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  1. #1

    Default Correct Voltage for Gents Pulsynetic Master Clock

    I have just finsihed refurbishing a Gents Pulsynetic Master Clock and was wondering what the correct voltage is for this style of clock. I thought I should ask before accidentally connecting too much voltage and damaging the coils.

    In case it matters, it is a master clock with one slave dial attached.

    The only information I was able to find online said 12V to 24V but that is a pretty broad range.

    Any help would be appreciated.

    Michael

  2. #2

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    The Gents master and slave clocks usually have a series system for all the dials which runs at around 180 to 200 mA's.

    If a 12 Volt or 24 Volts supply is used an appropiate series resistor shall be used in series with the powersupply to the clock line.

    Most Gents coils are 4 Ohms, (from memory) at 200 mA the voltage across the coil is 0.8 Volts. ( U=I x R ).

    In you case, the coils from the gravity mechanism 0.8 Volts,
    The clock dial, 0.8 Volts and the slave dial 0.8 Volts. Total 2.4 Volts.

    If you use a 12 Volts DC supply then:
    12-2.4=9.6Volts
    at 200 mA's
    R = 48 Ohms.
    From P= I≤ x R, the power rating of the resistor shall be 1.92 Watts

    A 48 Ohms resistor is non E12 series. So a 47 Ohms 5 Watt ceramic resistor from Jaycars, Dick Smiths or any electronics shop will do. Cost less then 0.5 dollar.

    You can try a 68, 56 or 47 ohms Resistor.
    sometimes when only a few clocks are in series it may well work fine at 150 mA's which will reduce the noise every 30 seconds.

    Regards

    Raymond

  3. #3
    Registered User Hans Vrolijk's Avatar
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    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Michael,

    The Gents Pulsynetic system is designed to run on 220 mAmps. So the voltage is not important, but the current is. There should be a adjustable resistor in the clock to set the current.
    Interested in my electric clocks?
    www.vrolijk-clocks.nl

  4. #4

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Thank you Hans and Raymond,

    If you can please excuse my electrical ignorance I have some additional questions. I am going to explain what I have done first then questions second.

    1) I tried two "D" cell batteries in series to create 3 volts. I have no idea how many milliamps this creates. With this attempt the magnets did not charge sufficiently.

    2) Next I tried two "D" cell batteries in series while also in parallell with one 6-volt lantern battery. The clock has been running and charging nicely for about 30 minutes. I believe this creates a total of 6-volts and by having the "D" cells in parallell with the lantern battery it generates additional amperage.

    First question, how can an electrical novice armed with a simple Radio Shack volt meter determine how many amps I am putting to the magnets? I would assume the section of the volt meter dial labeled mA's is the answer?

    Second question, using commonly available household batteries what do you recommend using? Especially since one of my "D" cell batteries just exploded :o, I assume this is not the recommended sequence.

    Third question, my clock was in a terrible state when I acquired it. Other than the coils, there was no wiring present. I have some original style cloth covered wiring, but need to know where to use it to attach the coil of the slave clock to the movement itself. If you could point me in the right direction it would be appreciated.

    Thank you again for all of your assistance. This is such a neat and different clock than the typical one I get to work on. While it was only running about a half hour, it was very rewarding to here it trigger every 30 seconds.

    Michael

  5. #5

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Michael,

    First, one should never put two battery stacks together at different voltages. I guess you found that out. You've probably ruined your 6 volt lantern battery as well, and you might consider replacing it.

    If your Radio Shack meter can measure the resistance of the coils, you can then calculate the current by taking the voltage (eg a fresh lantern battery is 6 volts) and divide that by the resistance of the coil you measured.

    Your welcome to contact me at ken@kensclockclinic.com if you want to go through some examples or explanations, or other ways of measuring the current.

    Ken

  6. #6

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Michael, Yep, don't put a 3 Volts and 6 Volts battery in parrallel.

    As you found out the 6 Volts battery was trying to charge up the 3 Volts battery and a large current would have flown between the batteries until one blew up.

