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Author Topic: Electronic Levitron...How the heck does this thing work?  (Read 76405 times)

Pirate88179

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #15 on: November 29, 2014, 07:20:03 AM »
Bill,  the way to do it is to use an H-bridge, or equivalently an op-amp circuit, that will switch output polarity in response to a sensor input. Two example "sketches" are below. Just substitute the coil for the motor M in the circuits. These are bare-bones sketches of course, the real circuit will have some more complexity depending on your sensors, power supplies, etc.
You'd need relatively highpower op-amps that can source and sink sufficient current on the outputs to the coil. Like maybe OPA549 from TI.

TK:

Thank you for the schematics.  This is now over my head but, I will research more on this.  I am surprised that the levitron folks are not using a chip of some kind...but...maybe they are...we don't know what is inside there for sure.  I am also not seeing how they are using sensors as, the base only shows leds pointing up.....maybe ir like you said before but, would the sensors not have to shoot across the bottom of the hovering base?  (In a horizontal fashion)  If they are just pointing up, how can they sense if the disk is rising or falling?  Do you think they might be angled a bit so the light bounces off of the bottom of the disk?  (and hits the receptor at a certain angle) If the disk gets too high the light misses the receptor...same if it gets too low?

I don't know why I am so fascinated by this...probably because I can't understand it...ha ha.

Maybe someone will chime in here who has one and has taken it apart.  Or, maybe i can try to contact some of those folks that said in their reviews that it quit working after a few days and see if they want to make a few bucks on the now useless unit?

Bill

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #16 on: November 29, 2014, 08:43:35 AM »
TK:

Thank you for the schematics.  This is now over my head but, I will research more on this.  I am surprised that the levitron folks are not using a chip of some kind...but...maybe they are...we don't know what is inside there for sure.  I am also not seeing how they are using sensors as, the base only shows leds pointing up.....maybe ir like you said before but, would the sensors not have to shoot across the bottom of the hovering base?  (In a horizontal fashion)  If they are just pointing up, how can they sense if the disk is rising or falling?  Do you think they might be angled a bit so the light bounces off of the bottom of the disk?  (and hits the receptor at a certain angle) If the disk gets too high the light misses the receptor...same if it gets too low?

I don't know why I am so fascinated by this...probably because I can't understand it...ha ha.

Maybe someone will chime in here who has one and has taken it apart.  Or, maybe i can try to contact some of those folks that said in their reviews that it quit working after a few days and see if they want to make a few bucks on the now useless unit?

Bill

Well, the video shows that the disk has to be pretty carefully positioned over the base for the thing to "catch" initially, using the corner visible LEDs as indicators. Those LEDs could be part of the sensor system, or it could use Hall effect sensors somehow. The patent shows some LEDs and maybe photodiodes in the sensor loop, but just as sketches, not real complete circuits. I can think of a couple of ways that converging and reflected LED beams could be used.

Contacting someone with a failed unit might be worth doing, if they haven't been able to get any satisfaction from the distributor as far as returns go. It would be interesting to see what they are using. There are several "chips" that could handle most of the functions: quad op-amps or even motor controller chips. The high power op amp I listed earlier is kind of like a many-pin TO247 package, like a big mosfet.

I went ahead and put together that last circuit I posted, just as a lark, to see how it worked. I made a little demo video, it should be ready to view in an hour or so once it finishes rendering and uploading. It's easy and works great, with a potentiometer input. I haven't tried using it with a Hall sensor but it occurs to me that maybe the sensor from a computer fan might be made to work, like the one I used for the magnet polarity indicator. I dunno, I'll have to think about that one. For sure it will work with a 2-photocell (photoresistor type) voltage divider.  I'll post the link to the video when it's done.

ETA: Here's the video:
http://www.youtube.com/watch?v=-hNEpCwRX_k

John.K1

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #17 on: November 29, 2014, 12:00:32 PM »
--

Pirate88179

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #18 on: November 29, 2014, 07:08:00 PM »
Well, the video shows that the disk has to be pretty carefully positioned over the base for the thing to "catch" initially, using the corner visible LEDs as indicators. Those LEDs could be part of the sensor system, or it could use Hall effect sensors somehow. The patent shows some LEDs and maybe photodiodes in the sensor loop, but just as sketches, not real complete circuits. I can think of a couple of ways that converging and reflected LED beams could be used.

Contacting someone with a failed unit might be worth doing, if they haven't been able to get any satisfaction from the distributor as far as returns go. It would be interesting to see what they are using. There are several "chips" that could handle most of the functions: quad op-amps or even motor controller chips. The high power op amp I listed earlier is kind of like a many-pin TO247 package, like a big mosfet.

I went ahead and put together that last circuit I posted, just as a lark, to see how it worked. I made a little demo video, it should be ready to view in an hour or so once it finishes rendering and uploading. It's easy and works great, with a potentiometer input. I haven't tried using it with a Hall sensor but it occurs to me that maybe the sensor from a computer fan might be made to work, like the one I used for the magnet polarity indicator. I dunno, I'll have to think about that one. For sure it will work with a 2-photocell (photoresistor type) voltage divider.  I'll post the link to the video when it's done.

