old clocks - test-drb@ccmp.vtda.org

18 Oct 2011

Oh well, another post that reminds me of all that tinkering I'd like to do but
can't due to lack of time right now.

There is a broken Siemens "Hauptuhr" (master  clock) HU 10 in one of ?y banana
boxes from hell, which formerly did its duty in a school in my district. This is more
modern (I'd say 70s if not 80s vintage) unit with a lead-acid battery for backup and a
discrete electrical second (or maybe half-second) oscillator driving the
"seconds" part of the mechanical work, which in turn actuates a contact to
generate "minute" pulses for both the minutes/hours hands of the local dial and
the slave clocks. It seems that just the primary oscillator or maybe the seconds actuator
is broken, as manually generating pulses via the Set button does advance the hands as
expected.
What's more, the device also comprises a loop of, IIRC, 5-level punched tape in a box
with, I think, one "character" position for every five minutes in either 24
hours or even seven days, which would usually probably be used to ring a bell for
signalling the breaks at the desired times (on schooldays), but could of course also
accomodate other functions.

I also do have a kind of slave clock, but not the usual hands-and-dial variety - mine is a
digital one which looks like it was from some kind of larger office and works by means of
plastic sheets printed with numbers and arranged in a horizontal drum, which flip
downward, one per minute, at the actuation of a magnet. Besides hours and minutes, this
thing also has a whole calendar with day-of-week, day-of-month and month display derived
from this movement, but I've not yet investigated how it deals with the different
lengths of the months, i.e. whether it will need manual intervention every two months or
just once a year (apart from going into/leaving DST, of course).
Unfortunately some greedy, egoistic creature has pilfered some of the flip sheets, so
these will have to be recreated using some kind of plastic stock and painted to match the
figure patterns of the rest.
Uh huh, how long will I have to live...

So long, yours sincerely

Arno Kletzander
...sent from HTC Magician PDA

----- Urspr?ngliche Nachricht -----
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 Message: 17
Date: Sun, 16 Oct 2011 18:39:08 +0100 (BST)
From: ard at p850ug1.demon.co.uk (Tony Duell)
To: cctalk at classiccmp.org
Subject: Re: old clocks
Message-ID: <m1RFUg7-000J43C at p850ug1>
Content-Type: text/plain
  Does anyone in here admire/collect old clocks?  I
want to get a Standard  
Hell yes. I've been interested in clocks for longer than I've been 
interested in computers  :-). All types of 'clocks' actually, from 
sundials to atomic clocks.

I am (as you have probably guesed) more interested in the movements 
(mechanisms, working parts, call it what you will) than the cases. 
Unforutnately, antique clocks are expensive, so I can't own what I'd 
really like to own, but I cvna still enjoy repairing a 1930's shelf clock 
that I've bought for \pounds 10.00 or so in a charity shop (thrift 
store). 

  Electric AR-2 slave clock (60s style).  I fondly
remember that model as 
 the one used at my elementary and junior high schools. 
Alas I cna't help you there.

-tony

Message: 19
Date: Sun, 16 Oct 2011 19:22:58 +0100 (BST)
From: ard at p850ug1.demon.co.uk (Tony Duell)
To: cctalk at classiccmp.org
Subject: Re: old clocks
Message-ID: <m1RFVMX-000J48C at p850ug1>
Content-Type: text/plain

  I was a proffesional clockmaker for a while.
 We did mechanical, electric and electronic clock repair and
 manufacture, till the site closed.
 Dont forget you will need some form of master clock to drive the slave dial.
 The drive is a current pulse set to a fixed current and all the dials
 are in series. 

Many slave clock systems had the dials in series as you describe (and as 
is described in Hope-Jones's book), but I am sure the system we had at 
school (which weas almost certainly from Gents of Leicester) had the 
slave dials in parallel and fed them 24V pulses. I deducdd the first fact 
by unpluging the connector on one of the slaved and finding it had no 
effect on any of the others and the latter by useing a 'scope...

Anyway, the pulses for that system were alternate polarity pulses, one 
pulse per minute. Something like this : 

   --                  --  
  |  |                |  |
--   ------    ------    ------    --
           |  |                |  |
            --                  --

  |        |
  |        |
   <-1min->

The slave clock motor was similar in concept to the motors in those quartz
insert movements. It had 2 mechncially stable positions half a turn apart.
The +ve goign pulse pulled the (magnetised rotor) one way round between
the ends of the coil core, when the pulse ended, the rotor moved ot the
nearest mechanically stable position. The next pulse (of the oppostie
polarity) again lined the rotor up with the coil core, but the other way 
round, It then moved to the other stable position. And so on.

The master clock had a spring-drivien mechancial movement with a short 
(about 30cm) pendulum. The spring was automatically rewound my an 
electric motor, and would keep the clock running for quite a time (12 
hours or more) if the mains failed. The pulses to the slave dials were 
generated by a pair of 3-terminal mercury switches, which were rocked by 
a camshaft. Power to the switches (and thus the slave dials) came from a 
transofmer/rectifier unit. Of course if the mains failed, no pulses were 
gneerated (there was no battery backup) and the slave dials didn't move. 
However therew was a mechanism invovling a mains motor and a differneital 
gear which kept track of the missing pulses (when the mains motor wasn't 
turnign). When the mains came back on, the thing 'caught up' generating 
pulses every few seconds to reset the slaves to the correct time,

Anyway....

While it would be nice to have such a master clock (or, indeed one of the 
synchonomes), these slave dials (in all the common systems) effectively 
count electrical pulses. And it doesn't matter how you genrate the 
pulses. Provided you know what the pulses should look like (voltage, 
current, whether they have to be of alternating polarity), it's a fund 
exercise to design a digital circuti to produce them using your favourite 
technology, whether that's TTL, FPGAs or microcontrollers.

-tony

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