# Levitating Motor



## Ken I (May 22, 2012)

This is my current project - one of those magnetically levitated Mendocino motors.

This is just the PoC lash up which ticks over at about 60 rpm on my bar in ambient light or at night time under one of the 20W mini downlighters - which is just what I was hoping for.







Along with some of my other engines on the bar.






I foolishly tried to get it to levitate horizontally but according to Earnshaw's theorem Maxwell's equations prohibit this.

(There are some loopholes to be explored yet - I actually want to build a verticaly levitating version but unlikely without some supporting electronics.)

As per usual I will post a full set of plans and build notes under the downloads section once completed.

Watch this space.

Ken


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## b.lindsey (May 22, 2012)

Very cool Ken ! Any chance of a short video of it running ? Quite a nice collection there too...must make for some interesting bar chat 

Regards,
Bill


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## lazylathe (May 22, 2012)

Sweet!!!!

I have been looking at those for quite some time now!
The commercial ones cost around $200!!

They look like an interesting item to build!

Thanks for posting the plans when you get a chance!!

Andrew


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## Herbiev (May 22, 2012)

Great project Ken. IIRC Earnshaws theorum dates around 1840 before superconductors came about so there are indeed loopholes to be explored.


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## Don1966 (May 22, 2012)

Great project Ken, I have seen these before. College students build those for classes. Been wanting to build one myself. It makes a good conversation piece. Ihave a small version but no photo cell on it, when you touch it LEDs light up on it. 

Don


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## hitandmissman (May 22, 2012)

Will look forward to those plans. If I had a bar like that I would never get anything done. I mean watching the engines run of course, lol.


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## Ken I (May 23, 2012)

Bill, I will probably only make the video when completed - but if anything interesting pops up or I get a chance I might do one sooner.

Herbie, Even superconduction magnets and very powerful fields are restricted by Earnshaw's theorem - what he did not consider was the diamagnetic properties of most non-magnetic (as opposed to paramagnetic) materials.

Diamagnetics oppose a magnetic field - regardless of polarity - but the effect is very weak and only becomes significant in very powerful fields.

The strongest diamagnetics are Bismuth and Pyrolytic Carbon which offer sufficient force to levitate a small magnet within the field of a larger neodium (NBI) magnet.

Even water (and your own body) has diamagnetic properties - they have been able to levitate frogs and mice in extreme magnetic fields using this effect.

I have been trying to get hold of Bismuth - but I get the look reserved for AlQada members looking for Plutonium.

In the US they use the stuff for birdshot - its non-toxic compared to lead - I'm sure the birds really appreciate that.

Ken


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## mu38&Bg# (May 23, 2012)

Very nice!

Is this the effect you want to achieve?

Greg


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## Herbiev (May 23, 2012)

Ken. You are correct in regards to the diamagnetics which have a relative permeability of less than one. (i.e negative magnetic susceptability). I have experimented with bismuth which did indeed come from birdshot. I mention superconductors as they can be considered as the perfect diamagnet with relative permeability of zero and can completely expel magnetic fields due to the Meissner effect (discovered early 1930s) when the superconductivity initially forms. Further stability is accomplished due to flux pinning within the superconductor. 
I have also achieved levitation using a number of Hall effect devices but that is another story.


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## Ken I (May 23, 2012)

Greg, Thanks for the link - yes - but I'm not sure I can support the mass of the rotor but I'm going to try.

Herbie, You know your stuff - my crystal ball tells me you are likely to recieve a PM from a confused stranger with issues.

Regards,
      Ken


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## mu38&Bg# (May 23, 2012)

Ken, I'm not sure I understand the concern then. Those pens just use a magnet in the top to keep it standing. I had one as a child and it spun like crazy. The closer you put the magnet to the top the less load there will be on the contact point on the bottom. As long as balance is not atrocious I expect it will work just fine.

