[time-nuts] Pendulum Clock Synchronization
Brooke Clarke
brooke at pacific.net
Thu Mar 5 17:55:42 UTC 2009
Hi:
The Western Union clocks made by the Self Winding Clock Co. have a provision
for hourly synchronization of the hour, minute and second hands using a pulse.
Since there were many thousands of these in service they are constantly on
eBay. See:
http://www.prc68.com/I/SWCC.shtml#Sync
http://www.prc68.com/I/SWCC2.shtml#SC
When they were used in government buildings, banks, jewelry stores, etc. the
line voltage was 120 VDC and the current was adjusted to 250 ma with a variable
resistor. Note that the time constant of an LR circuit is proportional to L/R
so raising the voltage allows adding resistance speeding up the circuit. This
is mandatory in teletype circuits and makes a big improvement in the operation
of the synchronizing circuit for a clock or operation of a slave clock.
Since it's only one pulse per hour I've started looking into using a free power
supply that runs on a single AA cell. The problem with these is that the
voltage is about 300 VDC, but that may be OK if current limited to 250 ma (abut
1200 Ohms). See:
http://www.prc68.com/I/LED.shtml#SUCFBO
--
Have Fun,
Brooke Clarke
http://www.prc68.com
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