Instead of forcing the pendulum to synchronise with an electronic timebase by accelerating and decelerating using electromagnets, how about this idea: Have the bob shift up or down along a worm screw driven by a small motor. If the pendulum oscillates to fast, lower the weight, if too slow then you raise it.

 

Cabwood

Thanks for your idea, very good thought but not really practical.
A pendulum clock is in general very accurate, if a minor adjustment is needed the course adjusting screw may have to be turned 1/16 of a revolution, or the fine adjustment screw 1/32th.

On heavy bobs a small weight ( 1/2 gramme ) may be added for a period of time or removed.
We talk bobs between 1 and 10 kg.

A small motor with it's associated wiring would cause bigger errors in pendulum accuracy because of microns of endplay in its armature shaft between different activations.
Also the controlwiring will fail at some stage due to repetitive flexing.

Thanks, Raymond

__________________
There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

Have you seen this one? It seems to infer the kinetic art toys I referred to earlier use the same idea... I may pick one up at the local dollar store just to open it up...

I'm thinking of incorporating a decent sized relay (open frame for good aesthetic measure) that will be synced with the impulse circuit (or other pendulum counting sensor) to get the audible 'tick-tock'.

I also woke up this morning with another clock face idea based on the old color-changing Aurora Clocks from the 70's... Honestly, I should probably see a therapist

Thanks for the info on the suspension spring.

 

The Solarbotics.com "SunSwinger Pendulum Kit" adds a transistor and uses a single coil for sensing and pulsing. You can download the manual which has a schematic diagram of the circuit.

 

Thanks agent 420 and bobledoux for your links.
They could be useable, especially when a external crystal oscillator is used.

Here are a couple of pics taken from the Hipp Toggle mechanism in my Favag 2/3sec masterclock.

http://farm1.static.flickr.com/242/4...75faebeb65.jpg Hipp toggle coil

http://farm1.static.flickr.com/237/4...5206c6a76b.jpg Hipp toggle coil

http://farm1.static.flickr.com/242/4...6ea363324f.jpg Hipp toggle switch

http://farm1.static.flickr.com/175/4...9a5e3c900d.jpg Hipp toggle switch

Regards, Raymond

__________________
There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

I have a room full of cuckoo clocks, I had to sound proof the room so it didn't drive my wife crazy. 125 clocks all going off at once is a great sound to me.
sam

 

I'd like to avoid any electronic timebase in my project. While I'm sure that such a circuit would no doubt improve the accuracy of the clock, there is just something about a 'natural' timebase that appeals to me. Occasional time (re)setting is just another reason to go play with it LOL. I will however try to make pendulum assembly fairly accurate, probably using invar. I'd love a merc compensated pendulum - how many old thermostats do I need?

I am quite jealous of your Favag

Music to my ears as well. I sometimes play the intro to Pink Floyd's Time just for that effect

Although it started as a side project, I am thinking of incorporating my solenoid driven xylophone (similar to the Xylotron III) into the clock to serve as a chiming mechanism.

edit -

I note the polarity of the impulse in the referenced schematics that repel the pendulum is opposite in comparison to the older mechanical designs that attract the pendulum. It seems to me that the repelling method may introduce error because the lines of force are probably not always the same, as well as they won't always be tangent to the pendulum arc. I would think the attraction method is better in that respect...

 

Ray

Nice neat set up.Probably close to where I want to be with the electromagnets below the pendulum.The hip and toggle set up must have to be at critical points in relation to the pendulum??? I suppose basically this works when the pendulum tiers enough for the little toggle to engage with the V slot thus causing a circuit .So no electronics required to impulse the magnets!!!

I think I would like to take this further and use combined electronics and Mechanics.The Mechanics being the pendulum and the electronics being what keeps the pendulum swinging.I think I would like to go down the route of placing a Permanent Magnet below the pendulum and use a sensor and a PIC. do do the maths.

Anyone with any ideas of sensing and creating a circuit usng PIC's to see where the pendulum is at and what it requires to keep it running I would like to hear your comments.Please try and explain in Layman's terms just until I learn the Electro Jargen!!

By using PIC'S to control the pendulum and because the pic should always know where the pendulum is and at what rate it should be swinging at I.E 1 beat per second We should be able to produce a slave contact from the circuitry.


Any help will be very appreciated.


Regards Mark

 

My physics is a bit rusty, but I'm wondering how a microcontroller or other 'smart' impulse method affects the pendulum accuracy... If I understand correctly, a pendulum has a natural oscillation, and it's period is not necessarily related to the length of swing in the arc, but only the length of the pendulum itself.... Meanining that as the pendulum 'slows down' or swings less side to side, it still takes the same amount of time to complete a cycle.

For a one second pendulum, that equates to approximately 39" (link)

 

Agent420

I see what you are saying about the pendulum and you are correct with the length of the pendulum and the arc being fundamental to accuracy but what I think I'm trying to say is-

If we are using a 39" 1 sec beat pendulum we still need to give an impulse to keep the motion going while this is a simple operation as in hip/toggle movements where the pendulum receives an impulse via contacts as the length of the swing decreases and this is as you rightly said not an arc issue but a continuous motion issue but still the impulse is at a given rate.

