Date   

Re: Synchronome battery life

bailey.services@...
 

You are right, connected to power supply unit which masked the problem but again it stopped overnight. Investigating further found gap across contacts had increased. Having set the gaps at normal room temperature and finger tight it had loosened and widened perhaps exasperated by lower temperature.

Running again on 3 volts battery power and hopefully a years trouble free running ahead.
Howard


Re: Synchronome battery life

Andrew Nahum
 

I have run mine for many years on 3 volts - two Duracell D cells. Ihave consistently found that a pair lasts about a year, give or take. (I'm driving a single dial - just the clock's own one). If the latch was not re-setting after 45 days I would be looking at all the adjustments of coil-armature gap, contact gap and so on. It is true that fresh batteries can overcome some minor misadjustments in the re-latching process.

V best

Andrew


On Thu, Jan 14, 2021 at 8:47 PM bailey.services via groups.io <bailey.services=btinternet.com@groups.io> wrote:
My Synchronome #2054 ran for 45 days before latch failed to reset. Setup is transmitter and pilot at 11.5 ohms running at nominal 3 volts and 280mA from 2 Energizer Max D batteries. Thought it might do better, how do others get on with running on a small battery pack? 

Since Christmas week clock temperature has been dropping to 1.5C degrees overnight and not much warmer in the day against previous temperature around 12C. I expected the daily loss rate would be reduced as length of pendulum reduced but loss actually increased (from -2.5 to -3.5 per day). Maybe the cast iron bob is contracting more and increasing the overall length or is something else going on?

Not much showing on the forum so thought I might post my casual observations! 
All the best for 2021
Howard



Re: Synchronome battery life

Odell, Edward
 

Hi Howard,

 

That should be a standard 1930s synchronome. If it has a pilot dial then it is normally run on 6 V (nominally 4.5v master + 1.5 per slave, though of course as you say it is designed for constant current), and one set of cells should last you well over a year, probably two

 

your serial number is not listed in the serial number list on clockdoc (in the synchronome documents folder under synchronome at wp.clockdoc.org) . It would be great if you could check out the features and let us know what to add, especially if you have any accurate dating information.

 

Thanks

Eddy Odell

 

From: synchronome1@groups.io <synchronome1@groups.io> On Behalf Of bailey.services via groups.io
Sent: 14 January 2021 20:46
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Synchronome battery life

 

My Synchronome #2054 ran for 45 days before latch failed to reset. Setup is transmitter and pilot at 11.5 ohms running at nominal 3 volts and 280mA from 2 Energizer Max D batteries. Thought it might do better, how do others get on with running on a small battery pack? 

Since Christmas week clock temperature has been dropping to 1.5C degrees overnight and not much warmer in the day against previous temperature around 12C. I expected the daily loss rate would be reduced as length of pendulum reduced but loss actually increased (from -2.5 to -3.5 per day). Maybe the cast iron bob is contracting more and increasing the overall length or is something else going on?

Not much showing on the forum so thought I might post my casual observations! 
All the best for 2021
Howard


Re: Synchronome battery life

John Hubert
 

I can’t comment on power consumption as I run several clocks from a float charged battery (multiple C sized NiMH cells - now about 15 years old) - but 280 mA is on the low side for a Synchronome.  300 - 330 mA is more usual.  Low temperature will reduce battery capacity, though I don’t know by how much, and will also increase internal resistance, but I doubt this would be significant at approx 300 mA.

The rod is Invar, which has a very low temperature coefficient of expansion.  The iron bob will have a much higher coefficient of expansion.  Atmospheric pressure is also a factor.  

My own Synchronome sits in a relatively constant temperature and has a lead bob.  Variation (per day) is low with temperature change, typically 10 degrees Fahrenheit fall increases the clock ‘rate’ from approx 0 seconds per day to +0.3 second per day, but this is a very approximate measurement by simple visual observation against a Junghans radio controlled clock as reference (and averaged over a week rolling average).

