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Gents impulse clock

How does it work

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Plasma13/06/2019 09:00:06
337 forum posts
41 photos

Hello all,

I have a Gents pul-syn-etic impulse clock unit from an old college.

Obviously it is not a stand alone unit and requires a master unit to drive it.

What does the master unit look like and is it possible to get this thing running using a more modern drive system?

Just wondered if it was possible.

Best regards Mick

Speedy Builder513/06/2019 09:07:05
1820 forum posts
128 photos

Search "Gents" on this site perhaps ?

SillyOldDuffer13/06/2019 09:38:17
4719 forum posts
1010 photos

Good description of the Master Clock on this web-site. If I read it right the master sends a pulse once every 30 seconds to a 4Ω solenoid in the slave(s). I'd use an Arduino and a Real-Time Clock module to produce a pulse every 30 seconds. If you don't require accuracy, an Arduino on it's own is will work the clock with moderately poor timekeeping. Also needed a 9V DC power supply and a transistor switch to drive the clock, also available as a module. That would allow a slave to keep good time after manually setting the hands. If you fancy having a go, I'll knock up a circuit and the simple software.

A synchronised clock expert will probably know, but the original system may have used other pulses to automatically set the hands of the slave clock to match the master. Watching a demented modern slave clock in my doctors waiting room, it was sent a signal setting it to 12:00 followed by a rapid series of minute pulses that wound the hands to actual time. Unfortunately after 30 seconds the master repeated the whole procedure, it was sicker than I was! Mechanical clocks probably do similar, but I expect the details vary by system.

Dave

Plasma13/06/2019 10:02:39
337 forum posts
41 photos

I was a bit too targeted in my search, looking for impulse clock which gave no results.

It came from the lady Mabel college which was based at Wentworth woodhouse. I was asking what the master might look like as there is a long cased clock with a pendulum just sitting on the floor in a corridor and I wondered if that was the master.

I'm rubbish at any kind of electronics but it would be nice to make the thing run again. Looks like all the others were stripped out and have gone.

I'll have a look at the bigger clock and report back if they appear linked.

Best regards Mick

SillyOldDuffer13/06/2019 10:22:38
4719 forum posts
1010 photos

Ah, with you Mick. A look inside should reveal all. The coils, wiring, absence of gears and mechanical construction are very different from an ordinary clock.

The website above won't let me link to their image, but they have a photo of the insides of the master.

Dave

Edited By SillyOldDuffer on 13/06/2019 10:24:22

peak413/06/2019 10:42:52
avatar
852 forum posts
71 photos

I would certainly grab the long case clock before anyone skips or damages it.
Examine carefully before you move it as there may be a lift off pivot for the pendulum. My own ex-GPO one has a set of brackets internally for supporting the pendulum rod for transport, with the cast iron weight being carried separately.

Obviously measure lengths before detaching the weight. My own one(s) were designed for 50v working, but mine have been fine running off 12v for 20 years.

Any chance of some photos please?

Bill

Alistair Robertson 113/06/2019 10:44:41
59 forum posts
6 photos

A factory where I worked for a couple of years about 15 years ago had a Gents master slave system with about 30 slaves at least. Even the stamping in and time jobbing clocks were linked.

When a new digital swipe card system was introduced the guys who installed it couldn't believe that a system that was at least 60 years old could do almost as much as their fancy system with all the bells and whistles!

The master was a long case clock as described by Mick so I think you have found what you need.

duncan webster13/06/2019 11:25:39
avatar
2232 forum posts
32 photos
Posted by SillyOldDuffer on 13/06/2019 09:38:17:

Good description of the Master Clock on this web-site. If I read it right the master sends a pulse once every 30 seconds to a 4Ω solenoid in the slave(s). I'd use an Arduino and a Real-Time Clock module to produce a pulse every 30 seconds. If you don't require accuracy, an Arduino on it's own is will work the clock with moderately poor timekeeping. Also needed a 9V DC power supply and a transistor switch to drive the clock, also available as a module. That would allow a slave to keep good time after manually setting the hands. If you fancy having a go, I'll knock up a circuit and the simple software.

A synchronised clock expert will probably know, but the original system may have used other pulses to automatically set the hands of the slave clock to match the master. Watching a demented modern slave clock in my doctors waiting room, it was sent a signal setting it to 12:00 followed by a rapid series of minute pulses that wound the hands to actual time. Unfortunately after 30 seconds the master repeated the whole procedure, it was sicker than I was! Mechanical clocks probably do similar, but I expect the details vary by system.

Dave

 

I've done exactly what SOD suggests using a PIC, I'd now use an Arduinos. Rather than an RTC I used the electronics out of a quartz clock to generate 1 second pulses (I got the clock for nowt!), the Arduino counts to 30 then sends a pulse via a transistor to the Gents mechanism. Take up SOD's offer, or do it yourself as a learning exercise.

