[time-nuts] Mains Frequency

[Hal Murray]

artgodwin at gmail.com said:
> Andy, what equipment do you use to monitor the cycle count ? 

I use a modem control signal connected to a serial port on a PC.

Most OSes have code to grab a time stamp on an interrupt.  The target usage 
was a PPS signal for timing.  It works OK at 60 Hz as well as 1 Hz.

http://users.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz.py


> I wouldn't be surprised to find that streetlight clocks use the same old
> Sangamo or Venner electromechanical timers that they've always used, and are
> far more of a problem to correct than domestic clocks. 

Most streetlights in the US use photocells.  (The switch was being made 50+ 
years ago, when my father was selling the sockets that the lights and 
photocells plugged into.)

You can often see them if you are off to the side.  There is a bump on top of 
the light, roughly 10 cm in diameter and 10 cm high.

-------

Off topic:

The main motivation for going to photocells was to avoid the cost of separate 
wiring for street lights.

In the old days, the street lights in front of my house were run in series, 
like Christmas tree lights.   There was only one clock and one meter for each 
string.  But you had to run separate wires to each street light.  The lights 
were actually on separate poles.  (They were cast iron rather than wood.)

When they started using photocells, they mounted the lights on utility poles 
and just connected them to the handy wires.  There was a photocell someplace 
connected to a meter.  The billing system just multiplied by the number of 
street lights.

The socket for the old series lights was an interesting setup.  There were 2 
parts.  The lamp screwed into a removable socket that had 2 big blades 
sticking out the bottom.  They were spring loaded to touch each other.  You 
put a piece of paper in between.  The blades poked into another socket.  I 
assume the contacts in there were setup to short out if you removed the lamp 
socket.

When a lamp burned out, the high voltage powering the whole string would make 
quick work of the paper spacer and the rest of the lights would glow a little 
brighter.

I never got a story about what happens when too many lights on a string burn 
out.  I assume there was a fuse in the box with the meter and clock.

Andy said radio so maybe there has been another transition since my youth.



-- 
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