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Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
How it exactly works? The two sensors are placed in a way to have the same flux and then subtracted to obtain a zero (equilibrium signal) but with a coil current different from zero. When a magnet or a ferrous material approaches the bottom sensor the flux increases and having the sensor on the noninverting opamp input causes the current to decrease setting the active equilibrium. So also we need an offset setting to set the "no load" magnet current, does it is right?
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
I suspect the lead compensation is dependent on the resting frequency of oscillation of the levitated mass. This will vary with the mass so you may find that a smaller mass like the battery you were using before might still be OK. Presumably bigger mass needs bigger cap.
Try levitating a non-magnetic object like a metal nut. I have levitated a wrench but couldn't keep it stable.
Registered Member #87
Joined: Thu Feb 09 2006, 01:36PM
Location: San Jose
Posts: 191
A quick thought, the system is a one sided transformer, so perhaps you could build a levitating peice with a coil inside, and power some l.e.d.'s in midair.
Registered Member #79
Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673
The levitator IR LED circuit was one of the first circuits that I ever attempted. It never worked well due to lack of a good object to levitate, and changing light made it cranky. Yours is much cooler!
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
TheMerovingian wrote ...
How it exactly works? The two sensors are placed in a way to have the same flux and then subtracted to obtain a zero (equilibrium signal) but with a coil current different from zero. When a magnet or a ferrous material approaches the bottom sensor the flux increases and having the sensor on the noninverting opamp input causes the current to decrease setting the active equilibrium. So also we need an offset setting to set the "no load" magnet current, does it is right?
Yes, the output of the two sensors are subtracted from eachother so we see just the difference caused by the magnet. This voltage is then amplified up to 20 times, them fed through the lead compensator and amplified 10 times more. This "offset" would idealy be 0v and would cause the 494 to put out around a 90% on time duty cycle. In real life, the opamps can't get down to 0v so the actual voltage the DTC pin of the 494 sees is about .6v. This works out just fine, because it limits the max duty cycle to about 80% on. This keeps things from overheating.
Firkragg wrote ...
Maybe you could make it levitate another levitator instead of that board, pick the power from the coil and levitate another small magnet...
Interesting idea, maybe ill try it sometime.
Tesladownunder wrote ...
I suspect the lead compensation is dependent on the resting frequency of oscillation of the levitated mass. This will vary with the mass so you may find that a smaller mass like the battery you were using before might still be OK. Presumably bigger mass needs bigger cap.
Try levitating a non-magnetic object like a metal nut. I have levitated a wrench but couldn't keep it stable.
Peter
Thanks for the suggestion. I have now installed a small socket so I can easily change out cap values. With a little playing with, I can probably make it more stable. It can levitate nonmagnetic objects but it draws alot of power(like 40w in the picture below). It actually seems pretty stable this way.
Anders M. wrote ...
CJK2, what sensors did you use on it?
The sensors are UGN3503U. I got them on ebay for $.75 each.
Self_Defenestrate wrote ...
A quick thought, the system is a one sided transformer, so perhaps you could build a levitating peice with a coil inside, and power some l.e.d.'s in midair.
I tryed that but as soon as the coil gets more than 1/2" away, the led goes out. I think it will take another set of coils runing at a higher frequency to get the power any good distance.
Part Scavenger wrote ...
The levitator IR LED circuit was one of the first circuits that I ever attempted. It never worked well due to lack of a good object to levitate, and changing light made it cranky. Yours is much cooler!
Thanks!
Well I hope I anwsered all the questions, feel free to ask if you have any more.
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
Yes, the output of the two sensors are subtracted from eachother so we see just the difference caused by the magnet. This voltage is then amplified up to 20 times, them fed through the lead compensator and amplified 10 times more. This "offset" would idealy be 0v and would cause the 494 to put out around a 90% on time duty cycle. In real life, the opamps can't get down to 0v so the actual voltage the DTC pin of the 494 sees is about .6v. This works out just fine, because it limits the max duty cycle to about 80% on. This keeps things from overheating.
I will limit the duty using the second tl494 comparator ( limiting the duty a 33% approx, correspondoing to 4A approx).
But would not the magnet suffer flux walking? Since each cicle che current does not fall to zero (dampner diode) che next cicle it will rise higher even with limited duty cicle. Wouldn't be necessary a current-mode control to avoid saturation? (this excludes the tl494 though..
Registered Member #76
Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458
mhh, thats a really cool project, im very impressed. i tried many different ways to levitate an object but with poor results. does anyone know if its possible to levitate a copper or aluminium disc stable via eddy currents(induction)?
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Magnetic levitation
