[time-nuts] No more 60Hz, How do I discipline 120VAC 60Hz from a UPS

Chris Albertson albertson.chris at gmail.com
Sat Jun 25 17:25:34 UTC 2011

On Sat, Jun 25, 2011 at 9:50 AM, Don Mimlitch <donmeis at yahoo.com> wrote:
> I collect clocks an have many clocks with 60Hz Synchronous Motors.
> How would I go about Disciplining a 60Hz 120VAC source from an
> Unintteruptable Power Supply (UPS)?

Most comercial UPS are quite crude.  Theu make square wave AC.  In
your case, I think the way to go is to build a precision 60 Hz
oscillator .   It can be very low power and work at 5 volts.   I would
deriv the 60Hz from a 10Mhz reference, either devide it down then
drive a PLL or use a DDS chip.    Filer it then usethis precission
60Hz signal to feed something that looks a lot like an audio
amplifier.   This kind of design is expensive if you need many watts
but you clocks likely don't need many watts.

The amplified can run from a high voltage DC source.  As (I assume) we
don't care about efficiency you can drive the amp with a 200V DC
linear supply like you'd find in a tube based amp.   the feedback loop
of the typical audio amp is replaced be an an AC voltage comparator.
Feed back drive the output to exactly 120V.

Use a different design if you care about power consumption and waste
heat.  The above is a simple "on line" supply.   A comerical UPS like
this is more complex and uses a SMPS for the high voltage and runs the
SMPS from a battery that is also being charged from AC mains.   These
use a crystal for a freq. reference.   You might just buy one and
replace the crystal with a DDS drive from your 10Mhz reference.  But
these comercial on-line units are not cheap like home computer backups


Chris Albertson
Redondo Beach, California

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