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How can you "drive" a wind clock?

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Eugene:
Some years ago at the National Trust property, Coleton Fishacre, along with some interior decorating and garden design ideas which we pinched, I saw my first ever wind clock and decided one day I'd make one. Next year I'm doing a major refurb. on the snug in our cottage and this will be my big chance.

Here is a snap of it in the library ....



How cool is that?

Superimposed on a painted map of the coast where the house sits is a dial showing the wind direction. The wind vane on the roof is connected mechanically to the compass dial indicator; I think its steel rods and bevel gears running down the inside of the chimney but I'm not too sure after all this time. Anyway that's not for us, we want some form a device that attached to an exterior wind vane can "drive" the compass needle with a bit of damping. I guess this means some sort of electric signal transmitted to "the driver" but I'm clueless on electronics.

So there you go fellers, what can you come up with that an electrical duffer might be able to cobble together, or indeed can you see any other method?

Thanks

Eug

awemawson:
That's what synchros  and resolvers were designed for. WW2 technology but they work!

Bluechip:

--- Quote from: awemawson on August 20, 2014, 06:08:06 PM ---That's what synchros  and resolvers were designed for. WW2 technology but they work!

--- End quote ---

Very true, Andrew. Remember those from work a long time ago. Not seen them in Poundland recently though ...  :lol:

OK Eugene ... There was a Weather Station in Practical Electronics [ I think ] round about 1980-ish which had one.

It would be easy to implement one now with a Gray code transmitter disc [ IIRC it was 5-bit giving 16 points ] and a uController / stepper for the display wotsit but that's not much good for an ' electrical duffer' though ...

If you wanted use 2 uControllers, one at the top end to send serial data to t'other. Cuts down on the cabling  ... make it as complicated as you like ..

One here with LEDs :

http://www.instructables.com/id/LED-wind-indicator/

I can't think of any really simple electrical way to do it other than hurl vast sums of money at it with S/R set up.



Bit of a bugger ain't it ???


Dave

vtsteam:
Maybe an R/C servo, and a servo tester.  You'll have to open them and maybe play with limits contacts to get 360 degrees of movement. Same with the pot in the servo tester.

Try Hobbyking for low prices. Make the servo a big one, not for power, but so it's easier to work on.

Maybe Simon Heslop can help you out, now he's familiar with servo testers in his electric bike build.

R/C sailboat winch servos might allow 360 degree movement out o the box, not sure.

Anyway this would potentially be a very cheap system, though requiring tinkering a little to get full movement.


or.......... maybe a scrapped antenna rotator?


ps. could drive you a little nutty in gusty conditions? Might want to think about something that does averaging, well damped.


re. synchro motors -- Andrew, Bluechip, would old electric clock or other synchronous motors be able to be convinced into a pair, or is the word "synchronous" not really applicable to synchro motor pairs? Or what about stepper motors -- can they be fooled into thinking they are synchros?

John Hill:
The required  'synchros' are magslips and quite different to any regular synchronous motor, they are also quite different to what model aircraft folks know as servos.

I have some idea of how they work and I have a few in the shed (but that is in New Zealand!).

This is Madmodders and we should be able to design and make our own! :lol:

Anyway, this is how they work:  There are two devices that are similar  motor like devices which have a three phase field and a single phase on the armature.  Both ends are the same,  the three phases at one end are connected via 3 wires to the three phases at the other end.  Both armatures are connected to an AC current.

The AC current in the armatures induces  AC currents in the field windings phased according to the position of the armature.  If they are free to move the two armatures will take up a position were the 3 phases at one end are in phase with the 3 phases at the other end.  Therefore if you move one and the other is free to move it too will move the same amount.

Now then,  Madmodder hat on!   :coffee:
A common or garden car alternator has a 3 phase stator and a single phase armature.  In the alternator the armature is called the field.  At first glance it would appear that two alternators could be used as a magslip link and drive the wind direction device.

Not really electronics,  more electrics.

So,  how to test the idea.  Get two alternators that are similar.  Get a low voltage AC transformer,  those 12 volt lighting transformers might be good enough.

Open the alternators and snip out the diode bridge  so that you have 6 wires coming from the stator windings.  Use you meter to identify  the ends that are connected to each coil then connect all three coils together in series, there will be 3 joins required and these joins are the 3 phase connections that you connect to the similar 3 phase points on the other alternator.

Get rid of the voltage regulator if it is internal and find the two wires that are connected to the rotor via carbon brushes (these will likely be labelled 'F' for field),  connect the two rotors together in series and connect to your 12 volt transformer along with a 12 volt light socket all in series.   

THAT'S  IT!

Put a 12 volt globe in the light socket and turn on the power to your 12 volt transformer.  Hopefully there will be a bit of buzzing and the light will be lit but not full brilliance.  Turn one shaft and see if the other one moves, or at least shows any tendency to move.

Report your results.


BTW,  these devices were invented in WWI and used in battleship range finders and gun control equipment.  They wanted very low friction and maximum sensitivity and resolution so did away with the troublesome slip rings and brushes and replaced them with magnetic connections which they called magnetic slip rings, hence the name 'magslip'.  They are called 'synchros' in the US.

There are a couple of reasons why this idea might not work and one of them is that the alternator may have too many poles, but I dont really know so hopefully some keen type will try the above experiment!

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