John

On 14 Jan 2021, at 20:45, bailey.services via groups.io <bailey.services@...> wrote:

My Synchronome #2054 ran for 45 days before latch failed to reset. Setup is transmitter and pilot at 11.5 ohms running at nominal 3 volts and 280mA from 2 Energizer Max D batteries. Thought it might do better, how do others get on with running on a small battery pack? 

Since Christmas week clock temperature has been dropping to 1.5C degrees overnight and not much warmer in the day against previous temperature around 12C. I expected the daily loss rate would be reduced as length of pendulum reduced but loss actually increased (from -2.5 to -3.5 per day). Maybe the cast iron bob is contracting more and increasing the overall length or is something else going on?

Not much showing on the forum so thought I might post my casual observations! 
All the best for 2021
Howard




Synchronome battery life

bailey.services@...
 

My Synchronome #2054 ran for 45 days before latch failed to reset. Setup is transmitter and pilot at 11.5 ohms running at nominal 3 volts and 280mA from 2 Energizer Max D batteries. Thought it might do better, how do others get on with running on a small battery pack? 

Since Christmas week clock temperature has been dropping to 1.5C degrees overnight and not much warmer in the day against previous temperature around 12C. I expected the daily loss rate would be reduced as length of pendulum reduced but loss actually increased (from -2.5 to -3.5 per day). Maybe the cast iron bob is contracting more and increasing the overall length or is something else going on?

Not much showing on the forum so thought I might post my casual observations! 
All the best for 2021
Howard



Re: Master Clock contact spark quenching

Bob Holmstrom
 

On a visit to Sydney Australia in 2007, I was privileged to visit the building that houses Father O’Leary’s Clock (thought by some people to be a preaccessor to the Shortt Synchronome system).  I believe one of the members of this list was with me on the visit.

Anyway - Father O’Leary used a wiping contact version of a Hipp toggle switch - his prototype version was still attached to a laboratory wall.  As you can see in the photo below, the part of the switch that moves up and down is attached to a bracket on the wall and the ’notch’ and moving contact are attached to the pendulum rod.  The contact is wiped each time the ‘dangly bit’ catches in the moving notch.


O’Leary’s clock is shown in the two images below:

 

The more refined version of his Hipp switch is shown below:


More information on the clock is available in:

Horological Journal December  2004 and January 2005   and the NAWCC Bulletin February 1996 (A second clock by O’Leary is in the Smithsonian)

Bob Holmstrom
Editor
Horological Science Newsletter

On Jan 10, 2021, at 5:29 AMJanuary10, Simon Taylor <smktaylor1@...> wrote:

The contacts in the PO 36 were designed to 'wipe'. That is, that they continued to travel after contacting which led one to wipe over the other thus removing any oxide build up. I am not sure of the clock specifications, but for GPO 3000 relays, the contacts after meeting would then continue until a certain pre defined lift had carried the contacted spring clear of its buffer block (which it rested on) by a certain distance. this led to the contacts rubbing each other and so removing oxide build up.
-- 
Simon GPO Clocks
http://www.lightstraw.uk/gpo/clocksystems/index.html


Re: Master Clock contact spark quenching

Simon Taylor
 

The contacts in the PO 36 were designed to 'wipe'. That is, that they continued to travel after contacting which led one to wipe over the other thus removing any oxide build up. I am not sure of the clock specifications, but for GPO 3000 relays, the contacts after meeting would then continue until a certain pre defined lift had carried the contacted spring clear of its buffer block (which it rested on) by a certain distance. this led to the contacts rubbing each other and so removing oxide build up.
--
Simon GPO Clocks

http://www.lightstraw.uk/gpo/clocksystems/index.html


Re: Master Clock contact spark quenching

Ian Richardson
 

A wee bit off-topic, but.......