ETA: Here's the video:
http://www.youtube.com/watch?v=-hNEpCwRX_k

TK:

That is a really cool circuit.  Once I watched the video, it became clear to me on how this thing works.  I think that the bottom surface of the floating disk has a mirrored surface and the leds/senders/receptors could be angled to shoot up at a slight angle such that the beams bounce back down to the other side of the base to each other.


                                                                 _________  (levitating disk)
                                                                .               .
                                                               .                  .
                                                              .                     .
                                                             .                        .
                                                            .                           .
                                                       [--0---------------------0--]     (base)
                                                         
                                                         Led                       Sensor

Something like the crude drawing above maybe?

Thank you for making that circuit and the video.

Bill

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #19 on: November 29, 2014, 09:15:10 PM »
You're welcome, it's fun to play with.
Yes, that reflection idea is one that might work indeed.
I just made another video using CdS photoresistors instead of the potentiometer, it's uploading now. I'll put a link when it's ready. Still haven't tried it with a coil but that's coming soon.


ETA: Video:
http://www.youtube.com/watch?v=SUsA-YuAtBU

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #20 on: November 29, 2014, 10:45:57 PM »

Pirate88179

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #21 on: November 29, 2014, 11:29:55 PM »
Magnet hopper:

http://www.youtube.com/watch?v=onga0XPFs44

 :P

I commented on your video and don't want to repeat myself but.....this is excellent!  Clearly showing the pole reversal on the coil controlled by your photo sensors.  What ga. wire is on your coil?  Also, do you have an iron core in the coil?

This is so cool to watch you reverse engineer this device.  I hope a lot of folks are watching this.

Bill

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #22 on: November 30, 2014, 12:34:16 AM »
#33, no core, perhaps 1500 turns, it's one of the test coils I made for the PerPenduPetulum. Its resistance is too high, really, which is why it doesn't burn out the transistors by drawing too much current. They don't even get warm. For a real levitator you'd want to use heavier wire to get more current, and power transistors or mosfets.  Also I think the CdS sensors might not be optimum. Probably better to use phototransistors or photodiodes, or even a specialized Hall effect sensor system. I'm still thinking about all of that.

Nink

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #23 on: November 30, 2014, 05:25:12 AM »
Magnet hopper:

http://www.youtube.com/watch?v=onga0XPFs44

 :P

Very cool TinselKoala Put a fan blade  (or your flat piece of wood) on the motor so when the fan covers the sensor it will reverse and cover the other one and reverse again. Why no idea :-) but would be fun to watch.

I guess you could also try throwing a bar magenet in your coil and create a bidirectional solenoid. Put sensor top and bottom so when the magnet pokes out one side polarity reverses and hopefully catches it in time and forces magnet out the other side of the coil and repeats.  Again no idea but would be fun to watch. 


TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #24 on: November 30, 2014, 09:53:55 AM »
Very cool TinselKoala Put a fan blade  (or your flat piece of wood) on the motor so when the fan covers the sensor it will reverse and cover the other one and reverse again. Why no idea :-) but would be fun to watch.

I guess you could also try throwing a bar magenet in your coil and create a bidirectional solenoid. Put sensor top and bottom so when the magnet pokes out one side polarity reverses and hopefully catches it in time and forces magnet out the other side of the coil and repeats.  Again no idea but would be fun to watch.

Ah... great minds think alike. Actually one of my YT subscribers m3sca1 suggested this first, although I was already thinking of it. So yes, I did it, sort of, and it works. I call it the MescalMotor in his honor... sorry, I already named it before I saw your post! Next version may be the NinkMotor.  I made a video and when it is  done rendering and uploading I'll post the link here.


Again, thanks for the suggestions!

ETA: Video is up:
http://www.youtube.com/watch?v=ZqtKoFifby0

 8)

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #25 on: November 30, 2014, 09:55:10 AM »
I liked the first vid with the motor,, the chopstick you were using was making it move,, I had to watch it twice just to make sure I was not just seeing things :)
Yes, the photoresistors and op-amp make it very sensitive, it responded even to the very thin shadow of the chopstick!

Nink

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #26 on: November 30, 2014, 01:37:14 PM »
Wow works better than I thought it would. Nice work. I may try building one with a couple of hall switches next week (wife has me doing Christmas lights this weekend )

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #27 on: December 01, 2014, 02:54:46 AM »
Horizontal mounting:
http://www.youtube.com/watch?v=cgikT9HEiyM

Draws about 50-60 mA at +/- 13.5 V wrt 0 reference, and the little transistors I used are hot but not scorching.
(BC556B and BC337-25)

Nink

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #28 on: December 01, 2014, 04:21:27 AM »
Horizontal mounting:
http://www.youtube.com/watch?v=cgikT9HEiyM

Draws about 50-60 mA at +/- 13.5 V wrt 0 reference, and the little transistors I used are hot but not scorching.
(BC556B and BC337-25)

Nice did you stick it on a sessaw and see if it would balance ?

TinselKoala

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Re: Electronic Levitron...How the heck does this thing work?
« Reply #29 on: December 01, 2014, 08:17:46 PM »
Nice did you stick it on a sessaw and see if it would balance ?
No but I'm sure it could be made to do so.

One thing that may not be obvious is that it would not work with a simple bar magnet in there. The magnets stuck onto the rod ends are oriented like this:

N:S===[[[[[coil]]]]]]===S:N

So that the  coil always attracts from one side and repels from the other side. When the coil reverses polarity, the attraction/repulsion sides swap ends.