First...some info on the Hipp Toggle.
Everyone knows that is you set something swinging, it will slowly decline in amplitude and stop. In the case of a clock pendulum the decline is affected by three interferences.
1) the suspension on which it hangs. This is usually a spring
Matthias Hipp's original Hipp toggle was a simple metal toggle attached the the side of the pendulum rod that closed a contact when the arc of swing fell to a certain minimum amplitude. It then momentarily powered an electro magnet as the Pendulum passed through "zero" or bottom dead centre. This impulse accelerated the pendulum slightly on that swing. The arc increased and the Hipp toggle effect would not be invoked again until the arc had again fallen to the set amplitude.
The clever bit is that the pendulum is subjected to the minimum of mechanical
interference over significant time intervals - often 30 seconds or more.
Matthias Hipp proposed this idea in 1842. Below is Frank Hope-Jones description of the Hipp toggle. It's reproduced from his 1949 book "Electrical Timekeeping". Frank Hope-Jones was the designer and manufacturer of the 20th century Synchronome master clocks (which did not utilise the Hipp toggle)
The Hipp Toggle principal was not widely used but the British Post Office used it in their telephone exchange master clocks until as late as 1980. There is a good explanation of the Hipp Toggle Post Office No. 36 clock at http://www.hvtesla.com/masters/po36_toggle.html . If necessary have a look ; It may help understand what follows.
I had wanted to make a pendulum clock of my own
for a long time. It was always going to be largely electronic because
my mechanical skills are not too good. My inspiration
came from the master clocks with one second pendulums that were so popular
in large buildings during the first three quarters of the 20th century.
The Synchronome clock designed by Frank Hope-Jones being one of the
best. I have a few other clocks HERE
I am not a proper horologist, so my "bible"has been the book referred to above. I have tried to abide by the important priciples outlined by HJ in that book. There are other electrically maintained pendulum clock ideas to be found on the internet and no claim is made that this scheme is any better than the others. It is just an interesting experiment in basic electronics and horology.
My "toggle" effect is produced with opto-interupters, rather than mechanical devices. These have an infra-red beam passing between two small pillars, which, when broken by a passing object, output a pulse for as long as the beam is broken. The type I have used have a comparator chip on a small pcb and were sourced cheaply from eBay. (as low as 99p)
A short length of soft sleeving which I will call the "flag" is attached to the 4ba rating thread beneath the bob so that it passed between the the pillars of three opto-interupters as the pendulum swings back and forth, creating the operating pulses as it passes. Soft plastic sleeving is used to prevent damage if the flag accidentally hits the arms of the opto-interupter.
The optos are arranged from right to left in the order A, B, C. When the pendulum is stationary the flag hangs midway between optos A and B - ie. at Bottom Dead Centre (BDC). An important point is that the electro magnets are co-incident with opto A; slightly to the right of BDC.
When the clock is running, as the pendulum swings from its rightmost extremity, it first passes through opto A, then B generating a short pulse from each one as it goes. A and B and C are all 0.5" apart A and B are centralised on BDC.
Opto C is the Hipp Toggle sensor. It works like this. Assume the pendulum has sufficient amplitude to swing right through opto C at its leftward extremity. A pulse is generated. It then stops and begins to swing back to the right. It passes through C again, generating a second pulse.
So on every swing that has sufficient amplitude
to pass through opto C twice, two pulses are generated in quick succession.
These are fed to a cmos flipflopr chip (CD4013, a) which is wired to
divide by two. In other words, the output of the 4013 ff is clocked
HIGH then LOW.
All the while the pendulum arc is slowly decreasing and eventualy there will come a time when the flag does not pass right through opto C, but enters it, reverses, and proceeds to the right again generating only ONE pulse. This will clock the counter HIGH and and it will remain HIGH as returns to the right. This is the equivalent of the mechanical toggle catching on the V block in a mechanical Hipp Toggle clock.
As the pendulum continues its swing back to the
right it arrives at opto B (1/4" from BDC) generating another pulse.
A basic chip known as a NAND GATE (IC3a, CD4011) detects that it
now has two HIGH signals on its input terminals - one from opto
C which was left in the HIGH state and a HIGH from opto B as the flag
arrives. With these two HIGHs on its input its ouput goes LOW, is inverted
in IC3b to make a HIGH which triggers a flip flop (IC2b) to HIGH.
Thus the HIGH on THIS FF (ic2b), which lasts as the pendulum travels fromn opto B to A, is the drive period control for the electro magnet's drive pulse. This drive pulse is switched on with a transistor and the Electro-Magnets are powered during that section of the arc (B>A) giving the pendulum an impulse which maintains the pendulum in motion.
