Master Clock contact spark quenching


Darren Conway
 

Hi

I now have 1 Master and 2 Slaves running from a 12V supply.  There is enough resistance to limit the current to within spec (~240mA).

I am seeing arcing across the Master clock contacts.    This can't be good.

Is there a standard solution to this problem?  If not, I would add an RC snubber between the top terminal and the cast iron frame from the back.


Regards

Darren Conway




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Tracy and Raymond van Orsoy de Flines
 

Best is to use a relay. I got a Gents masterclock (Hipp Toggle) and run the 30 second slave clocks through a relay.


On Tue, 5 Jan 2021, 12:50 Darren Conway <darren.conway@...> wrote:

Hi

I now have 1 Master and 2 Slaves running from a 12V supply.  There is enough resistance to limit the current to within spec (~240mA).

I am seeing arcing across the Master clock contacts.    This can't be good.

Is there a standard solution to this problem?  If not, I would add an RC snubber between the top terminal and the cast iron frame from the back.


Regards

Darren Conway




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neil
 

Hi Darren,
             Raymond is correct ...the clock contacts are only rated to drive the old post office 2000 series relays, which pull little current, and the slaves are driven by the relay. I also have a gents po36 hipp toggle clock and I operate the slaves via a small Philips relay inside the clock, so the clock contacts only see the relay current. If you like I can post you a suitable relay if you tell me what voltage you are running.
Neil

On Tue, 5 Jan 2021, 12:55 pm Tracy and Raymond van Orsoy de Flines, <raytray.van@...> wrote:
Best is to use a relay. I got a Gents masterclock (Hipp Toggle) and run the 30 second slave clocks through a relay.

On Tue, 5 Jan 2021, 12:50 Darren Conway <darren.conway@...> wrote:

Hi

I now have 1 Master and 2 Slaves running from a 12V supply.  There is enough resistance to limit the current to within spec (~240mA).

I am seeing arcing across the Master clock contacts.    This can't be good.

Is there a standard solution to this problem?  If not, I would add an RC snubber between the top terminal and the cast iron frame from the back.


Regards

Darren Conway




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John Haine
 

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.


Ian Richardson
 

Pardon me being thick, but the RS relay you quote doesn't seem to specify a driver voltage?

Ian R



-----Original Message-----
From: John Haine <john.haine@...>
To: synchronome1@groups.io
Sent: Tue, 5 Jan 2021 10:40
Subject: Re: [synchronomeelectricclock] Master Clock contact spark quenching

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.


John Haine
 

That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 


Darren Conway
 

Hi

If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice.  I already have one.

An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock.  Easier than building from discrete components.  If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.

I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock.   Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors.   If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections.    The only problem is that shipping times from China are currently about 3 to 6 months.


The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.

Regards

Darren Conway
New Zealand


On 5.01.21 10:54 pm, John Haine wrote:
That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 

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Darren Conway
 

Hi

Here is a Aduino  Motor shield that would be ideal for driving the Gents and Solari slave  clocks. 


Regards

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

On 6.01.21 7:12 am, Darren Conway wrote:

Hi

If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice.  I already have one.

An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock.  Easier than building from discrete components.  If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.

I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock.   Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors.   If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections.    The only problem is that shipping times from China are currently about 3 to 6 months.


The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.

Regards

Darren Conway
New Zealand


On 5.01.21 10:54 pm, John Haine wrote:
That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 

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Tony Nixon
 

Darren,
I am really surprised that the delivery time from China to NZ is so long.  I have been buying Arduino and other small electronic parts from China using ebay for the last 5 years, generally keeping orders below GBP10 to avoid attracting duty.  Delivery has usually been 2-3 weeks (and free too!)  Most of the same parts can also be purchased from UK suppliers on a weeks turn round but at about double the price.  Are there no similar suppliers in NZ?

I have noticed in the last two months though that free delivery seems to be disappearing, I read somewhere that some concessionary deals offerd to the Chinese for cheap shipment have now ended.  A more worrying development that I have just started to hear about is that post Brenxit the UK is apparently going to require all suppliers selling into the UK to register to pay VAT with the UK authorities.  One European supplier (of bike parts) has apparently already decided no longer to deal with customers in the UK.

I am just beginning to experiment with an ESP8266 Node MCU to get a time stamp from NTP to log temperature, pressure and error on my Pulsynetic.

Regards

Tony

On 5 Jan 2021, at 19:48, Darren Conway <darren.conway@...> wrote:

Hi

Here is a Aduino  Motor shield that would be ideal for driving the Gents and Solari slave  clocks. 


