ComputerVoltageSources

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
>