You are right. Synchronizing the PSIMs will not improve the accuracy,
it will only make all track together. If the overall accuracy is not
good enough, an external clock would be a good solution. However, the
error might be fairly constant. In my clock program, for example, I
can correct it by adjusting the timer to ~1 mS by measuring the
frequency externally and changing the divisors. You might be able to
do something similar with a correction factor if error is constant.
Another option is to replace the resonator on the AtomPro. I have
replace the power-on reset chip on my AtomPro28. You'd have to find a
crystal with the right dimensions and have a steady hand ...
Dave
--- In
ComputerVoltageSources@yahoogroups.com, "Gary Chang" <gchang@.
..> wrote:
>
> Dave,
>
> First off, thanks for the analysis - indeed, the phasing of the
three
> PSIMs seems to coincide with the 5% error spec that you list in your
note.
>
> Dave, when you finally get down to it (syncing your two PSIMs, that
> is), please consider just creating an external sync clock input, so
> that each of the PSIMs will run from a common external clock - there
> is no need to provide a way for a 'master' PSIM to slave another
PSIM,
> since the master clock is not accurate enough to be useful!
>
> A simple clock input, with supporting code to specify what the PSIM
is
> hearing (240 ppm, 96 ppm, 24 ppm, etc.) would be useful.
>
>
> Gary
>
>
>
>
> "djbrow54" <davebr@> wrote:
> >
> > The data sheet for the AtomPro24 specifies a 16 MHz resonator, not
a
> > crystal. Resonators are about 0.5% accurate, vs. a crystal that
is
> > measured in ppm. At .5% accuracy, after 60 seconds your PSIMs
could
> > be off by 300 mS, or as much as 600 mS if one was +.5% and one was
-.
> > 5%. I always thought that they had crystals, but when I wrote my
> > clock program, I noticed that it gained or lost time after minutes
and
> > hours. A crystal should be better than this so I think they are
> > resonators.
> >
> > I would synchronize the PSIMs. I'm not sure what Aux is doing
since
> > inputs and outputs are not documented in the code. Perhaps one
PSIM
> > could 'watch' the other Aux output to synchronize. There would be
a
> > little latency but this could be accommodated by adding
appropriate
> > delay in the master PSIM.
> >
> > I personally would use my MIDI for synchronization as a background
> > communication channel. I would simply send a status byte from one
> > PSIM to the other to keep then synchronized or perhaps to even
send a
> > timestamp value. I've always been a proponent of MIDI on the
PSIM,
> > even if you aren't using MIDI, as a way of expanding capability.
I
> > think John Loffink has some of the display/MIDI expansion boards
still
> > available and have been just amazed that PSIM owners haven't
snapped
> > them up.
> >
> > I'd comment more on how to synchronize this program, but don't
have
> > the patience to figure out inputs, outputs, and functionality in
> > generally undocumented code.
> >
> > When I get my second module going, I'll probably look into how to
> > synchronize programs. In general, I'd probably use a timer as a
real-
> > time reference. I generally run it at 1 mS interrupts. It would
be
> > easy to generate an event on a binary value, such as on the 256th
> > count, or so, in the interupt routine to pulse Aux. On the other
> > PSIM, I'd setup Aux as an edge trigger as use the interrupt to
> > synchronize the real time reference to the nearest 256 timer
count.
> > All outputs would be referenced to this real time reference, and
not
> > pause commands. Seems very doable.
> >
> > Dave
> >
> >
> > --- In ComputerVoltageSources@yahoogroups.com, "Gary Chang"
<gchang@
> > ..> wrote:
> > >
> > > Being one of very few that has more than one of the PSIM-1
module, I
> > > did a little test to evaluate the relative timing accuracy of
the
> > > PSIM'S internal clock, by loading the maf-lfo2.bas application
into
> > > each of three modules and starting them with a common start
pulse.
> > >
> > > The test results can be heard in an mp3 called PSIM mayhem,
found in
> > > the files folder of this group.
> > >
> > > So - it looks as if we are going to need an external sync
reference
> > to
> > > get these guys to be time reliable. Probably a simple pilot
tone
> > > (such as a vco) would be the easiest to reference....
> > >
> > > GC
> > >
> >
>