[time-nuts] No more 60Hz, How do I discipline 120VAC 60Hz from a UPS
camaraq1 at quantacorp.com
Sat Jun 25 17:48:55 UTC 2011
Depending on your skills and amount of time you want to spend on this:
1. As you said, find a commercial UPS and just tie it to a time-nuts
grade 10MHz. I assume most modern UPS will be based on a $1 ARM or PIC
processor - if they run on external oscillator you can use a DDS chip to
generate the exact frequency they need to generate your 60.00000000 Hz. You
would need to find out the exact fractional relationship they use for this.
For instance, say a micro runs from a 25MHz oscillator, has an internal
10kHz interrupt that flips the output square wave every 83 counts. It
generates a 60.24Hz that was 'OK' for the original product. You would want
to feed it with 24.9MHz, derived from your good 10MHz via DDS. The risk is
that some UPS might just use micro's internal oscillator with no access.
2. If you want to go a little further (and possibly spend more money
in parts than a commercial UPS would cost you), you can use that DDS to
output 60Hz and drive the monster FETs directly (well some isolation / gate
driver required). Simplest is square wave, switch between sink/source to
+/- DC rails. Linear drive (like class B amp) to generate is inefficient.
Filtering square wave leads to large passives. Filtering stepped square
waves is a bit better, but switching between two rails with high frequency
PWM will generate a sine wave that is simpler to filter. Possibly you can
find some kit or schematics on the web, just replace the time base...
I'd get a good sinewave UPS (compare eBay, old, assume bad battery, compare
to new, Hong Kong) and add a REF-IN BNC to a DDS.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Don Mimlitch
Sent: Saturday, June 25, 2011 9:50 AM
To: time-nuts at febo.com
Subject: [time-nuts] No more 60Hz, How do I discipline 120VAC 60Hz from a
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)?
This would solve both my problem with power outages and the new problem
of possibly undisciplined power from the power companies (Henry Warren
must be rolling over in his grave!)
I have no Idea how you would disciple such a low frequency at such a high
deliver the power required to drive several (or many) Clocks.
I assume you would start with a commercially available UPS and either a
disciplined 1 Second
or 10Mhz source such as a thunderbolt (also powered off the UPS or the
batteries in the UPS).
Does anyone have an suggestions for circuits which would do this
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