It should perhaps be remembered that, as Malcom has said, a reverse current is induced in the coil by the collapsing magnetic field when the circuit is broken.  When using a diode to quench this (which it does very effectively) the effective short circuit delays the collapse of the magnetic field in the magnet.  With the electric clocks with which we are all familiar, this is not usually a problem.  However, in the pipe organ field (of which I wrote a couple of days ago) this can be a problem as when a key is released there can be an noticeable lag before the valve closes - one reason why purists insist on purely mechanical actions in organs.

Ian R
Auvergne,
France



-----Original Message-----
From: Malcolm Rix <malcolmrix@...>
To: synchronome1@groups.io
Sent: Wed, 6 Jan 2021 16:43
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

When the switch breaks, current is still flowing in the magnet coil, as the magnetic field collapses in the iron core, reverse current is induced. Since the circuit is broken the voltage rises very high and a spark may jump the gap. When synchronomes were in service a resistor was used to drain the current and avoid the voltage reaching a level that would spark. The modern way is to use a silicon power diode (e.g. 1N4001) mounted in reverse across the switch. These were not available in the clock’s heyday, hence the resistor. A capacitor might delay the rise of the peak, but either a resistor or diode is really the way to go.

Malcolm

On Jan 6, 2021, at 23:23, Andrew Nahum <andrew.nahum@...> wrote:


I have often wondered why spark quenching can’t be done better with a capacitor as used across the breaker points in all older style automotive ignitions.  Can anyone explain why we stick with the Synchronome resistor?


On 5 Jan 2021, at 09:40, John Haine <john.haine@...> wrote:

As it's now 2021 you could consider using a solid state relay - silent, should last for ever, no inductive kick to make any arcs across the clock contacts.

https://uk.rs-online.com/web/p/solid-state-relays/9061079/

RS sell 'em in 5s which is inconvenient unless you have a use for the other 4, or could share a pack.  There are probably other suppliers - in fact eBay:
have them at double the price in ones though.


Re: Master Clock contact spark quenching

Malcolm Rix
 

When the switch breaks, current is still flowing in the magnet coil, as the magnetic field collapses in the iron core, reverse current is induced. Since the circuit is broken the voltage rises very high and a spark may jump the gap. When synchronomes were in service a resistor was used to drain the current and avoid the voltage reaching a level that would spark. The modern way is to use a silicon power diode (e.g. 1N4001) mounted in reverse across the switch. These were not available in the clock’s heyday, hence the resistor. A capacitor might delay the rise of the peak, but either a resistor or diode is really the way to go.

Malcolm

On Jan 6, 2021, at 23:23, Andrew Nahum <andrew.nahum@...> wrote:

I have often wondered why spark quenching can’t be done better with a capacitor as used across the breaker points in all older style automotive ignitions.  Can anyone explain why we stick with the Synchronome resistor?


On 5 Jan 2021, at 09:40, John Haine <john.haine@...> wrote:

As it's now 2021 you could consider using a solid state relay - silent, should last for ever, no inductive kick to make any arcs across the clock contacts.

https://uk.rs-online.com/web/p/solid-state-relays/9061079/

RS sell 'em in 5s which is inconvenient unless you have a use for the other 4, or could share a pack.  There are probably other suppliers - in fact eBay:
have them at double the price in ones though.


Re: Master Clock contact spark quenching

John Hubert
 

Interesting.  The Silent Electric (closely related to early GPO clocks) uses make before break and resistors (unknown, but very probably just like the GPO ones).  The were designed to work with Silent Electric’s own ’Silectock’ rotary armature mechanism at 250 mA and some systems used many dials.  No mention is made of relays in the contemporary literature (1919 catalogue) which states;

“The contact arrangement consists of two pairs of platinum points - one being for the line circuit for the dials and the other for the shunt or short circuit, according to whether the clocks are operated from battery or from electric light supply.  The motion given to the contact springs in conjunction with this method of cutting out the shunt, except for the instant prior to breaking the circuit, results in sparkless action”.

The terminals in the clocks are marked “Pendulum Battery”, “Dials Battery” and “Dials”.  The same contacts and markings are used in both the 1/2 second and 1 second pendulum versions of the clocks.