Greg


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## Sshire (May 23, 2012)

Found this. I want to build it.
http://www.bis0uhr.de/index.htm?htt...LzZX0i5qnijxPI8Kw&sig2=8_RNzRFyrj6kA-orThZG5g

Best 
Stan


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## doubletop (May 23, 2012)

Now we're all watching............


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## tel (May 23, 2012)

... including me! ;D


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## jerrybilt (May 23, 2012)

Hi Ken,

Good work there! I like it. I have never seen one of these motors before and this looks really interesting. I'd be very interested in your plans. What is the source of those magnets?

First take on the motor:

It has two windings to create a rotating magnetic field (two fields in phase quadrature) ... commutation is via the solar cells rotating away from the light source and the fields.

Question: Adding an additional pair of windings and solar cell pairs will smooth the torque but will this work without major modifications to your design?

Jerry.


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## lazylathe (May 23, 2012)

Found this link:

http://www.mendocinomotor.de/motors-and-kits/1,000000562895,8,1

Some with 6 solar cells and a vertical one!!

Andrew


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## dgjessing (May 23, 2012)

I want to make one!


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## Herbiev (May 24, 2012)

I want to make one too. These motors have certainly generated a lot of interest but having four projects under various stages of construction I feel I should complete at least one of them before making a start on one of these fascinating little devices.


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## Ken I (May 24, 2012)

Seems like a lot of interest.

Greg - I wanted to levitate it vertically not just "hang" it off a magnet - but that will do (I actually want to build two, one horizontal and one vertical - possibly combined - just swop the rotor. 

Stan - that's an excellent link and anyone interested should look it up. I agree with their magnet configuration - with like poles facing out so it doens't matter which way around you place the rotor.

Andrew, Jerry - you can have any number of poles but 4 is the easiest - odd numbers requre connection in star or delta.

Now for a bit of practical info:

Firstly none of this is complicated or requires any exacting fabrication - almost anything can be made to work.

I scrounged the solar cells off some dead Chinese pathway illuminators (garden lights) - these cheapies tend to die within a year and are then discarded - so keep your eyes open.

The actual cell is a QHDQ-08A - which is a 50mm x 50mm x 2mm thick solar cell - probably the most commonly used cell on this type of application.

They're rated at 100mA @ 3V - In direct sunlight in Cape Town the best I could get was 68mA @ 2.7V - so I'm guessing that rating applies at the equator with the sun directly overhead.

You need high current / low voltage for this application - higher voltages will require more turns of thinner wire.

I connect each cell pair in paralell - you could do it in series - but you'd just be making work for yourself. Opposite pairs are connected together in reverse and on to the coil - simple.

The magnets I bought - just look up a magnet supplier - they are not terribly expensive.

I used a 25 Diameter x 7 Diameter x 6 thick. (Neodium, Iron, Boron) - this is a standard size - obviously the hole in the middle simplifies mounting - also since these things are sintered - the sizes are quite precise.

Be careful these things are powerful enough to inflict a nasty pinch and can fly together so violently they shatter (in pairs) I've broken two and my grandson 4.

(I use some 50x50x15 magnets on industrial applications and they are seriously dangerous.)

My rotor hub is made from 6mm MDF and tongue depressors - somewhat incongruous machining a lollipop stick in a mill but WTH.

I placed the bits of wood in the MDF grooves and secured by pressing drill shanks into the slot to hold in place - then applied superglue to all the joints to secure (being careful not to glue the drill shanks in place) - after winding, a coat of Glyptal secures the winding and everything else together.

The shaft is a diameter 7 x diameter 5 carbon fibre tube from a hobby shop and the spacers are Dia 10 x Dia. 7 aluminium tube.

Winding wire is 36 swg (0.18mm) ± 150 turns = 40m.

Again I "scrounge" my winding wire from rewinders and transformer manufacturers who consistently throw away near empty spools - still plenty of wire on them but not enough to bother with the next "run".

So if you are interested - you might start looking for scroungable materials.