Regards

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

On 6.01.21 7:12 am, Darren Conway wrote:

Hi

If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice.  I already have one.

An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock.  Easier than building from discrete components.  If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.

I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock.   Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors.   If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections.    The only problem is that shipping times from China are currently about 3 to 6 months.


The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.

Regards

Darren Conway
New Zealand


On 5.01.21 10:54 pm, John Haine wrote:
That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 

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neil
 

Darren - i am still buying electronic supplies from China, and turnaround is a few weeks. If the value is low, then GST is not an issue - so far anyway.
Neil Jepsen. B.Sc. M.Sc(Hons).CPL.MASNZ.
Jepsen Acoustics & Electronics Ltd
22 Domain Street
Palmerston North.
New Zealand.
Ph +64 6 3577539  Mob 0274428094
Web site: www.noiseandweather.co.nz
          www.noiseandweather.com  
E.& O.E.
On 6/01/2021 11:55 am, Tony Nixon wrote:

Darren,
I am really surprised that the delivery time from China to NZ is so long.  I have been buying Arduino and other small electronic parts from China using ebay for the last 5 years, generally keeping orders below GBP10 to avoid attracting duty.  Delivery has usually been 2-3 weeks (and free too!)  Most of the same parts can also be purchased from UK suppliers on a weeks turn round but at about double the price.  Are there no similar suppliers in NZ?

I have noticed in the last two months though that free delivery seems to be disappearing, I read somewhere that some concessionary deals offerd to the Chinese for cheap shipment have now ended.  A more worrying development that I have just started to hear about is that post Brenxit the UK is apparently going to require all suppliers selling into the UK to register to pay VAT with the UK authorities.  One European supplier (of bike parts) has apparently already decided no longer to deal with customers in the UK.

I am just beginning to experiment with an ESP8266 Node MCU to get a time stamp from NTP to log temperature, pressure and error on my Pulsynetic.

Regards

Tony
On 5 Jan 2021, at 19:48, Darren Conway <darren.conway@...> wrote:

Hi

Here is a Aduino  Motor shield that would be ideal for driving the Gents and Solari slave  clocks. 


Regards

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

On 6.01.21 7:12 am, Darren Conway wrote:

Hi

If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice.  I already have one.

An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock.  Easier than building from discrete components.  If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.

I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock.   Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors.   If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections.    The only problem is that shipping times from China are currently about 3 to 6 months.


The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.

Regards

Darren Conway
New Zealand


On 5.01.21 10:54 pm, John Haine wrote:
That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 

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Darren Conway
 

Hi

Prior to Covid, delivery from China was usually 4-8 weeks.   I currently have 13 items on order that I am waiting for.  The oldest order is 22 Oct 2020. 

The problem here is that most of those small packages were carried by passenger aircraft.  Those services aren't running and there is big demand the slower and now more expensive channels.


Regards

Darren Conway
New Zealand


On 6.01.21 11:55 am, Tony Nixon wrote:
Darren,
I am really surprised that the delivery time from China to NZ is so long.  I have been buying Arduino and other small electronic parts from China using ebay for the last 5 years, generally keeping orders below GBP10 to avoid attracting duty.  Delivery has usually been 2-3 weeks (and free too!)  Most of the same parts can also be purchased from UK suppliers on a weeks turn round but at about double the price.  Are there no similar suppliers in NZ?

I have noticed in the last two months though that free delivery seems to be disappearing, I read somewhere that some concessionary deals offerd to the Chinese for cheap shipment have now ended.  A more worrying development that I have just started to hear about is that post Brenxit the UK is apparently going to require all suppliers selling into the UK to register to pay VAT with the UK authorities.  One European supplier (of bike parts) has apparently already decided no longer to deal with customers in the UK.

I am just beginning to experiment with an ESP8266 Node MCU to get a time stamp from NTP to log temperature, pressure and error on my Pulsynetic.

Regards

Tony
On 5 Jan 2021, at 19:48, Darren Conway <darren.conway@...> wrote:

Hi

Here is a Aduino  Motor shield that would be ideal for driving the Gents and Solari slave  clocks. 


Regards

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

On 6.01.21 7:12 am, Darren Conway wrote:

Hi

If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice.  I already have one.

An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock.  Easier than building from discrete components.  If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.

I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock.   Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors.   If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections.    The only problem is that shipping times from China are currently about 3 to 6 months.


The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.