John

On 8 Jan 2021, at 14:12, Simon Taylor <smktaylor1@...> wrote:

The GPO used a 200 ohm resistor in series with a 1 micro farad capacitor across the contacts on later type 36 clocks with simple make contacts. The earlier types with make before break contacts had a 2000 ohm resistor. and worked with the earlier relay 90A which had 2 x 500 ohm coils in parallel.

All of the contacts are made of 10% iridium and 90% platinum. The hipp toggle contacts pass between 400-500mA for the pendulum drive coil. Although running a GPO slave cct direct it is quite possible, I would still recommend using either traditional relay (coil 2000-5000 ohms) or a solid state device or arduino system.
--
Simon GPO Clocks

http://www.lightstraw.uk/gpo/clocksystems/index.html



Re: Master Clock contact spark quenching

markotime
 

Another thing about contacts: Some level of current must be carried through mechanical contacts
to prevent buildup of oxide or other contaminants which will eventually inhibit conductivity.  If
memory serves me correctly, "sealing" current is the proper term.  For Hipp, there is probably
enough wiping action to prevent buildup if the "needle" is part of the circuit.  I'm inclined to use
optical devices rather than mechanical contacts.
Haven't yet worked my way thru Arduino logic for a Hipp solution.

On 1/8/2021 6:12 AM, Simon Taylor wrote:

The GPO used a 200 ohm resistor in series with a 1 micro farad capacitor across the contacts on later type 36 clocks with simple make contacts. The earlier types with make before break contacts had a 2000 ohm resistor. and worked with the earlier relay 90A which had 2 x 500 ohm coils in parallel.

All of the contacts are made of 10% iridium and 90% platinum. The hipp toggle contacts pass between 400-500mA for the pendulum drive coil. Although running a GPO slave cct direct it is quite possible, I would still recommend using either traditional relay (coil 2000-5000 ohms) or a solid state device or arduino system.
--
Simon GPO Clocks

http://www.lightstraw.uk/gpo/clocksystems/index.html



Re: Master Clock contact spark quenching

Simon Taylor
 

The GPO used a 200 ohm resistor in series with a 1 micro farad capacitor across the contacts on later type 36 clocks with simple make contacts. The earlier types with make before break contacts had a 2000 ohm resistor. and worked with the earlier relay 90A which had 2 x 500 ohm coils in parallel.

All of the contacts are made of 10% iridium and 90% platinum. The hipp toggle contacts pass between 400-500mA for the pendulum drive coil. Although running a GPO slave cct direct it is quite possible, I would still recommend using either traditional relay (coil 2000-5000 ohms) or a solid state device or arduino system.
--
Simon GPO Clocks

http://www.lightstraw.uk/gpo/clocksystems/index.html


Re: Master Clock contact spark quenching

markotime
 

They didn't have Silicon diodes in Strowger days, only Selenium, which devices were
leaky and bulky.  R/C was the appropriate tech.  Now, Si.

On 1/7/2021 3:03 PM, Ian Richardson via groups.io wrote:
Hi Darren,

You are quite correct, but there are also other ways to minimise the voltage across the contacts as they open.  One is to put a capacitor in series with the power supply such that it is the capacitor charging current which drives the solenoid, then blocks any further current flow.  This approach works well with clocks whose impulse is prolonged, eg Brillié, but may not work for the very short impulse of a Synchronome.  Another is to use make-before-break contacts arranged such that the coil is shunted before the supply contacts open.  This is used on GPO Type 36 clocks. A less familiar approach was used by Matheus Hipp whereby the make-before-break switch actually short circuits both the coils and the supply!  In that case, a resistor was put in series with the power supply to avoid the direct short.

I made full use of the capacitor blocking approach in my electrically reset gravity escapement clock (of which I have written before) wherein the gravity arms form the poles of a reversing switch, but the driving current comes from charging and discharging capacitors so arranged that the operating current is applied via the capacitors on making contact, but when the contact is broken there is no current flowing.

