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Author Topic: Electronic Levitron...How the heck does this thing work?  (Read 76406 times)

Nink

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #45 on: December 02, 2014, 01:39:25 PM »
Since they are only tracking in the center I am not sure we would be accurate enough with a circle of infared receivers and an infared led in the middle and reflective tape on object.  We may need  an infared camera in the middle surrounded by infared LEDs in a circle with a small piece of reflective tape in the centre of the levitation unit. The levitation unit is a ring magnet with the centre covered and the small piece of reflective tape.   See Johnny lee infared tracking with the wii remote.   http://johnnylee.net/projects/wii/

Pirate88179

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #46 on: December 03, 2014, 04:10:09 AM »
Since they are only tracking in the center I am not sure we would be accurate enough with a circle of infared receivers and an infared led in the middle and reflective tape on object.  We may need  an infared camera in the middle surrounded by infared LEDs in a circle with a small piece of reflective tape in the centre of the levitation unit. The levitation unit is a ring magnet with the centre covered and the small piece of reflective tape.   See Johnny lee infared tracking with the wii remote.   http://johnnylee.net/projects/wii/

I think that the entire bottom of the floating magnet disk is mirrored.  At least, it looked to me like it was in the video on their website.  When they levitated the pillow, they just set the pillow on the magnetic disk...right?

I am still curious about the hidden version in the wooden desk top.  Like I said...only a small dia. area is visible on the desktop.  All of the sensors have to be in there...right?

Bill

PS.  Allelectronics has hall sensors for like $.75 ea.  For what that is worth.

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #47 on: December 03, 2014, 06:15:40 AM »
I just placed an order for ten Allegro AH3503 ratiometric Hall effect sensors from China. Cost for the ten: one dollar and ninety-eight cents. Shipping: two dollars. So I'll have them here in my mailbox in 10 or 14 days, for a cost of about 40 cents each.

Nink

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #48 on: December 03, 2014, 03:44:08 PM »
My local shop only has Hall switches for $4.99 each and they are just on off, they don't even sense magnet poll let alone provide voltage based on distance.

Here is how I think they are doing this with an Infrared LED in the middle of a circle of Phototransistors. The LED is slightly behind the Phototransitors so they can only see the reflected light when the reflected tape is directly above both the LED and the corresponding phototransistor  The Phototransitor then completes the circuit activating the appropriate electromagnet.   I am not sure if the electromagnets would need to go inside or outside of the magnetic ring, I guess that would depend on what is more effective, are we pushing or pulling, and what required the lowest amount of energy / heat to maintain a stable levitation.

Pirate88179

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #49 on: December 04, 2014, 05:16:45 AM »
Nink:

I think you are heading in the right direction there.  I just wish I had one to rip apart, ha ha.

Will an electro mag. work using AC?  (I can't remember if it will)  Because, if so, then won't the poles swap polarity at whatever freq. the AC is?

Bill

PS  I just looked it up and it will work.  So, could we not simply adjust the ac freq. to get the balance we need to hover a given weight?  Maybe use an air capacitor like in a radio?  Of course, we still need the surrounding perm mags to keep it centered but, I think it might be possible to simply "tune" the air cap. to adjust the freq to keep the ring magnet hovering.

Just a thought.

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #50 on: December 04, 2014, 05:53:43 AM »
With a lot of power you can levitate non-magnetic metals like copper or aluminum or brass with an AC electromagnet running at 50/60 Hz. The changing polarity of the field induces eddy currents in the metal piece and those eddys produce a magnetic field that opposes the field from the magnet (like polarities, switching very rapidly) so the metal plate rises up above the electromagnet pole pieces. John Hutchison did some of his fake videos like this.
It does take a bit of power though, and generates heat in both the electromagnet and the levitated metal. But no sensors or switching are needed, just the AC in the electromagnet. I used to demonstrate it with a "magnetic floor sweeper" we had at the lab, using a big variac for control and a chunk of aluminum plate for the levitated object. I don't have anything with the right pole pieces now, though.