Regards

Darren Conway
New Zealand


On 5.01.21 10:54 pm, John Haine wrote:
That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 

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Thomas D. Erb
 


Andrew Nahum
 

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.


John Hubert
 

Can anyone explain why we stick with the Synchronome resistor?

I can make a few guesses;
  1. In a Synchronome, the ‘ON period’ is very short - a few hundred milliseconds per minute, so the losses in a resistor (which only occur in the ON period) are similarly low.  In a car it is MUCH higher.
  2. In the pre WW1 days, resistors were easy.  Larger value capacitors were not.
  3. Many higher value capacitors were then both bulky and relatively expensive - and many (all electrolytic types) were polarity sensitive.
  4. The inductance across a car system is near enough fixed - whereas a clock system will vary from system to system (number of dials) - and so ‘one size fits all’ may not be optimised.
  5. The increase in power consumption for a Synchronome was approx 10%, which is not very significant.

Synchronome and G&J used a resistor across each coil (both master movement and slave dials) whereas Gents only fitted a (capacitor based) system in the master - not the slave dials.  Gents do however have very heavy duty contacts.

One manufacturer whom used an interesting ‘different’ approach was the original Princeps system.  A very light contact based on the pendulum rod ‘made’ the contact (there is no spark on the ‘make’) - but the current break was done by a much heavier duty ‘break’ contact - driven by an electromagnet giving a fast break.  The light contact set only opened after the current had already stopped - so never arcs.

John

On 6 Jan 2021, at 15:22, Andrew Nahum <andrew.nahum@...> wrote:

Can anyone explain why we stick with the Synchronome resistor?


Darren Conway
 

Hi

The problem with a capacitor across the contacts is that when the contacts first touch, the capacitor charging current is very high. This damages the contacts.

The problem with a resistor is that when the contacts open, full current is flowing through all the coils.  The coils try to maintain this flow by raising the voltage (back EMF).  This can easily reach 100's of volts.   This voltage will arc across the open contacts.  The resistor will only reduce the current.

The solution is to use an RC snubber circuit as described here

These reduce the initial capacitor charge current and hold the voltage across the contacts low enough  for long enough to allow the contacts separate far enough to prevent an arc forming.    When applied to a Synchronome with a 12V supply, these formula limit the initial charge current to "only" 24 Amps with a 1ohm resistor.  I would increase the resistor 10x.  This initial charge current is overstated because with a 12V supply, I have 54 ohms in circuit to limit the current to 220mA required by the slaves.   

The other part of the approach is to reduce the back emf from each coil.  This can be effectively done with diodes but that requires making sure each slave coil has the right polarity connected.    Not difficult to do.

An alternative is to connect two zener diodes, back to back, in series across each coil.  Each zener should be rated to at least twice the supply voltage.   These devices were not available when Synchronomes were made.  


Another alternative is to use a driver circuit to separate the contacts from the coil/slave circuit.  This works except for the coil in the master clock and the coil for the in-case slave.


Regards

Darren Conway
Lower Hutt
New Zealand


On 7.01.21 5:12 am, John Hubert wrote:
Can anyone explain why we stick with the Synchronome resistor?

I can make a few guesses;
  1. In a Synchronome, the ‘ON period’ is very short - a few hundred milliseconds per minute, so the losses in a resistor (which only occur in the ON period) are similarly low.  In a car it is MUCH higher.
  2. In the pre WW1 days, resistors were easy.  Larger value capacitors were not.
  3. Many higher value capacitors were then both bulky and relatively expensive - and many (all electrolytic types) were polarity sensitive.
  4. The inductance across a car system is near enough fixed - whereas a clock system will vary from system to system (number of dials) - and so ‘one size fits all’ may not be optimised.
  5. The increase in power consumption for a Synchronome was approx 10%, which is not very significant.

Synchronome and G&J used a resistor across each coil (both master movement and slave dials) whereas Gents only fitted a (capacitor based) system in the master - not the slave dials.  Gents do however have very heavy duty contacts.

One manufacturer whom used an interesting ‘different’ approach was the original Princeps system.  A very light contact based on the pendulum rod ‘made’ the contact (there is no spark on the ‘make’) - but the current break was done by a much heavier duty ‘break’ contact - driven by an electromagnet giving a fast break.  The light contact set only opened after the current had already stopped - so never arcs.

John

On 6 Jan 2021, at 15:22, Andrew Nahum <andrew.nahum@...> wrote:

Can anyone explain why we stick with the Synchronome resistor?


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John Haine
 

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.


John Hubert
 

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.


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.


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





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.