On the next swing the pendulum will again pass right through opto C because of the slightly increased amplitude and the process will repeat in as many seconds as the energy given by drive pulse will allow. (It's about 50 seconds in my clock)
A feature of this design is that the pendulum arc is closely controlled by the position of opto C relative to BDC. ie. .75" This works out to be about 1.9 degrees or 0.95 semi arc. This is quite a small arc which is good for time-keeping and the system has been so reliable that an even smaller arc might be entirely possible.
Here's a short video showing the pendulum as it was in an earlier trial period when the "flag" was in front of the bob. The LED on Opto C can be seen to blink twice until, after about 30 seconds, it only blinks once (circled). A drive pulse is generated as described above. Please note that sometimes the quickest of the double blinks appear a single blink due to the frame rate of the video. Positioning the flag at the front of the bob was not a good idea and in the final design it is concentric with the bob.
The purpose of Ic1 (6x Schmidt trigger inverters) is to speed up the pulse edge transitions from the opto-isolators. Used in pairs,the original pulse polarity is maintained.
The completed electronic cHipp Toggle unit
We now have a drive pulse positioned 1/4" either side of BDC which, when amplified by the transistor switch, powers the EMs for 220 milliseconds; that period being set by the distance between opto A and B.
Frank Hope Jones in the Synchronome clock, powered his pendulum at fixed 30 sec intervals with the potential energy of a gravity lever hanging up on a catch so that the energy imparted as the bob passes through BDC was always the same.
The pendulum impulse in this clock is delivered magnetically to the armature beneath the bob. The force of attraction of a magnet varies as an inverse square law of the decreasing distance to the approaching armature.
In this clock, the energy that pulses the EMs
does not come directly from the battery, but from a capacitor charged
to precisely 5 volts from a voltage regulator. This ensures that exactly
the same energy is available on every impulse. The capacitor value was
found by trial and error to empty its charge during the 220 millisecond
period that the drive is energised. Because of the capacitor the current
through the EMs decreases exponentially over the 220 millisecond drive
The oscilloscope image below shows the falling voltage applied across the drive coils during the 220 milliseconds pendulum drive period. A side effect of this system is there is virtually no back EMF generated when the swicthing period ends, so protection of the switching transistor is not needed.
Due to inductance, the current waveform is slightly different..In particular it has a slower rise.
The armature beneath the pendulum is of low remnance steel taken from a GPO relay. There are no fixed magnets in this design. (and no auxilliary timing circuits)
Here is the circuit diagram of this "capacitor
How it works. The Qbar output of ic2b in the Hipp toggle circuit , which is normally HIGH, is connected to the input (i/p) on the left. This turns on 2n3906 transistor which in turn turns on the 2n5193 pnp transistor above. TThe 3300uf capacitor is charged quickly to 5 volts exactly . The 5 volts comes from the 2940-5 low drop out voltage regulator (2940-5).
When the cHipp Toggle circuit calls for a pendulum impulse, Q of ic2b turns on the EM's drive transistor (lower right), At the same instant Qbar goes low , removing the 5 volt feed to the 3300uf capacitor. The capacitor is now the only source of current for the EMs during the drive pulse period. (220 Milliseconds)
* the 16ohm and 33ohm resistors in the electro-magnet circuit were adjusted to achieve a time between impulses of about 30 seconds. Later the period was changed to over 50 seconds.
The cHipp Toggle clock has no friction other than that of the suspension spring and the air through which it passes. It has a very small arc which is tightly controlled so circular error has virtually no impact. The is no escapement to interfere with the motion of the pendulum except for the precisely controlled impulse which are now every 50 seconds. Temperature stability is achieved with an Invar rod although there may be an issue with the bottom supported bob expanding upwards. Therefore I am tempted to believe that an electrically impulsed clock of this type might be as good a pendulum clock as can be constructed whilst running in free air. Only the often mentioned quartz rod pendulum rods might offer a small improvement.
It was Frank Hope-Jones's Synchronome clock system (and his previously mentioned book) that inspired me to make this clock. One of the advantages of the Synchronome system is that the current consumption of a Synchronome clock is miniscule whereas any electronic clock has a continuous drain. Of course, in a modern quartz clock this drain is reduced to a tiny current but the cHipp toggle clock is drawing 90 Ma continuously because of the three opto-isolators, LEDS indicators and the electronics.
This is not much of a problem as I've used a trickle charged 6 volt lead acid battery in case of a power cut.
I have made a start on a second clock. This will use the case of a PO No36 clock and the chassis of an "ME Jubilee electric clock" I've no idea yet what principles will be employed
I have also bought two more Synchronomes one of which ( a late MK2) has two BO22439-3 printed circuit boards which send alternate polarity drives for half minute and one second dials. Work is in progress to trace out the circuit diagram. These boards must be rare as their is no published information on the internet - or a mention in the Synchronome bible by Miles. Please email me if you have any info on these boards.