The height at which the rotor levitates is obviously determined by the position of the magnets and the mass of the rotor - hence my lash up - the final centre height will only be determined once the rotor is finished.

Ballance is an issue - static ballance is dead easy - but it really needs to be dynamically ballanced as well - without using sensors etc. I am doing mine (not finished yet) by sticking lumps of modelling clay to the rotor - static - then with a piece of tape wrapped to the rotor shaft I bring a magic marker to make a mark at the high point of the "wobble" - add a small clay mass (a guess) to counter it (removing the piece from the static lump) - once I get that right I will replace the clay with bits of copper wire bonded into the winding grooves. Final touch up ballancing will be by adding epoxy or laquer.
The other reason ballance is a bit fiddly is the "centre" is the magnetic centre - so bond the end magnets in place before final ballance tuning (if you move them angularly after ballancing you can throw the ballance out slightly).

I did the winding in my 4 jaw (turning by hand - gearbox in neutral - a PITB) with alternate layers going to opposite sides of the shaft - I used glass tape over the shaft spacers and between crossover layers for added insulation (given the low voltage this is probably overkill but WTH). I wound half of each winding then changed to the other to ensure a more even crossover.
The crossover obviously ends up with a lot of voids which I filled with a hard (very quick setting) polyurethane resin - but any quickset epoxy or polyester would do the trick.

Hope to get more done over the weekend.

I'm going to make the base and support structure out of perspex (to enhance the open appearance). I'm going to replace the brass acorn nuts with perspex end extensions with a steel ball in the end - this will run against a glass plate - I might put a small magnet behind the glass to secure against collywobbles from imperfect dynamic ballancing / higher revolutions.
I intend to put supports at both ends to gaurd aginst rubberneckkers knocking it off.

The rotor should just float on the magnets with a slight bias towards the support end (only one) with two it will move to one or the other end (who cares).

I have made a few glass disks with a 30mm diameter diamond tube drill - but the edges look like they were made by a neolithic flint knapper - does anyone have tips on how to do this splinter free ?

Ken


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## rhitee93 (May 24, 2012)

Ken,

I am loving this engine idea. My chosen profession is an electrical engineer, but it is rare that I allow any EE work into my chosen hobbies. (I like my work, but I also like to leave it at work) however, this is one that will cause me to cross-bread a bit.

How thick do you need your disks? I bet I could cut them on the waterjet here. I'd cut them for the heck of it, but shipping to Cape Town might be prohibitive.


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## Ken I (May 24, 2012)

rhitee93  said:
			
		

> I bet I could cut them on the waterjet here. I'd cut them for the heck of it, but shipping to Cape Town might be prohibitive.



Thanks for the offer and a great big slap upside my head - I know plenty of customers with waterjet who might oblige - why didn't I think of that.

Ken


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## rhitee93 (May 24, 2012)

Cutting glass is a bit tricky on one. The piercing tends to cause a lot of chipping on the surface so you have to use a long lead in before you get to the cut line so the chipping doesn't end up on your part. 

Optionally, you can start the jet off the edge of the glass and move into the material with the abrasive flowing. That works well, but requires creative programming.

You can also by 30mm disks here http://www.edmundoptics.com/


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## Herbiev (May 24, 2012)

Ken. One KP for the brilliant "scrounging" ideas. Being on a part pension here in Oz really restricts the money available to the hobby. Little freebie tips like these really do stretch the dollar. Love to hear any other tips from members :bow:


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## Ken I (May 26, 2012)

Progress.....

I have extended the shafts and I'm working on the base, in the meantime I have a few observations - maybe a member can chime in with some enlightenment.

The motor seems to run better in one direction - if you turn the rotor around it still goes the same way but one way arround is beter than the other. Doesn't make any sense.

I reversed the field magnet - which reverses the motor - still the same - here there is also a difference which I suspect is constructive / destructive interference with the levitating poles.
That does make sense. But the difference on reversing the rotor remains.