While on this subject, it is worth remembering that Strowger type telephone exchanges used hundreds if not thousands of relays and other electromagnetic switching devices and they nearly always used the R/C type of snubber across the contacts - so they must have reckoned it to be a good solution to the sparking issue!

Best regards,
Ian R
Auvergne,
France



-----Original Message-----
From: Darren Conway <darren.conway@...>
To: synchronome1@groups.io
Sent: Thu, 7 Jan 2021 20:52
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

Hi
There are two parts to this problem.
One is to reduce the back emf from the coil that generates the voltage to arc across the opening contacts.  A diode across the coil will achieve this.
Two is to maintain a near zero voltage across the contacts as they open, for long enough to open far enough to prevent an arc forming.  This is solved with an RC snubber across the contacts. 

Regards

Darren Conway
36 Orr Crescent
Lower Hutt
New Zealand
ph +64  (0)4 569 1963

On 7.01.21 11:33 pm, Ian Richardson via groups.io wrote:
In the pipe organ world, the use of diodes in direct electric actions is standard practice.  I have just fitted up a direct action unit extension organ with about 200 electromagnetic valves, each runs on 15 vdc. and carries a current of about 250mA.  Each coil is shunted with 1N400X diodes or equivalent. There is no sparking - imagine if there was, the organ woiuld break down every day as the coils are activated hundreds of times with each performance!  The diodes cost about €1 per 100.

The point about polarity is, of course, valid but simply solved by using a high current silicon diode in series with the power supply.  If connected the correct way round, all works well; if the wrong way round, it doesn't work at all, so it "fails safe".

Ian R
Auvergne,
France



-----Original Message-----
From: John Hubert <jfphubert@...>
To: synchronome1@groups.io
Sent: Thu, 7 Jan 2021 11:17
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

I do just as you suggest on all my dials and masters.  1N400X series diodes.  The maintaining of current is minimal (looked some years ago with an oscilloscope and it was insignificant).  There is typically some variation of impulse length dependant on the master anyway (Gents tend to be longer and early Synchronome clocks rather short - lighter parts?).  Typically, the coil carries about 300 mA and has a resistance of about 5 Ohms, with a parallel resistor of about 50 Ohms.

Diodes work well - but of course you have to have the right polarity.

John

On 7 Jan 2021, at 10:06, John Haine <john.haine@...> wrote:

Surely now we have cheap reliable silicon diodes the best approach is the now-standard practice of connecting a diode across the coil so that when the contact opens the diode shorts out the inductive kick?  The diode should be reverse biased when the coil is energised.  The only snag with this is that the diode maintains the current when the contact opens for a period which may cause a problem.  That can be made shorter by putting a resistor in series with the diode to dissipate the stored energy more quickly at the expense of a higher voltage.  For example, if the coil carried 1 amp when the contact was closed, and the resistor was 100 ohms, the peak backswing voltage would be 100 volts, quite a lot but probably not enough to cause breakdown in the gap.


Virus-free. www.avast.com


Re: Master Clock contact spark quenching

Ian Richardson
 

Hi Darren,

You are quite correct, but there are also other ways to minimise the voltage across the contacts as they open.  One is to put a capacitor in series with the power supply such that it is the capacitor charging current which drives the solenoid, then blocks any further current flow.  This approach works well with clocks whose impulse is prolonged, eg Brillié, but may not work for the very short impulse of a Synchronome.  Another is to use make-before-break contacts arranged such that the coil is shunted before the supply contacts open.  This is used on GPO Type 36 clocks. A less familiar approach was used by Matheus Hipp whereby the make-before-break switch actually short circuits both the coils and the supply!  In that case, a resistor was put in series with the power supply to avoid the direct short.

I made full use of the capacitor blocking approach in my electrically reset gravity escapement clock (of which I have written before) wherein the gravity arms form the poles of a reversing switch, but the driving current comes from charging and discharging capacitors so arranged that the operating current is applied via the capacitors on making contact, but when the contact is broken there is no current flowing.