I think when using Electronic impulsing Mathematics have to take over.We can use the fact we require an impulse no matter what and we can use this fact to impulse at set points. I think these points have to have a source from which information is gathered and this would be the pendulum.While we cannot use the electronics to control the pendulums rate (this is best left to the rating nut) we can determine when impulse is required.

PIC'S and circuitry could take over what the contact set did for hipp/toggle clocks but we keep the Electromagnets. The PIC may as well be used to it's potential being used to calculate the pendulums position we can then use these calculations to run off slave indicators.

Basically the Pic would be the clocks motion work as in std Mechanical clocks and motion work only works with the correct gearing on the wheels together with pendulum length and constant motion and would replace contact set as in Hipp/Toggle clocks.

Having said all this this is only theory, practicalities may be another issue. I am not an expert in electronics and my explanation is only vision. I would very much welcome suggestions other than Pic's to do the job.

Regards Mark

 

agent420 Interesting link re the maths for a pendulum.

I knew the 2 * Pi * SqRt( L/G) formula which works out as near 1 metre for a clock with a one second beat.

markelectro

Better to have the pendulum rod a little longer than one metre than too short.
The distance is measured from the suspension spring to about halfway in the pendulum bob. I would go for a 1.10 metre Invar rod with enough thread at the end to allowe for fine adjustment.

The Hipp Toggle works on the attraction method and is very simple and minimises interference with the pendulum.
It only closes the contact when the pendulum arc decreases enough to engage the v shaped pawl, to fall in the v shaped notch and close the contact briefly, energise the coils, attract the pendulum and keep it going for the next 20 swings or so.

The Favag minute wheel rotates every 2 minutes, has 2 contact pins, one for positive impulse, one for negative impulse, for a full turn and is driven via a ratchet system from the top of the pendulum rod. I can take a few more photo's if you are interested.
The Favag is designed for the European master slave clock systems, which usually run on 12 or 24 volts dc, with 1 minute impulses, and changing polarity every minute.
My Favag runs within ± 2 seconds per week, which is very accurate.
A solid wall is important too for mounting a masterclock, and not exposed in direct sunlight to avoid excessive temperature changes.

The French Electrique Brillié system uses the alternating polarity system with changing polarity every 30 seconds, for a 1.5 Volts dc supply to the clocks.

In case of the English 30 seconds single impulse slave clocks the minute wheel may be a 30 seconds wheel with 15 cogs and 1 contact pin, or a one minute wheel with 30 cogs and 2 contact pins.

I have a Favag booklet somewhere in my archives and see if can find exact distances are for the position of the Hipp Toggle in comparison to the pendulum rod.
For the 2/3 seconds beat i can measure it for you, but you are designing it for a one seconds beat, so i assume it will be within proportion, distance wise.

If you are in the building stage and get excessive swing you can always reduce the voltage applied to the driving coil by inserting a resistance in series.

Regards, Raymond

__________________
There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

A good little book to get is :

Electric Clocks and how to make them.
From F. Hope - Jones
ISBN 0 85242 533 3
From Argus Books
14 St James Road, Watford, Herts, England.

I bought it on Ebay USA for US$ 10.

It discusses the Synchronome system in detail, as well as various clocks based upon the Hipp Toggle system.

__________________
There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

Ray
do Argus have a website.I would like this book.

Regards Mark

 

http://cgi.ebay.com/How-to-Make-an-E...QQcmdZViewItem

I bought it from this seller Chez Willy.

The book i mentioned is not for sale at the moment, although i bought this book too which is also very detailed in electric clock building.

Regards, Raymond

__________________
There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

I've been putting thought into this as well. The coil triggering method is dependant on the speed of the pendulum as it passes the coil; greater speed results in a higher voltage pulse and vice versa. As any of these cirucits are basically a comparator, triggering the impulse when a set voltage is reached, it is not enitrely location dependant; the pendulum speed will affect the trigger.

Mechanical triggering may be more accurate in this respect, but then you have contact issues and the physical interaction of the pendulum and the switch... Still that system can work with high accuracy as commented by RODALCO about his Favag. More importantly, this shows how accurate a relatively 'simple' system could be, a fact that I think should not be underestimated.

I have been thinking about using a sensitive Hall-effect sensor set for bottom dead center as the trigger. It should be location dependant only and not impart any physical interaction with the pendulum...

Basically what you would be doing is simply calculating a delay time for when to start the impulse, based on the location trigger referred above. This would not necessarily have to a complex circuit, but it should be accurate and repeatable. Some delay time is always going to be required, as you will not want to send the impulse until after the pendulum has passed BDC.

I think a sensor is a better indicator of position that attempting to calculate the pendulkum position. There are too many variables involved. The pic could calculate the required delay, however. You could also measure the pendulum accuracy by comparing measured triggers to a known higher reference, such the PIC's quartz oscillator. This information could then potentially be used in calculating the required impulse delay.