If you've got plenty of money you can just buy a complete unit.

The original Gents/Synchronome masters just sent a 30 second pulse round all the slaves. if a slave managed to miss a beat it had to be manually corrected. What SOD is referring to is akin to a 'waiting train' movement where the local clock ran under its own steam , but ever so slightly fast, when it got to the hour it waited until it for a pulse before setting off again. At least that's my understanding. There were other mechanical systems where the local clock was set to run ever so slightly slow, and every hour a pulse was sent which physically pushed the minute hand to 12

Edited By duncan webster on 13/06/2019 11:27:14

Guy Lamb13/06/2019 12:17:30
64 forum posts

Just be careful typing 'Gents impulses' into Google you never know what might come up!

Guy

Peter Bell13/06/2019 14:56:05
275 forum posts
134 photos

LOts of slave dials around and I would certainly be interested in seeing an Arduino use an RTC (I have a ZS-042) to generate 30 sec pulses for a slave and if possible display the time on a 1.8TFT display (I have a ST7735B)

I am probably ok with the electronics but perhaps SOD could do a mini series like he did for the CAD?

Seems so sad to see these slaves "quartzed" and lost for ever!

Thanks Peter

SillyOldDuffer13/06/2019 15:38:42
4719 forum posts
1010 photos
Posted by Peter Bell on 13/06/2019 14:56:05:

...

I am probably ok with the electronics but perhaps SOD could do a mini series like he did for the CAD?

...

Thanks Peter

OK, watch this space.

I don't have a ST7735B Display, so that bit might be a wild guess! It's a graphical output. I'll show how to use the Arduino environment to set the RTC and then how it to make it produce 30 sec pulses. I can display hh:mm:ss to the monitor window to prove the RTC's working, or to an ordinary 1602 LCD without much trouble.

Dave

Bazyle13/06/2019 16:16:05
avatar
4727 forum posts
186 photos

SOD having mentioned the inaccuracy of a free running mocroprocessor to make it more interesting for you as a programmer how about adding a push button that the owner presses at precisely midday then the arduino knows its error accumulated since the last button press, however many days, and knows how to correct the counters. Another button for telling it when daylight saving occurs.

Michael Gilligan13/06/2019 16:24:05
avatar
14020 forum posts
608 photos
Posted by Peter Bell on 13/06/2019 14:56:05:

LOts of slave dials around and I would certainly be interested in seeing an Arduino use an RTC (I have a ZS-042) to generate 30 sec pulses for a slave and if possible display the time on a 1.8TFT display (I have a ST7735B)

I am probably ok with the electronics but perhaps SOD could do a mini series like he did for the CAD?

Seems so sad to see these slaves "quartzed" and lost for ever!

Thanks Peter

.

I totally agree, Peter ...

But I must just add that the really clever/important part of these systems was the Master Clock, and of course its use to keep a circuit of Slave Dials in synchronisation.

Attractive as they may be: The slave mechanism is nothing more than a basic electromechanical indicator.

MichaelG.

Edited By Michael Gilligan on 13/06/2019 16:27:38

Frances IoM13/06/2019 16:24:11
643 forum posts
24 photos
why not just extract the mechanism from a radio controlled clock or even the many GPS rcvrs that push out the time accurate to microseconds!
Michael Gilligan13/06/2019 16:51:09
avatar
14020 forum posts
608 photos
Posted by Frances IoM on 13/06/2019 16:24:11:
why not just extract the mechanism from a radio controlled clock or even the many GPS rcvrs that push out the time accurate to microseconds!

.

Which reminds me of a round tuit ... I have most of the parts to build something like this:

**LINK**

http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm

MichaelG.

Peter Bell13/06/2019 17:05:07
275 forum posts
134 photos

Dave, Thanks.

Yes a 16x2 lcd will be fine, once its showing on the serial monitor I can manage. Arduino seem good on displays and I found I2C works well. Its just that the TFT displays are so cheap I bought one!

Peter

SillyOldDuffer14/06/2019 15:10:56
4719 forum posts
1010 photos

PART 1

PURPOSE

To imitate a Gents pul-syn-etic Master Clock to drive a compatible Slave Clock, or clocks.

REQUIREMENT

  1. An accurate timekeeper that maintains time even when the device is switched off
  2. User allowed to set the clock accurately
  3. Clock to display time (and date)
  4. Device to output a tick (pulse) at hh:mm:00 and hh:mm:30
  5. Pulse to be able to switch a substantial voltage and current
  6. Simple Mains Power Supply
  7. As plug and play as possible. (Minimal or no soldering, using common low cost components)
  8. Free, simplified development environment for the Microcontoller.