The output from the photocells seems to be temperature dependent, they seem to give more output warm.

Windings - I was interrupted and lost count during winding - as a consequence my 2 windings are not the same (37 vs 45 Ohms) - this gives the motor the collywobbles - unrelated to ballance - due to uneven thrusting by the windings - Lesson - make sure you count the number of turns accurately - I'm going to rig up a counter if and when I redo it. I don't see how the uneven winding has anything to do with the difference in performance when the rotor is turned around.

I have run it up to 200 rpm under a 50W downlighter the collywobbles settle down - I guess in direct sunlight its going to get to about 1000 rpm.

Contamination - Iron filings (our shops are full of them) getting into the laquer, pressed into or even in the MDF also cause ballance-like issues.

The finished rotor weighs 241g and from a ballance point of view is sensetive to 0.01g, - I can measure to only 0.1g and using modeling clay a fraction of this induces it to turn - statically.

I'm still fiddling with the ballance issues - again some curious observations - I'm getting different results with the field magnet in or out (if you ballance with the magnet in - it wants to rotate under the bench lights - a winding disconnect point might have been a good idea) - here I suspect contamination but I'll be damned if I can find it.


Ken


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## steamer (May 26, 2012)

You never cease to amaze me Ken!  That's cool!

Dave


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## Ken I (May 26, 2012)

Well here it is almost finished (apart from a bit of polishing) I managed the glass disks by sandwiching the glass see..

http://www.homemodelenginemachinist.com/index.php?topic=18793.msg194667#msg194667

Here it is running on the bar at 20 rpm under a 20W downlighter







the blur is because of the camera / low light level.

Here it is stopped.






I used stops at both ends to prevent das dumpfkoppenrubbernekkenundsightseeren from knocking it out of the cradle - it runs fine with only one. 

And a video of it running.

http://www.youtube.com/my_videos_edit?ns=1&feature=vm&video_id=fplVwOuAv38

The speed it was turning (when I grabbed it) was the stable speed it was running at the time.


The speed has been going down as ambient light levels dropped (I hope that's why its been slowing down) and its now dark outside and ticking over at a turgid 15 rpm which is nice as a conversation piece for the bar.

At this speed its not self starting which I suspect is a ballance issue - the torque is so very low - with a brighter light it self starts.

I haven't tried it in direct sunlight yet it will probably go ape.

Give me a couple of days to tidy up the drawings & build notes and I will post it under the downloads section.

Ken

Edit - P.S. Apart from this project I have been desinging and building some powerful magnetic grippers for robotic use.

These powerful magnets are a curse - everything that comes in contact becomes magnetic (yeah sure - I'll demagnetize them later), they can jump together violently enough to shatter against each other - and really big magnets can do some serious damage to your digits if they get in between a pair.

Tools leap off the bench to attack you or whatever it is you are working on - my normally docile scriber leapt off the bench and impaled itself in my finger. In a jealous rage my pliers took a snap at my project.

My advice - clear the workspace and keep it as clear as possible for the duration (do as I say - not as I do !).


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## doubletop (May 26, 2012)

Ken

This an absolutely wonderful insight into a subject a lot of us probably had no idea about, and like me are now on the lookout for the various components. I'd found the source of neo magnets in NZ only the other week for another application. No doubt there will be a few more of these motors presented here over time.

I now realise that the levitation is bought about by the magnets in the end plates and at the rotor tips and the coils only provide the rotational drive with commutation provide by the ambient light on each of the solar cells. I had thought that the magnets at the rotor tips were bearings and the armature would rise off the stand as the speed increased

I like your use of acrylic to add to the effect of "look no hands, hidden wires or magic". Maybe an acrilic rotor is on the cards? First thought on seeing it was it needs some leds embedded and would some magnets on the rotor with an induction coil in the base. But maybe not.