While on this subject, it is worth remembering that Strowger type telephone exchanges used hundreds if not thousands of relays and other electromagnetic switching devices and they nearly always used the R/C type of snubber across the contacts - so they must have reckoned it to be a good solution to the sparking issue!

Best regards,
Ian R
Auvergne,
France



-----Original Message-----
From: Darren Conway <darren.conway@...>
To: synchronome1@groups.io
Sent: Thu, 7 Jan 2021 20:52
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

Hi
There are two parts to this problem.
One is to reduce the back emf from the coil that generates the voltage to arc across the opening contacts.  A diode across the coil will achieve this.
Two is to maintain a near zero voltage across the contacts as they open, for long enough to open far enough to prevent an arc forming.  This is solved with an RC snubber across the contacts. 

Regards

Darren Conway
36 Orr Crescent
Lower Hutt
New Zealand
ph +64  (0)4 569 1963

On 7.01.21 11:33 pm, Ian Richardson via groups.io wrote:
In the pipe organ world, the use of diodes in direct electric actions is standard practice.  I have just fitted up a direct action unit extension organ with about 200 electromagnetic valves, each runs on 15 vdc. and carries a current of about 250mA.  Each coil is shunted with 1N400X diodes or equivalent. There is no sparking - imagine if there was, the organ woiuld break down every day as the coils are activated hundreds of times with each performance!  The diodes cost about €1 per 100.

The point about polarity is, of course, valid but simply solved by using a high current silicon diode in series with the power supply.  If connected the correct way round, all works well; if the wrong way round, it doesn't work at all, so it "fails safe".

Ian R
Auvergne,
France



-----Original Message-----
From: John Hubert <jfphubert@...>
To: synchronome1@groups.io
Sent: Thu, 7 Jan 2021 11:17
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

I do just as you suggest on all my dials and masters.  1N400X series diodes.  The maintaining of current is minimal (looked some years ago with an oscilloscope and it was insignificant).  There is typically some variation of impulse length dependant on the master anyway (Gents tend to be longer and early Synchronome clocks rather short - lighter parts?).  Typically, the coil carries about 300 mA and has a resistance of about 5 Ohms, with a parallel resistor of about 50 Ohms.

Diodes work well - but of course you have to have the right polarity.

John

On 7 Jan 2021, at 10:06, John Haine <john.haine@...> wrote:

Surely now we have cheap reliable silicon diodes the best approach is the now-standard practice of connecting a diode across the coil so that when the contact opens the diode shorts out the inductive kick?  The diode should be reverse biased when the coil is energised.  The only snag with this is that the diode maintains the current when the contact opens for a period which may cause a problem.  That can be made shorter by putting a resistor in series with the diode to dissipate the stored energy more quickly at the expense of a higher voltage.  For example, if the coil carried 1 amp when the contact was closed, and the resistor was 100 ohms, the peak backswing voltage would be 100 volts, quite a lot but probably not enough to cause breakdown in the gap.


Virus-free. www.avast.com


Re: T&N switching, was Solari Flip Clock Driver

Ian Richardson
 

Ernie,

In order to photograph the commutator switch, I will have to stop the clock and lift out the movement.  The commutator is mounted on the back board, but the spindle which drives it is part of the clock movement, so I'll endeavor to show both parts although I would assume that the part which is on the clock movement is still existing (or is it?).

I will do all this this weekend, assuming that you can wait a bit!

I have to confess that I have little or no understanding of all the microelectronic stuff - all my clocks run "as built".