allcanadian

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #51 on: December 04, 2014, 06:30:40 AM »
I built a hall effect based levitator a few years ago and they are fairly simple however there are a few tricks. The first issue you will encounter is hysteresis or feedback causing oscillations, next high current draw due to coil saturation if the magnet is too close or high current draw if the magnet is too far away from the coils. The most efficient layout I found was using a coil above in attraction and a weaker permanent magnet below in repulsion. The most efficient layout does not actually levitate the magnet with a coil but uses a permanent magnet to produce the levitating force and a coil to stabilize the levitated magnet. I also used a neat trick I discovered to stabilize a rotating motor/magnet being levitated, a 1/2" aluminum plate below the magnet will dampen oscillations however it will not hinder rotation. Remember the magnetic field is stationary in space and bound to the source as such rotation on axis does not produce any noticeable eddy currents or dampening effects however any other movement on any axis will. ;)

AC

allcanadian

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #52 on: December 04, 2014, 04:29:37 PM »
A few pics.
Maglev photo is a simple hall effect magnet levitation device and I was using a laser bounce system to map field inconsistencies.


The second photo is a magnetic bearing system I developed based on my magnet levitation experiments. Been sitting under the bench for a few years now but I was thinking of digging it out for the pulse motor build off. It works very well and is rock solid on all axis and by my estimate is a 99% passive system. Note on the far right outside column there is a silver aluminum disk in the column attached to the shaft, this is used to stabilize the shaft on all axis but does not dampen the axis of rotation as explained earlier.


The record for this bearing with only the 1" steel shaft spinning is continuous rotation for about 6 hours from 1000 RPM. By comparison a good set of ball bearings oiled with synthetic oil and the seals removed will spin approximately a minute or so. Interesting stuff and it becomes very apparent that a field is the ultimate bearing surface because it has literally no friction.


AC

Lakes

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #53 on: December 04, 2014, 05:42:39 PM »
I`d love to see any video you have of these devices.

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #54 on: December 04, 2014, 08:45:54 PM »
@AC: in the second photo, one end of the shaft is bearing against an end plate somehow, is that correct? That is, there is one point of actual contact between the levitated shaft and the support structure?

@Lakes: at the risk of boring you silly....

Optically-sensed, Arduino controlled:
http://www.youtube.com/watch?v=xkiGTWODERo

Electrostatically rotated, passive permanent magnet levitated:
http://www.youtube.com/watch?v=tVfw-TeJ9r4

This could also be accomplished with concentric ring magnets, as I presume AC is using in his system, and which Steorn used some years ago in their "Plinth" Orbo demonstrations at the Docklands. Still will need one point of contact with the frame, though, but will work vertically (as Steorn) or horizontally as AC's demo.
I have a set of such ring magnets but don't have the ability at the moment to construct a frame with sufficient accuracy and strength to support them.

Lakes

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #55 on: December 04, 2014, 09:53:57 PM »
Yup, I seen that (suspension) video and also the point contact (usually a lead pencil against a mirror) type using ring magnets.

If this is the type used from the above pictures, they were not clear enough for me to tell.

I`ll have to watch the electrostatic one though, not sure if I've seen that one.

Much more interested in your attempts at a "no-contact" type of levitation, but I am beginning to see how it works with the circle of permanent magnets as stabilizers.

Once that is working :) the next step would be to inductively light some LEDs as well. :D

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #56 on: December 05, 2014, 12:11:42 AM »
There is "no contact" in my coil-on-top maglev system and also no stabilizing magnet underneath. It's all done with optically-sensing the shadow of the bottom of the object and switching the coil on and off by the Arduino driving a power mosfet. The program in the Arduino corrects for ambient light by turning off the illuminating LED briefly every 100 pulses and sampling the ambient light falling on the photosensor, then correcting the pulse timing and strength so that the levitated object stays in the same position regardless of room lighting changes.

The system described by AC where the major lifting is done by PMs and then the coil just modulates that field, is a patented system that uses very little power, and also has the advantage of not dropping the object when the power goes off, instead the object jumps up and sticks to the PM lifting the weight. Sorry, I don't recall the inventor or patent number but it's available as a commercial display system as well. I think the electronic Levitron that is the subject here is also using that system, but inverted, acting in repulsion instead of attraction. Whether the field is sensed by Hall sensors, or the position sensed by optical means, is a question that is separate from how the levitation and stabilization is actually performed. Each sensing system has its advantages and disadvantages. I think a Hall effect sensing system will turn out to be more accurate and robust against outside perturbation, but also more difficult to implement in the actual build.

Still waiting for my Hall sensors from China, probably won't be here for another week at least.

Somebody (Lidmotor?) has demonstrated a top-coil levitation system that rotates the object and also lights up an LED inductively. I can't find the video at the moment, maybe someone else can. I did get an LED to glow a bit while being levitated in my system but not as well as Lidmotor (?) did in his.