Dare I say the second end stop does need to be removed it detracts from the effect. However I can see it's there to deal with the effects of Kinderfingerpoken

Nice job 

Pete


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## George_Race (May 26, 2012)

Hi Ken, very nice project description and build. Your final design really does run great!
I have been a fan of these kind of motors for some time, and started putting one together just this week.

Gosh, do you think we can convert this group of engine builders to Mendocino builders?

These little devices are sure fascinating to watch run!


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## Ken I (May 27, 2012)

Pete,
    I've come to the same conclusion - having two end stops detracts from the effect - but I can flip one down by hand easilly enough - I will post another clip of it running with one.

Yes a totally acryllic rotor is possible and would look nice.

My caution to anyone building this is to make the rotor complete and then do a lash up to determine the centre height - it will vary depending on the mass of the rotor and the strength of the magnets etc. etc.

I could have targeted a faster running motor using more turns of thicker wire - but I was deliberately aiming for "slow".

George, thanks I will be following your thread.

Ken


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## Ken I (May 27, 2012)

Here it is running at 50 rpm under ambient lighting (no illumination lights turned on).

The Windhoek Draught is to amuse Arnoldb - and I was thirsty.

This is to show it running with only one support end (as mentioned in prior posts two spoils the effect - but are there because I have grandchildren). The screws are loose enough to manually fold them up or down.

I took it outside in direct sunlight (low angle winter sun) and it spun up to about 1200 rpm before the collywobbles caused the rotor to strike the field magnets (I've only got ±1mm clearance) and it would have run over the fields and far away has I not had my hands in place for such an eventuality.

I think a couple more milimeters clearance would not hurt.

Ah well - it ticks over nice and slowly on my bar - day or night and that was the intention so I'm happy - Calling this project finished (for now).

(Sorry the vid's at the bottom but for some reason if I place it further up the post then everything below it dissapers ?)

Ken


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## Ramon (May 27, 2012)

Ken, 

I have just caught up with this thread and would like to say what a super piece of 'engineering' you have created. 

I confess that to date this sort of project is not exactly my cup of tea prefering I guess those of a much more conventional nature. However, this has simply 'bowled me over' and though I'm not sure I will ever make one your description of the build and the way in which it works certainly makes me 'want to'  I await the drawings etc then with great anticipation - who know's? I/C could go on hold for a bit 

I thought the way you overcome the glass cutting problem was truly brilliant. :bow:

Thanks for sharing it with us - good on you Thm: Thm:

Regards - Ramon


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## doubletop (May 27, 2012)

Ken

Moving the second end stop is just what it needed.

Another question. Do the support magnets adjacent to the end stop need to be slightly lower than the opposite set so the rotor tends to slide down hill towards the stop or is it the effect of the armature and field magnet that pushes it towards the end stop? _(just had a flashback, Lenz's law?)_

Great job

Pete


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## Ken I (May 28, 2012)

Pete,
    The end stop magnets were a bad idea - they're gone.

The idea was by attracting the ball in the end it would stabilise any ballance issues - it didn't work for that purpose.

With them repulsive from the rotor magnet, (it still attracted the ball but very lightly) when you folded one stop down it pushed the rotor off its magnetic perch.

With it in attractive mode (strongly attractive to both ball and rotor magnet) it increaced friction spoiling the ultra slow low light performance and still did nothing for ballance issues at the free end.

It was just one of those experiments along the way that didn't pan out.

So ignore them. (Well spotted by the way.)

With the rotor magnets directly over the support magnets, the rotor is perfectly suspended - but unstable - it will slip from its perch to the left or the right - by placing the end stop about 1mm away the rotor is effectively falling down the magnetic hill towards the stop and is thus stable.

Literally a micron off is stable but a puff of wind can dislodge it, so more offset increaces the force against the stop - none of this is critical - if the distance between the rotor and support magnets is not the same (within reason) there is still a stable point and as long as your stop is just off from that it is fine.

