Re: [CAD_CAM_EDM_DRO] Re: EMC problem/question

currinh@... wrote:

> This makes too much sense. :-) I built a small opto-isolation board
> which goes between the computer and driver boards. Thinking through
> this circuit I figure it IS inverting the signals. SO, I pulled it out
> and tried another test. The directions, both X and Y, reversed so the
> opto-isolation does invert the signals (easily changed in the *.ini).
> And with the isolation circuit taken out no off-set occured, dead on.
> PROBLEM SOLVED, or at least isolated. :-)

OK, well what you need to do is un-invert the step pulse. You can add
one more inversion to get it to step on the proper transition from the
computer.

>
> I'd like to put the isolation circuit back in so I may work on the
> problem more. Seems like a simple do nothing loop at the right place
> in EMC would do the trick. The problem is where to put it. :-(

No, I don't think so. If you invert the way the step pulses work, that should
do it. (Ie. put out a zero where it used to put out a 1 and vise versa.)
Then, you would have to reinsert this patch every time you updated the
EMC software. It might be easier to put an inverter chip in the isolation
board.

>
> > If this doesn't seem to be the problem, you should try steppermod (if you are
> > using freqmod) or vice versa.
> >
> I tried to run freqmod but it wouldn't function. EMC fires up but the
> motors don't move (just buzz as if getting pulses too fast). What
> parameters are configured in *.ini besides "freqmod.o"? I briefly
> looked at linuxcnc and nist but didn't find the info right off. Can
> you, or anyone, direct me to a description? This could be a better fix
> than patching steppermod and no doubt more useful to know.

Others have answered this, set output_scale the same as input_scale.
And, put period back in. You need to set a reasonable interrupt interval
for this parameter, somewhere between 16 uS (0.000016) and 40 uS
(0.00004) seem to be numbers people have had success with.

Jon