    It should have done no damage to your masterclock though.

    If you have a multimeter you probably have a mA and a Amp range on it.
    If you are experimenting and not sure what amps are flowing in the circuit, use the Amps range first. This has an internal fuse in it rated at 10 Amps.
    The mA range is usually fused at 300 mA or 0.5 Amps.

    You are on the right track by using D cells which are 1.5 Volts each.
    If at 3 Volts the clock didn't run properly or the magnet didn't pull in then put an extra D cell in series to make the Voltage 4.5 Volts.

    Easiest is to get a 3 or 4 way D cell holder from an electronics shop.

    The ammeter goes in series with the circuit.

    So: ( POSITIVE from batt. ) to ( AMPS terminal on meter ) to ( Common terminal on meter ) to ( Master clock circuit in ) to ( Masterclock cct out ) to ( NEGATIVE from battery ).

    A D cell battery can give a current of more 10 Amps for a short time, the cell will heat up rapidly as it's internal resistance increases, It also will be exhausted very quickly.

    Because the clocks only take around 220 mA for a very short time, a set of 3 D cells should last for a reasonable amount of time.

    Raymond

  7. #7
    Technical Admin Tom McIntyre's Avatar
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    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    It may be difficult to see the current with an ordinary ammeter. It is an irregular pulse from the contact closings. You are better off calculating as shown in the earlier posts.


    misspelled contact:o
    [edit=19=1177816447][/edit]
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  8. #8
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    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    [quote=Tom]It may be difficult to see the current with an ordinary ammeter. It is an irregular pulse from the contact closings. You are better off calculating as shown in the earlier posts.


    In the good old times the Gent engineers put a penny coin between the contacts of the master clock to keep the circuit closed when measuring the current.

    Interested in my electric clocks?
    www.vrolijk-clocks.nl

  9. #9

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Thank you all for your quick and thorough replies.

    I am off to purchase some new batteries and will continue experimenting soon.

    Thanks again,

    Michael

  10. #10
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    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    The resistance of the coils is undoubtedly the primary source of impedance with the low frequency operations. However, these are coils and the dc impedance is not the same as the active impedance in operation.

    There is also a fairly significant breakdown surge that causes most of the pitting on the contacts of these clocks. I tried putting a shunt diode on my Synchronome, but I could not tell much difference. I don't have an oscilloscope anymore to look at these things.
    Tom McIntyre Click me.
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  11. #11

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Good Evening,

    I just downloaded a copy of the Gent's of Leicester installation and repair manual. It contains a wealth of information and now that I have a much better understanding of Volts, Amps, Resistance, etc. it makes sense.

    According to the manual, the master clock movement (that drives the pendulum) has a resistance of 33 ohms. In addition, the slave unit has a resistance of 4 ohms (which is consistent with Rodalco's post). Therefore it appears that my clock has a total resistance of 37 ohms which combined the required current of .22 amperes equates to a voltage requirement of 8.14 volts. This sounds about right as it was operating (weakly, but operating) on a 6-volt lantern yesterday.

    All that said, I am still struggling on where to install the slave clock wires. As the slave clock operates at only 4 ohms, I assume I will have to install the appropriate resistor so I do not burn out the coil. But where to connect the two leads remains a mystery.

    Any guidance would be appreciated.

    Thanks again,

    Michael

  12. #12

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    On the vibrating and rotary motor SWCC models, the inductance (AC impedance of the coil) actually comes into play somewhat. The "time constant" of these coils is on the order of about 20 milliseconds (ms) or less. The motors apply current to the motor for a period somewhat longer than this every cycle, so this AC impedance therefore lowers the current a little vs. what you'd expect from the DC measurement of resistance alone.

    On the single shot self winders (eg once per second or once per minute), the coil is turned on for significantly longer, on the order of 150ms, possibly up to 500ms or more. In this case the AC impedance plays a much smaller role in determining the current and the DC dominates.