I got the bright idea that I could also suspend this horizontal float with magnets - thus completely levitating the rotor - after a hell of a lot of experiments I dicovered its not possible. Turns out Earnshaw's theorem proved that Maxwell's equations make it imposible to achieve static magnetic levitation in all planes. Bugger.

It could be controlled electronically but that's not really in the spirit of this build.

Like I say build notes to follow - unfortunately my son has broken his collar bone in a mountain bike downhill crash at the weekend and I will have to fill in for him which is going to drastically reduce my hobby time for a few weeks.

Ken


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## Ken I (May 29, 2012)

O.K. for those of you who may be interested I have finished all the documentation and drawings.






I've loaded it in the downloads section as a *.zip file containing the drawings as *.dwg, *.dxf & a single sheet *.pdf plus a *.doc file of the build notes.

Have fun but they'll cost you a KP point - and that's free.

Regards,
        Ken


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## golddustpeak (Jun 1, 2012)

Ken,
Interesting project and a very well done completion.

Just out of interest how did you end up choosing to use a 45 ohm (150 turn) winding?

Neil


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## Ken I (Jun 2, 2012)

golddustpeak  said:
			
		

> Just out of interest how did you end up choosing to use a 45 ohm (150 turn) winding?


By a process of calculation - which I got wrong, guesswork, intuition and dumb luck.

Max. output occurs at matching impeadance ie 3V @ 100mA = 30 Ohms (but I went and calculated 90) for two cells in paralell halved it to 45 - so I got that wrong from the getgo.

Next what gauge of wire - as that will influence the number of turns - clearly more turns improves youre Ampere Turns - but more turns increaces the back emf - so where is the optimum - pretty much anyone's guess given the imperfect field set up of this motor.

Why 36swg ? well it will handle 200mA and I had a roll and that equated to 45 Ohm at 150 turns.

I'm afraid it was a classic case of confirmation bias - I intuited about 150 turns and pretty much found what I was looking for by accepting answers that agreed with that - dumb - and a real problem for serious research - but in this case no harm done.

So ultimately I would have to write it off as a lucky guess.

Ken


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## golddustpeak (Jun 3, 2012)

> Max. output occurs at matching impeadance ie 3V @ 100mA = 30 Ohms (but I went and calculated 90) for two cells in paralell halved it to 45 - so I got that wrong from the getgo.



That's where my confusion came in.
I was figuring 2, 3v 100mA cells in parallel would yield 200mA @ 3v and require about 15 ohms, or even 2, 2.7v 68mA cells in parallel working with 19 ohms.

So with your 45 ohm loaded 3v cells you would be at about 67mA.

I'm going to be using 2, 4.7v 81mA cells in parallel and I am just struggling to decide on a number of turns to use as I've done some research and found no hard and fast rule.

Following your successful example (and other examples I've seen) I'm wondering about using say 75-80 ohms or even more heavily loaded at 58 ohms.

Looking at wire sizes and my choices in the shop I will be using #36 as well, as it seems to have a nice resistance per turn for a project like this. 

Neil


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## gld (Jun 3, 2012)

Tried to download the zip file..All I get is a 53 k file that Windows XP says is corrupted.. ??? 

Gary


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## Ken I (Jun 3, 2012)

I dont know why that happens. :-X
try again tomorrow.
ken


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## gld (Jun 4, 2012)

Ken

Retried on my laptop running Windows Vista and it worked perefect....

Very nice work and Thank You for sharing..it will be a fun project ..1 more Karma added.

Gary


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## Don1966 (Jun 4, 2012)

I had the same problem and had to download it twice. Thanks Ken for sharing.

Don


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## gld (Sep 20, 2012)

Ken

At the point of winding the coils. I'm using #36 wire and shooting for 15 ohms. Your spread sheet shows 106 turns. I wound 100 turns and measured 36.8 ohms. From that I assume I should wind only 50 turns.

What do you think???


