Thanks for the math. I was going to try and figure that out.
The capacitors were a pain. I have to take this crystal off when my
replacement supervisor chip comes. I soldered up another crystal and
just wired the two capacitors across it. I think that will be easier
to solder to the three traces on the PCB.
I would still use the timer interrupt to set a real time value that is
used for program timing. I would hesitate to set the interrupts any
faster than 1 mS to have a reasonable balance between program and
interrupt processing. The Aux input can be set to edge-triggered
interrupts. I believe so can P6 and P7 on J3 with the same mechanism
although I never have tried it. It seems like you could wire the
slave PSIMs for edge interrupts to all monitor one of these signals as
a master clock and use this interrupt as the increment for the real
time value.
There are a couple of alternatives for clocking.
1. Have a master PSIM that simply clocks this line as part of the
timer interrupt routine. Accuracy is limited by the resonator.
2. Do the crystal mod on the master PSIM and clock to improve the
accuracy.
3. Have all the PSIMs be slaves and clock from some other more
accurate timing reference.
I'm still thinking about the tone burst ideas ...
Dave
--- In
ComputerVoltageSources@yahoogroups.com, Eric Brombaugh
<ebrombaugh@...> wrote:
>
>
> Nice soldering job - very tidy.
>
> I suppose that the real test of this modification
> would be how well two such systems track each other in
> real-time.
>
> Ceramic Resonators such as was originally mounted have
> +/- 0.5% accuracy. Crystal accuracy is typically
> +/-50ppm (100x better than the resonator), that means
> a worst-case error between 2 crystal oscillators of
> 100ppm. If you were using these to run a clock that
> equates to .36 seconds disagreement over an hour.
>
> To hit the 1ms accuracy that Gary quoted earlier you'd
> need to resynchronize such a system at least every 10
> seconds minimum. So, while using a crystal doesn't
> eliminate the synchronization problem, it
> significantly reduces the effort required to do so and
> still maintain reasonable accuracy.
>
> Eric
>
> --- djbrow54 <davebr@...> wrote:
>
> > Success! I had a tech at work take off the
> > resonator. I added the
> > capacitors (0302, I think) and a through-hole
> > crystal. Man were those
> > capacitors small! Rock solid performance! Photo
> > "AtomPro28 crystal.
> > jpg" is in the Files>BasicAtomPro>Original PSIM>Dave
> > Brown folder.