Electronic Levitron...How the heck does this thing work?

[Pirate88179]

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]

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]

--

[Pirate88179]

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]

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