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## rustyknife (Sep 20, 2012)

Gld-

The wire selection, number of turns and resistance are all depen.dent on the output of your solar cells and how much room you have to wrap. You will want to measure the voltage and amperage of each of the cells, in full sunlight.

What your trying to accomplish is to make the strongest electromagnet possible.

This website does a good job towards the middle and end of explaining electromagnet calculations:

http://www.coolmagnetman.com/magdcem.htm

basically electromagnets strength are calculated by the amount of current flowing through the wire, and by the number of turns.

So say you have a solar cell that puts out .568 volts and .610 amps in full sun.

by rearranging ohms law, we know that if we divide our voltage by our resistance we can calculate the flow of current, or amps through the wire.

so we go to a chart that lists all the wire gauge sizes like so:

http://amasci.com/tesla/wire1.html

There we can see the diameters and resistances and then I just start playing with numbers.

Lets say it takes 12" of wire to make one turn of a coil on my motor. (you should measure yours and use that number)

if i use a 28 gauge wire and can make 200ft of wire fit at 200 turns then I can look at the resistance value chart and with a little math I know there should be around 12.8 ohms in that coil,

If I divide .568 by 12.8 ohms....I get a dismal .044 amps.  My solar cell puts out .610 amps, but I can't use them because I have made a poor selection of wire. .044x200 turns= 8.8 ampere turns or the strength of the magnet.  Remember thats in full sunlight. so if you want to make run inside, you must have the strongest magnet possible from your solar cells.

Well we need less resistance so lets go to a bigger wire.

Lets say I wrap a 23 gauge wire around it, but I can only get 120 turns or so physically on my motor. 120 feet of wire.  The resistance calculated out for this one is 2.44 ohms for the 120 feet.

.568/2.44= .232 amps x120 turns= 27.9 ampere turns, much stronger then before, but still not flowing up to where my cells are at.

    This is where choosing higher voltage cells or wiring them in series for higher voltage helps. The higher voltage will let you use smaller wire and more turns.   

Just keep playing with the number till you find one that suits your needs.  Hopefully I haven't confused you.   But you should have all the info in those two links that will lead you to success.


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## Ken I (Sep 21, 2012)

gld,
     Rustyknife is spot on - max current occurs at an impeadance match - but watch out for the actual conditions you would be running under - my testing of a limited range of photocells seems that full rating will only occur in direct vertical summer sun.

As regards the spreadsheet - something seems off - no sure what. If you dialled in all the correct values then I suspect your wire might be thinner than #36.

Either way I wouldn't lose too much sleep these things are pretty tollerant.

P.S. I have been trying to get full non-contact levitation using servo / feedback circuits but even here old Earnshaw is giving me a hard time.

Playing footsie with the laws of physics take patience.

Regards,
            Ken


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## gld (Oct 15, 2012)

Well I finially got mine to run. Ended up with 60 turns of wire, and my wire is # 36... Coils measured 20.4 and 19.6 ohms. My rotor has the wobbles so the end stops are just touching the ends. Balancing this is a royal pita. I cnc'd a clear plastic base and plan to show it at Zanesville.


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## rustyknife (Oct 15, 2012)

Balance is a royal PITA. Not only do you have to worry about the balance of the rotor, the power level of the solar cells contribute to a dynamic balance. I had one solar cell on my first one that was very weak compared to the rest and did not have the same level of power at low levels, caused quite a wobble


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## Ken I (Oct 16, 2012)

Yeah - Rustyknife - unequal solar cells do give it the wobbles - I also found that out - when I was given a bunch of cells I was horrified by the variability in output - fortunately I was given so many I was able to make up a matched set.

Also mechanical ballance is about the magnetic centre line which is never quite the same as its physical centre - this means that once you have ballanced the rotor, you can't move the rotor magnets (ie take it apart and reassemble) so if you do have to take it apart - mark the angular position of the magnet to get it back to the same place.

Ken


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