Best regards,
Ian R



-----Original Message-----
From: Ernie Jenson via groups.io <erniejenson@...>
To: synchronome1@groups.io <synchronome1@groups.io>
Sent: Thu, 7 Jan 2021 21:09
Subject: Re: [synchronomeelectricclock] Solari Flip Clock Driver

Thanks Ian for the offer of pictures.  Thanks Thomas for the suggestion of the h-bridge circuit.  Since I have modefied the T&N to deliver a contact closure for 10 seconds every minute, I couldn't figure out how to make that work with out a micro controller to complete the operation.  I programed a micro controller but encountered problems with interference from the many master clocks in the room on the same circuit.  I programed and reprogramed and then decided that this was not the right way to go.  Whoever gets the clock after me will most likely not be able to maintain the circuit.  My choise was to buy another T&N to get the part and keep the clock original or build a replacement part that does the job in the manor that would have been used at the time the clock was new.  My first attemp at a mechanical device was also a failure.  I now need to look at the way that T&N solved the problem.  I have an ENEM master clock and their solution to the problem is far too complex.  I can't find another T&N to purchase.
Thanks for all the help, I really appreciate the effort.
Ernie



Re: Solari Flip Clock Driver

Ernie Jenson
 

Thanks Ian for the offer of pictures.  Thanks Thomas for the suggestion of the h-bridge circuit.  Since I have modefied the T&N to deliver a contact closure for 10 seconds every minute, I couldn't figure out how to make that work with out a micro controller to complete the operation.  I programed a micro controller but encountered problems with interference from the many master clocks in the room on the same circuit.  I programed and reprogramed and then decided that this was not the right way to go.  Whoever gets the clock after me will most likely not be able to maintain the circuit.  My choise was to buy another T&N to get the part and keep the clock original or build a replacement part that does the job in the manor that would have been used at the time the clock was new.  My first attemp at a mechanical device was also a failure.  I now need to look at the way that T&N solved the problem.  I have an ENEM master clock and their solution to the problem is far too complex.  I can't find another T&N to purchase.
Thanks for all the help, I really appreciate the effort.
Ernie



Re: Master Clock contact spark quenching

Darren Conway
 

Hi

There are two parts to this problem.

One is to reduce the back emf from the coil that generates the voltage to arc across the opening contacts.  A diode across the coil will achieve this.

Two is to maintain a near zero voltage across the contacts as they open, for long enough to open far enough to prevent an arc forming.  This is solved with an RC snubber across the contacts. 


Regards

Darren Conway
36 Orr Crescent
Lower Hutt
New Zealand
ph +64  (0)4 569 1963

On 7.01.21 11:33 pm, Ian Richardson via groups.io wrote:
In the pipe organ world, the use of diodes in direct electric actions is standard practice.  I have just fitted up a direct action unit extension organ with about 200 electromagnetic valves, each runs on 15 vdc. and carries a current of about 250mA.  Each coil is shunted with 1N400X diodes or equivalent. There is no sparking - imagine if there was, the organ woiuld break down every day as the coils are activated hundreds of times with each performance!  The diodes cost about €1 per 100.

The point about polarity is, of course, valid but simply solved by using a high current silicon diode in series with the power supply.  If connected the correct way round, all works well; if the wrong way round, it doesn't work at all, so it "fails safe".

Ian R
Auvergne,
France



-----Original Message-----
From: John Hubert <jfphubert@...>
To: synchronome1@groups.io
Sent: Thu, 7 Jan 2021 11:17
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

I do just as you suggest on all my dials and masters.  1N400X series diodes.  The maintaining of current is minimal (looked some years ago with an oscilloscope and it was insignificant).  There is typically some variation of impulse length dependant on the master anyway (Gents tend to be longer and early Synchronome clocks rather short - lighter parts?).  Typically, the coil carries about 300 mA and has a resistance of about 5 Ohms, with a parallel resistor of about 50 Ohms.

Diodes work well - but of course you have to have the right polarity.

John

On 7 Jan 2021, at 10:06, John Haine <john.haine@...> wrote:

Surely now we have cheap reliable silicon diodes the best approach is the now-standard practice of connecting a diode across the coil so that when the contact opens the diode shorts out the inductive kick?  The diode should be reverse biased when the coil is energised.  The only snag with this is that the diode maintains the current when the contact opens for a period which may cause a problem.  That can be made shorter by putting a resistor in series with the diode to dissipate the stored energy more quickly at the expense of a higher voltage.  For example, if the coil carried 1 amp when the contact was closed, and the resistor was 100 ohms, the peak backswing voltage would be 100 volts, quite a lot but probably not enough to cause breakdown in the gap.


