Quartz Kitchen Clock Movement

© Brooke Clarke 2007

Quartz Kitchen Clock
          Movement



Background

I have an idea for an improved clock and wanted to see how they are now made.  One side of the crystal has a trace that has 4 solder bridges which must terminate in capacitors on the IC under the epoxy blob.  Most likely in a binary weighting.  In the manufacturing process the free running frequency of the mechanism could be measured with a counter and then using a look up table the operator puts solder bridges on the proper pads.  In my case from top to bottom it's closed, closed, open, closed.

The impedance of watch crystals is extremely high so you can not probe the crystal circuit to measure the actual oscillation frequency.  What was done here is to use a pair of pogp probes to measure the coil drive pulse per second.  The length of that time interval should be exactly one second.

Drive

A positive pulse of 1.37 volts lasting 46 ms is followed 1 second later with a negative pulse of 1.37 volts lasting 46 ms.  This means that the IC uses a full H bridge circuit in order to get the bi polar drive from a single 1.5 volt AA cell.

Marking

On back of clock: Spartus, Quartz, Made in U.S.A.
On printed CCircuit Board: 239/1-1,  Spartus, 57 11103 90

Disassembly

In order to use the movement when driven from a more precise time base than the on board crystal this movement was removed from an old kitchen clock.  This was done by prying the clear cover tabs and pushing so the clear cover could be removed.  Then the tabs paper dial and hands were removed.  Finally the movement was pushed out the front after the tabs on the frame were held back.

Spartus Quartz Clock
          Movement out of boxA number of plastic hooks hold the mechanism into the movement box.  All but one of these can be seen and with a small screwdriver pried enough to lift the mechanism up a little.  But the one under the printed circuit board seemed impossible to get to, so I cut a hole in the box.  Here a bottom view.  Note that three gears and a flat spring dropped off and have been reassembled for this photo.

The small white plastic circle at the 10 o'clock position of the leftmost gear is the armature.





Spartus Quartz Clock
          some gears removed




Here the three loose gears have been taken back out to show the metal magnetic path and the armature.  The armature is made from a permanent magnet, but I don't yet understand how it works.







Patents

2457637 ELECTRICAL MOTOR, Harrison D. Brailsford, Dec 28 1948, 310/46 ; 310/40MM; 310/40R - self starting (offset magnetics) pulsing clock drive motor, very low power
Fig 4 shows the structure
References:
362322 ELECTRIC MOTOR, EOBEET J. SHBBHY, May 3, 1887, 310/46 - 4 coil looks like start stop stock ticker drive
1367982 MOTOR, QTTSTAVE Lidseen, Feb 8, 1921, - AC/DC armature has teeth instead of windings
2185990 INDUCTION MOTOR, self starting
2214850 SELF-STARTING SYNCHRONOUS MOTOR, GE 1939 - uses permanent magnet for rotor
References:
1497394  Alternating Current Motor, Henry E. Warren (Warren Clock Co), Jun 10 1924, 310/163 ; 310/126 - self starting AC synchronous
3969642 Step motor for electronic timepiece

Links

Low Power Time-base -

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