(See more details in the next log)
So I received the central piece of the quartz clock : the quartz !
A box arrived from Ukraine, the seller described the contents like this:
"Russian/USSR made Quartz Crystal Resonators 18 KHz. Crystals are in mint condition never soldered. Each crystal is in individual manufacturer's packing box with individual OTK certificate. Manufactured in 1989 Purchased from a storage of electronics manufacturer which is no more in business. "
Why choose these ? Well, there is no need of a socket (which would cost more than the tubes), the price is good (but increasing), 18KHz is not hard to work with (I found interesting dividers) and the look is awesome. A higher frequency means a smaller crystal, which would be less visually interesting and requires more flip-flops to divide down to 1Hz.
The plan is to
- divide by 8 (3 chained toggle cells)
- divide by 15 (4-bits toggle ripple counter, with AND4 to detect number 15 (all 1s))
- divide by 15 again
- Divide by 10 with a Johnson counter (with fancy LEDs to show the 10s of seconds)
Total : 11 toggle (divide by 2) and 5 DFF (16 modules)
23 more FF are needed for the remaining stages, seconds, minutes and hours (5+3+5+3+5+2) [does anybody need a day-of-week indicator ?]
Total: 39 FF modules.
I have NO IDEA what that thing was used for. Why is 18KHz used ?
And I have no clue about the driving method because there are 3 active signals and not two, which is the norm I'm used to.
But let's start by opening the box:
Can it be more Russian ? :-)
Each little box contains one glass tube and a "passport", a small sheet that describes the part:
I'm sure that this last picture contains very interesting informations, about operating temperature and accuracy... But I can't make sense of them yet. Anyway, the date code is obviously 29 dec. 1988 (though Russia uses the Julian calendar, shifted by 13 days compared to the gregorian calendar we use in Europe, so yes, that's 1989 for "us").
The tubes themselves are great, though I have many questions about their design and use...
(click to enlarge)
There are 3 electrodes, one at the back (next picture), two at the front, and one is 1/3 of the length only.
The above picture shows that 2 electrodes support the crystal at the exact opposite of the others. The distances are carefully chosen to reduce interference or dampen the oscillations...
I suppose that the crystal resonates in the bending mode, like a vibraphone plate. However I don't know how to drive it, what is the excitation electrode and the sensing electrode.
I suppose that the excitation is applied through the single electrode on one side, and the small electrode on the other, leaving 2/3 of the surface for sensing/collecting the charges. This structure does not correspond to the stamped logo on the passport, which describes a more classic structure with excitation on two opposite sides, and collection between the perpendicular electrodes.
I have noticed that the quartz bar is not square, but slightly rectangular...
That's all I can say for now. Stay tuned ;-)