--- On Wed, 3/16/11, andy pugh <bodge...@gmail.com> wrote:
> From: andy pugh <bodge...@gmail.com>
> Subject: Re: [Emc-users] pwm AD converter
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Cc: "Klemen Dovrtel" <klemen_dovr...@yahoo.com>
> Date: Wednesday, March 16, 2011, 12:25 PM
> On 16 March 2011 08:38, Klemen
> Dovrtel <klemen_dovr...@yahoo.com>
> wrote:
>
> > I would like to measure some analog signals using emc
> (for PID control). I think the easiest way would be to
> measure the pwm signal.
>
> Measuring a PWM digitally is almost never the easiest way.
>
> > I was thinking i could use two oneshot functions, one
> to trigger on rising edge and one to trigger on falling
> edge. What i need is a function to measure the time between
> those two events - is there a hal function for that?
>
> I think you could use oneshot set to retriggerable and a
> sample-hold
> function looking at oneshot.0.time-left and triggered on
> the same
> pulse.
> Note that I said "could" and not "should". The main
> drawback is that
> the pwm duty cycle measurement will have a granularity
> related to your
> base-thread time.
>
> As Visteurs has been saying, voltage-to-frequency with an
> encoder
> module linked to the signal (in counter-mode) will give
> much better
> results, it is much less affected by the sample time
> granularity. You
> would use the encoder-velocity output as your analogue
> voltage value.
>
> Are you using a parallel port, or some other hardware?
>
> --
I understand it now... i haven't noticed the velocity output (it is not shown
on the block diagram). Will use that, thank you :)
Yes, i am using the parallel port. The frequency of AD measurement would be
approximately 10 Hz. Isn't this low enough to make a decent measurement?
Regards
Klemen
------------------------------------------------------------------------------
Colocation vs. Managed Hosting
A question and answer guide to determining the best fit
for your organization - today and in the future.
http://p.sf.net/sfu/internap-sfd2d
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