    This AC impedance is one of the reasons to avoid using diodes across the coils in the vibrating and rotary motors (stick with the damping resistors). The diode will cause the coil to hold its magnetic field longer than it should after the commutator opens the circuit, which may keep it from operating at its optimum.

    Ken

  13. #13

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    I had a look on Google for you too, but unable to find an exact schematic which details the Gents wiring loom.

    I'm pretty sure the slave dial does go in series with the 30 seconds contact.
    Perhaps someone with a working Gents masterclock can trace the wiring and provide you with a drawing.
    I haven't got a Gents masterclock at home, but a Favag, BŁrk, Moser Baer, Inducta and ECS. which all use the 24 Volts alternating polarity one minute impulse system as used in continental Europe.

    An interesting link though regarding gents clocks is attached below.

    http://west-penwith.org.uk/misc/gent.htm

    Good luck and keep us posted when it all works.

    Raymond

  14. #14
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    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    HI Lincolnhill,
    I have been following this thread for the past couple of days

    This is the easy way to sent up your clock

    I suggest you use a 9 or 12 volt DC plug pack style power supply
    Make sure it is rated at 1 amp or higher.
    3 amps is better because you will probably want to add extra slave clocks later

    You should not need to buy any resistors

    Inside you clock case is a large wire wound resistor (normally on the left)
    It is an oblong shaped item, light grey in colour
    It has a black knob on it with a small silver locking screw in the middle.
    You need to loosen this screw to allow the knob to move

    The wiring is very simple

    The positive (+) of the supply goes to one side of the contacts in the master clock
    The other contact goes to the master clock coil, then to the fist slave then the next and so on in a daisy chain formation.
    The last wire coming from the last slave goes to the negative (-) of the power supply

    This type of wiring is called series wiring and is simply a circle coming out of the power supply, going through all the clocks and back in to the supply

    After you have wired all this up, set your meter to milliamps and put the two probes between the two contacts on the master clock

    The contacts will try to close but you must force them open (a second pair of hand is always useful)
    Adjust the sliding resistor on the left up or down until you get a reading of .22 amps (220 milliamps)

    If you use a 12 volt supply the resistor knob should be near the bottom

    Once you have set this resistor hand tighten the little screw in the knob ane the clock is set.

    You will not burn out any coils with just 12 volts DC

    Before you invest in a power supply you may want to test it with a car battery

    If you are still stuck send me the clock serial number and I will dig out the circuit diagram for it

    Hope this helps

    Edd

  15. #15

    Default Re: Correct Voltage for Gents Pulsynetic Master Clock (By: Lincolnhill)

    Good Evening Ed,

    Eureka! It is now so obvious.

    As I mentioned earlier, my clock was missing all of the wiring when I acquired it. The part you describe, the large grey wire wound resistor is no longer present. I had not missed it because I did not know it should have existed.

    That said, your description of wiring the slave and master clock in sequence is extremely helpful. I had been wondering where on the movement the slave was to attach, but as you describe it attaches within the power supply circuit and not the movement itself.

    OK - Here is where I am at:

    1) The clock is running and "winding" nicely on 4 "D" cell batteries set in series and therefore producing 6 volts. It will not wind on 3 "D" cell batteries or 4.5 volts. According to my calculation and the information in the users manual, the gravity coils draw 33 ohms which when combined with a 18 to 22 mA resistance should require 5.94 to 7.26 volts. So my 6 volts seems both reasonable and not too high as to damage the coils.

    2) I then acquired a generic 10 ohm, 10 watt ceramic resistor from Radio Shack. When installed in series with the 6 volt battery pack the slave clock advances nicely. Not too powerful, not too little. If I install two resistors in series then I get nothing.

    As my clock is missing the adjustable resistor Ed describes, I am going to try everything in series with no resistor and see what happens. Will keep you all posted.

    Again, the good news is that everything is ticking merily and seems to be reseting the gravity arm properly. I adjusted all of the tolerances back to factory specs last night and the gravity arm triggers much better than a day ago. I think we are getting there!

    Michael

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