Virus-free. www.avast.com


Re: Master Clock contact spark quenching

John Haine
 
Edited

Well, I said "may cause a problem".  This is based on one case of which I can't recall the details but I think there was a transistor driving a relay which stayed "on" longer than desired when the transistor switched off because of the diode.  Easily solved by a series resistor if needed but as people point out it probably won't be.


Re: Master Clock contact spark quenching

John Hubert
 

If this is done in the musical world - then I think the assumption that any effect on the timing (i.e. lengthening of coil current duration) is insignificant.  

In a clock circuit, if you do get the polarity wrong, the diode (assume 1N400X type) can cope with the forward current (about 300 mA and it is OK to an Amp) and the dial concerned dial simply doesn’t advance - so easily spotted and corrected.  I have never in 10 years with maybe 50 dials running knowingly had a diode fail.

John

On 7 Jan 2021, at 10:33, Ian Richardson via groups.io <irichar361@...> wrote:

In the pipe organ world, the use of diodes in direct electric actions is standard practice.  I have just fitted up a direct action unit extension organ with about 200 electromagnetic valves, each runs on 15 vdc. and carries a current of about 250mA.  Each coil is shunted with 1N400X diodes or equivalent. There is no sparking - imagine if there was, the organ woiuld break down every day as the coils are activated hundreds of times with each performance!  The diodes cost about €1 per 100.

The point about polarity is, of course, valid but simply solved by using a high current silicon diode in series with the power supply.  If connected the correct way round, all works well; if the wrong way round, it doesn't work at all, so it "fails safe".

Ian R
Auvergne,
France





Re: Master Clock contact spark quenching

Ian Richardson
 

In the pipe organ world, the use of diodes in direct electric actions is standard practice.  I have just fitted up a direct action unit extension organ with about 200 electromagnetic valves, each runs on 15 vdc. and carries a current of about 250mA.  Each coil is shunted with 1N400X diodes or equivalent. There is no sparking - imagine if there was, the organ woiuld break down every day as the coils are activated hundreds of times with each performance!  The diodes cost about €1 per 100.

The point about polarity is, of course, valid but simply solved by using a high current silicon diode in series with the power supply.  If connected the correct way round, all works well; if the wrong way round, it doesn't work at all, so it "fails safe".

Ian R
Auvergne,
France



-----Original Message-----
From: John Hubert <jfphubert@...>
To: synchronome1@groups.io
Sent: Thu, 7 Jan 2021 11:17
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

I do just as you suggest on all my dials and masters.  1N400X series diodes.  The maintaining of current is minimal (looked some years ago with an oscilloscope and it was insignificant).  There is typically some variation of impulse length dependant on the master anyway (Gents tend to be longer and early Synchronome clocks rather short - lighter parts?).  Typically, the coil carries about 300 mA and has a resistance of about 5 Ohms, with a parallel resistor of about 50 Ohms.

Diodes work well - but of course you have to have the right polarity.

John

On 7 Jan 2021, at 10:06, John Haine <john.haine@...> wrote:

Surely now we have cheap reliable silicon diodes the best approach is the now-standard practice of connecting a diode across the coil so that when the contact opens the diode shorts out the inductive kick?  The diode should be reverse biased when the coil is energised.  The only snag with this is that the diode maintains the current when the contact opens for a period which may cause a problem.  That can be made shorter by putting a resistor in series with the diode to dissipate the stored energy more quickly at the expense of a higher voltage.  For example, if the coil carried 1 amp when the contact was closed, and the resistor was 100 ohms, the peak backswing voltage would be 100 volts, quite a lot but probably not enough to cause breakdown in the gap.

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