HARDWARE

  1. The accurate Clock is a Real Time Clock Module based on the DS3231. The chip is a precision temperature compensated timekeeper commonly used by personal computers to keep time when the machine is switched off. They can be bought as a ready to use module from Amazon, ebay, and most electronic suppliers.
  2. As the Arduino microcontroller comes with a serial interface and can communicate with a laptop computer via a USB cable, time can be set by any computer with terminal access to the serial port. A package like putty, Hyperterminal etc.
  3. The display is a Arduino 1602 LCD module. Two types are available, this project uses the cheaper version, not with an I2C interface.
  4. A Microcontroller can be programmed to work the Real Time Clock, output 'Ticks', and run the display. I used an Arduino Nano, which requires some soldering The code will also work on an Arduino Uno, which has socket headers.
  5. As the output of a microcontroller is weedy it is used to drive a Relay Module; these are rated to 10A at 250Vac. The Slave Clock and it's power supply would be connected to the relay contacts, and thereby electrically isolated from the Arduino and other delicate electronics
  6. A Mains to 5V USB charger like this Wall Wart example.
  7. Constructed from modules as described above, connected by soldering, or Prototyping Jumper Wires & a Breadboard. (Make sure to get a good selection of Male to Male, Female to Female and Male to Female jumpers.)
  8. The Arduino IDE is free, well documented and may be downloaded to run on Windows, Linux or Apple computers. It is also possible to develop code online with a Browser. (Not tested this myself!) Libraries are available for all the modules used in this project: they remove most of the 'heavy lifting'.

CIRCUIT DIAGRAM

rtccircuit.jpg

In real life, as implemented as a prototype lash-up for testing:

dsc06121.jpg

It would be possible to neaten up considerably by plugging modules directly into the prototype board. For a permanent solution, I would solder to Veroboard.

More later...

Dave

Edited By SillyOldDuffer on 14/06/2019 15:12:53

Michael Gilligan14/06/2019 15:23:08
avatar
14020 forum posts
608 photos

Brilliant work, Dave

MichaelG.

SillyOldDuffer14/06/2019 15:40:41
4719 forum posts
1010 photos

rtccode1.jpg

rtccode2.jpg

rtccode3.jpg

rtc_code4.jpg

rtccode5.jpg

rtc_code5.jpg

rtc_code6.jpg

The source code may be downloaded from Dropbox.

SillyOldDuffer14/06/2019 16:13:08
4719 forum posts
1010 photos

PART 3

Installing the Arduino IDE should also all install the libraries apart from that needed to control the DS3213 real time clock.

The DS3213 library should be downloaded from www.arduinolibraries.info/libraries/ds3231 and installed using the Arduino IDE.

Start the IDE by double-clicking the icon on the desktop. (Light Blue, with Infinity sign in white)

Go to the 'Sketch' tab and click on 'Include Libraries', then select 'Add .ZIP Library'. Navigate to your Downloads folder and select 'DS3231-1.0.2.zip'.

To compile the program (aka 'Sketch' , plug the Nano into the PC with a USB cable. Then go to the 'Tools' tab and click on 'Boards'. From the list select 'Arduino Nano'.

Then go to the 'Tools' tab and click on 'Ports'. From the list select the /dev/ttyUSBnn or COM device identifying the Nano.

Clicking the Right Arrow button, top left of window, should compile and load the program into the Arduino and set the RTC. Provided there are no mistakes in the wiring, the display should start showing time, aslo the relay should click every 30 seconds.

If the Nano refuses to load, this may be because they are sold with two different bootloaders. (A bootloader is the short program the microcontoller uses to download and install an new program.) Go to 'Tools', and click on 'Processor'. Select the other bootloader and try again.

As a convenience the Sketch sets the Real Time Clock to the time the Sketch was compiled. Depending on the computer and Arduino used, the time may be a few seconds out-of-date.

To correct the time, go to 'Tools' and select Serial Monitor'. This will open a new window, which should be listing date times from the RTC. If garbage is appearing, the speed is probably wrong. Set it to 9600 bottom right.

Once the screen is listing valid date times, the RTC may be reset by typing in, top left, a string in the form:

dd/mo/yy hh:mm:ss

for example:  14/6/19 13:02:00

Type in a string that will be valid in a few minutes. Then, when an accurate clock reaches that time immediately press the 'Enter' key. This will set the RTC to the typed in time. The website time.is is a convenient accurate clock.

BUGS

None spotted by the limited testing I've done. I bet there's at least one and it's bleeding obvious! No prizes offered...

Dave

Edited By SillyOldDuffer on 14/06/2019 16:19:25

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