[time-nuts] Mechanical 1PPS Oscillator Disciplining

Jim Lux jimlux at earthlink.net
Sat Jan 10 19:44:42 EST 2015

On 1/10/15 3:08 PM, Hal Murray wrote:
> holrum at hotmail.com said:
>> Basically the solenoid nudged the pendulum
> There was an article in Scientific American many years ago.  They used a
> magnet mounted on the end of a stick attached to the pendulum arm.  The arc
> of the magnet swung through a hole in the middle of a solenoid coil.  A pulse
> on the coil at the right time provided the nudge with no physical contact.
or a coil under the pendulum bob, which is ferrous, a technique used in 
some large Foucault pendulums

I didn't realize you can actually buy them as a sort of catalog item..


They put the drive at the top.

The most fascinating thing is the list of 122 pendulums they've installed
and some of the places they are.. there's a goodly number of museums, of 
course, but some other things..Wineries, Banks, Malls?

the one in the Smithsonian was removed some years ago..

Very simple design
the schematic (and the user manual including tuning instructions) is on 
the website under "manuals"

Just a photodetector driving a solenoid, which apparently draws 300 mA 
from a 120VAC line.

I haven't found details on the coil or armature design, but plenty of 

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