Max, this is going to be an awesome project - one where I think everybody will get the juxtaposition of old and new tech.
I still think that making it "dead on" accurate using a GPS time source would be pretty cool - "I'll just sync my pocket watch with atomic clocks orbiting the earth, using my steam-punk analogue meter clock".
Maybe make the seconds tick inconsistently, but have it bang-on when the seconds hand goes from full scale back to zero.
Neat project! I've lived more in the digital realm than the analog, so I'm curious how you're planning to drive these meters. Do you have the voltage and current specs for each? I imagine they'll require more power than a microcontroller output could provide so I'll have to stay tuned for the next report to learn how you plan to do that.
How about doing the whole thing analog? Each meter can be driven from a timebase like an oscilloscope or analog computer. You can sync between them the same way the horizontal and vertical waveforms are synced in an analog TV, but with more stages. And then sync the whole thing to 50/60 Hz line frequency to keep accurate time.
Yeah, parabolic. A-T is third-order. For both, cut angles can select the curve parms, making the field wonderfully complicated. I used to have a booklet from Fox with some details, but can't find it; things like using crystals in series to get compensation, DC bias effects, good stuff.
@ GSKrasle Could you build a PLL with the relay cycling as input, and take a multiplied output frequency?
Imagine how many hours that would take to lock. You have a VCO generating about a 1sec output that gets knocked down to 1 minute pulses to be compared to the signal from the relay. The phase error is then used to adjust the VCO frequency until the error is really small. You'd need lots of 1 minute pulses for the loop to do it's thing and sync the VCO to the relay.
Hamfest site is hamvention.org. Dates for 2015 are May 15-17. We are at the Quality Inn Suites. On Maxton Rd, is a solid mile of hotels and restaurants near the airport and convention center. Currently reserved for Fri-Sun but could modify easily. Joe and his wife (same schedule as us for now) likely not interested in the tour as they have been going since before they rename the Hamvention!
Another interesting property of the 32K tuning forks: their frequency vs. temperature curve is a parabols, with the peak right at 37C! Your wrist is the oven..... also explains why a (properly trimmed) watch will lose time when off your wrist.
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