Lakes

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #57 on: December 05, 2014, 12:35:32 AM »
The "coil on the bottom" system is more visually impressive, but of course more difficult to achieve.

I have seen a video where the "coil above system" is used to suspend a beer bottle and rotate it for an advertising display. :)

I will patently await the results of yours (and/or others) efforts for the "bottom coil" system. :)

allcanadian

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #58 on: December 05, 2014, 01:35:06 AM »
@TK
I thought about patenting my magnetic bearing as I have never seen one like it however it would be better served in the public forum... so here it is.


Take two magnets in attraction and slip a 1mm plastic shim between them, mine are N42 150 lb pull strength ring magnets. Now try to pull them apart, we cannot it's too hard so we must slide them apart pushing on one and pulling on the other. I was doing this when I thought Hmm...shear force?, why not have four magnets with a shaft in between the two inner magnets and a frame holding the two outer magnets attracted to the two inner magnets apart.


Frame--NS   NS--shaft--NS   NS--Frame


Now imagine the left hand side magnets pull 150 lb to the left and the right hand magnets pull 150 lb to the right thus the shaft in the middle is in perfect magnetic balance pulling neither left nor right when perfectly centered with equal gaps on both sides. The frame must be strong and rigid because the frame magnets are pulling with a force of 300 lb+ inward just as the shaft magnets are also pulling with a proportional force outward. The adjustment bolts are to set the 1mm gaps between the end magnets in attraction and to adjust for the fact the boards keep warping under the strain, lol.


The neat part is that the attractive magnetic forces are axial however the load acts radially downward, the load is carried by the magnetic shear force on the magnetic field between the magnet pairs on each end . I use a 5mm ball bearing on one end to stabilize the gaps and the axial load on the 5mm bearing is measured in grams while the radial load peaks at around 40 Kg on the bearing shown. Which raised a question in my mind, the pull force between the two magnet pairs can have literally any value (tons)while the magnetic shear force carries the load however if both attractive forces sum perfectly to zero then the axial load would still be in grams thus it is easy to see why the system is 99% passive.


In a perfect world the magnet gaps on each end of the load bearing shaft would be perfectly equal and the axial forces would sum perfectly to zero thus the axial load on the stabilizing bearing(s) would be near zero and the magnetic shear forces would carry 100% of the load.


I believe the idea really clicked while reading A.D. Moore's book on electrostatics at the time. That is a cube of aluminum the size of a sugar cube in which all the charges have been separated by a distance of 1 m will have an attractive force of 32 million million million pounds... and yet all of these forces somehow sum to zero in this little cube of aluminum. If that does not boggle the mind then I submit nothing will, lol.


It's yours use it.


AC




« Last Edit: December 05, 2014, 04:40:46 AM by allcanadian »

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #59 on: December 05, 2014, 02:03:46 AM »
I hate to burst your bubble, AC... but your system, if I am reading it right, is exactly the "Mendocino Motor" levitation system, also used by Steorn in the vertical plinth Orbos and also used by me in the video of the ES powered motor above.  I don't think you'll be able to patent it...

Steorn used powerful ring magnets, two on the shaft and two in the frame, and a hard ball bearing against a micrometer head for axial support and adjustment. This allows vertical shafting or other orientations. The Mendocino Motor design appears in certain magnetic desk toys (without the motor part) and also in many YT video demonstrations of motors, usually solar-powered with magnets and coils in addition to the opposing support magnets (rings on shaft, other shapes possible on frame), but always with the single point contact restricting axial motion. The usual design, as I've shown in the ES motor, only works horizontally because gravity provides the stabilizing force up and down. Concentric ring magnets as Steorn used mean that the magnets themselves handle all stabilization at right angles to the shaft.

In CLaNZeR's replication of the Steorn Orbo plinth, you can clearly see how the ring magnets are arranged, to produce forces in opposition just as you have described. The rotor/shaft assy is pushed _up_  gently against the axial adjustment screw and all the weight is supported by the magnets in repulsion. And the strength of the forces and the precision required is why I can't at present duplicate this system, my necessary tools are not available to me (they are in Ontario and I'm in Texas). Although I do have a set of the correct magnets, donated to me some time ago by a Steorn replicator from another forum.

BTW congrats on reading Moore's book. Not too many people know about his work. I guess you've seen my Dirod and some of the demos I've done with it.