Originally the clock was fitted with a Synchronome dial mechanism that required an impulse every 30 seconds. This was taken from opto B and a simple divider circuit included to make the impulse every 30 seconds. This has now been didpensed with and it's now fitted with the Gents, silent, seconds indicating, alternate polarity slave clock mechanism mentioned in the introduction. The dial motor resistance is 3.4 ohms and the required drive current is 220Ma. The dial was printed on silver card with a laser printer.
Pulses from optos A and B are "or'd" and inverted in ic3d (circuit above) and fed to the circuit below.
The incoming double pulse is converted to a single pulse of about 220 milliseconds duration with a period of one second by 4013a (ic3a). This is divided by 2 in 4013b. The two opposite phase (Q & Qbar) phase outputs are gated with the single pulse to produce positive going pulses of 220 milliseconds duration alternately, to drive the H-bridge. It was just luck that the spacing of Optos A & B were 220 Milliseconds apart and that the pulse resulting at 4013b i/p was a suitable length to drive the Gents dial movement.
The gem in this circuit is the tiny H-Bridge module sourced from ebay for a mere 99p post paid. Rated up to 10 volts and 1.5 amps its more than adequate to drive the dial motor. Pictured above with a £1 coin for scale, it features two H-bridges, so a couple of additional series dials could be run separately from the B output.
The steady current consumption is now 100ma - mostly due to the LEDs in the Opto-interupters and the other indicators.
How well does it work ?
The clock is capable of keeping extremely good time. The
temperature compensation is not perfect and has not been adjusted on
test. There are still short lengths of brass (top suspension) and steel
(suspension spring, 1.5 inches steel making up the shortfall of the
1 metre Invar rod and the 4 Ba rating thread) which could be compensatated
for in some way. The bob expands upwards and will compensate to some
extent to the downward expansion of the parts listed above - albeit
at different rates due to their mass.
In the initial trials I found some variations in rate
which were difficult to explain and the following mechanical improvements
The constrction of the clock has been an on/off process over several years. During that time I've been lucky enough to make the aquaintance (online) of a chap who has written a program for the RaspberryPi (mini computer) that can monitor and record the going of a clock in remarkable detail. Originally designed for the Synchronome system it accepts and records the timing of the 30 second pulses against internet time (NTP) I've used the divide by 30 board which formed part of my clock in its first configuration to feed the Pi monitoring system.
The cHipp clock has been sadly ignored for the last year but here is an update..The clock is capable of keeping good time but occasionally behaves badly..This update is triggered because of an event yesterday which is typical and totally not understood. The graph from the computer logging below shows a day and a half of near perfect running...but at 21.00 on the 13th Sept yesterday as I write) there was an abrupt change of phase and the clock immediatly began to gain at about 1 sec.per day. I was out of the house at the time. I must find the cause of this problem but don't really know where to start looking !
Vertical red lines are "days" Horiontal dotted lines are 1 sec apart.
last updated 13/09/18
Another update. 20/11/18
The cause of the event shown above was never found. While the clock was stopped and the pendulum stripped down, a device was fitted that I hoped would provide better temperature compensation. This is shown below.
A weight attached to the top of a copper rod whish is itself fixed by a bracket to the pendulum rod. By moving this device up or down the rod the amount of temperature correction can (should !) be adjusted..At the top, as shown here slowing of rate is at a minimum when the temperature rises..The jury is out at the moment as to how well this is working.
Update..It seems to overcompensate and the top chrome plated weightwas removed..I can be impatient when it comes to detailed observations and in Dec.2018, before reaching any conclusion, I added a small heating element inside the case with a thermostat having a 0.1 degree differential. The case is lined with12mm polystyrene and a sheet of acrylic plastic provides a degree of double-glazing.
The temperature has stayed very close to 22.d C for several weeks and I believe the remaining variations in timekeeping are caused by barometric pressure changes.
Unfortuately the Pi monitoring system is away for repair at the moment and no graphs are available.
Update Jan 20th 2019
I mentioned a while ago that I intended building another
clock - and thought it might be based on the unfinished ME Jubilee clock
I have. Change of plan !
So, with his help, I have made a start on cHipp Mk2. First I have to make a case. Some work was done last year on an ex GPO36 clock case for which I've already made a door. The chassis, pendulum assembly and drive magnets will all be PO36. Details and Pics to follow....
This scheme could be added to an existing PO36 clock withoutpermanently damaging or modifying it..
what is sound mixing