "pot control with external 5 volt control available"
> 
> However, it might still work. LinuxCNC can output speed-dir if needed.

This is what I am doing for the spindle of my small lathe.  I had to synth 
the stop signal in hal because g33.1 doesn't stop, but goes direct from fwd 
to reverse & back.  Effectively issuing a stop when the dir changes, and 
doing a stop until the encoder says its the same as stopped, then clocking 
the new direction signal on thru.

Because the driver is a 25 amp driver, while the motors circuit breaker is 
9 amps, the stop is made into a full stop by zeroing the commanded speed 
all the way through the command chain, so the restart in the opposite 
direction actually starts from a stopped condition and is subject to the 
accel limits in the command path.

Complex but it was doable.  But I have encountered a bug when the G33.1 
(rigid tap) is used in a loop doing a peck cycle.  If the loop repeats too 
many times, the spindle and Z will disconnect when z is max left.  At the 
same time the disconnect and resync at the right end of the Z travel, may 
or may not disconnect.  So there is a stray sign, or unsigned as the case 
may be, var internal to the G33.1 that can bite you if you try to tap too 
many turns deep.  It hasn't broken any taps for me, yet, but in cutting air 
4" from the chuck and observing it in an air cut run, I have seen, and 
heard it occur a goodly number of times.

IOW here, its fairly repeatable.

Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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