I am building the levitation project featured on:
http://my.execpc.com/~rhoadley/magsus.htm
(The schematics start about halfway down the page)<p>I have built the first circuit block on the page, which works with the one SS495A hall sensor that I have. However, when I try to use a SS19T hall sensor there is no change in the output of the opamp at test point V1 when I move a magnet near the sensor, even though there is a change in the output directly from the SS19T. <p>The only significant difference between the two sensors that I can find is that the SS495A works rail to rail and the SS19T doesn’t. Otherwise, they seem to have about the same ratiometric operation as well as very similar internal circuit diagrams. <p>I would like to use the SS19T hall sensors because they are cheap and easy to find. Any insight into how to make them work would be appreciated. Also, if any of you know of a supplier that will sell small quantities of SS495A hall sensors, a link to them would also solve my problem. <p>Data sheets for the respective sensors are at:
http://content.honeywell.com/sensing/pr ... c20020.pdf
http://www.allelectronics.com/spec/SS-19T.pdf
Problem with Hall sensor
Re: Problem with Hall sensor
The SS19T data sheet describes the output as a sourced current. Only one transistor is shown in the output circuit, and the graphs have a notation indicating a 2000 ohm load.<p>The other data sheet indicates that the output bout sources and sinks current, and two transistors are shown in the output circuit.<p>The solution may be as simple as a 2000 ohm resistor to ground on the SS19T unit.
Re: Problem with Hall sensor
You had referencing available as per the units wiring into in your “Levitating Cannonball “circuit.
But what you really need supplementing that poor resolution datasheet is the “Hall Book”<p>http://www.honeywell-sensor.com.cn/prod ... llbook.pdf <p>And yes, you do need a loading resistor, or otherwise your output circuitry is at rails levels with no circuit continuity for outputs to be developed across.
Check in around page 10…Fig 2-6. Also the first of the book will cue you in on the fine points of Hall effect devices in general.<p>“Rots of Ruck” with your project.<p>73's de Edd
[email protected] ..….....(Interstellar~~~~Warp~~~Speed)
[email protected]….....(Firewalled-Spam*Cookies*Crumbs)
<p>[ July 24, 2005: Message edited by: Edd Whatley ]</p>
But what you really need supplementing that poor resolution datasheet is the “Hall Book”<p>http://www.honeywell-sensor.com.cn/prod ... llbook.pdf <p>And yes, you do need a loading resistor, or otherwise your output circuitry is at rails levels with no circuit continuity for outputs to be developed across.
Check in around page 10…Fig 2-6. Also the first of the book will cue you in on the fine points of Hall effect devices in general.<p>“Rots of Ruck” with your project.<p>73's de Edd
[email protected] ..….....(Interstellar~~~~Warp~~~Speed)
[email protected]….....(Firewalled-Spam*Cookies*Crumbs)
<p>[ July 24, 2005: Message edited by: Edd Whatley ]</p>Re: Problem with Hall sensor
Thanks, the loading resistor seems to have done the trick
Re: Problem with Hall sensor
John T:
I was too short on time at the last posting, but now I wonder if you might relay some info on as per your observations of the levitator that you have built. With the utilization of a different Hall, I would assume that you are trying to extend its performing capability or seeking to iron out some experienced shortcoming(s).
Specifically:
Are you getting about the same capture/suspension distance as the author did? That articles photo reference ruler is not distinct enough to read, but top textual reference mentioned 1 inch.
Is there any tendency of oscillation or bobbling of the suspension object?
Is the suspension stable enough to permit a very lightly gripping of the bottom of the bolt and imparting a spin upon it in its Y axis ?
Also, here are some specific thoughts on the bolt. The author certainly became cognizant within minute one of the necessity of maintaining the suspension magnet in a stable rotational axis at power up and its functioning mode. The bottom "gravitational ballast" provided by the bolt is analogous in a manner of problem solving as one might find in the fletching of an arrow stabilizing it in flight or the keel on a sailboat for its stabilizing effect. I wonder if you have experimented with the bolts selection? Two considerations specifically, the idea there being in the trade off the actual required length for magnet rotational stability versus the bolt length now being utilized. Just my thought, was that he had selected a bolt a bit greater in mass and length than would have been necessary. With that bolt hanging on, there will be a certain point where the magnets strength/effectiveness will be diminished if the parasitic bolts weight/length is more than just the amount required for stabilizing.
The second factor is the altered magnetic flux profile. With just a button magnet sitting alone, expect a uniform concentrated ellipsoidal magnetic flux pattern. If you then hang on that parasitic iron bolt, the pattern will then be altered to a lengthened psuedo-conical pattern , with somewhat of a tapering off of the flux effectiveness at the magnets topside, which would be the electromagnet / levitation interaction point.
Sooooo, at this point, I ask you, have you tried taking the magnet and sticking/centering it to the end of a wooden dowel of such weight/length as to fulfill the required stabilizing requirement but yet be transparent in not affecting the magnetic aspect of the situation, thus leaving the magnet to function at its optimum.
Personally, if that solution worked and extended the levitating distance, I would be equally impressed upon seeing a ? length of 1/2 in dia "steel rod" (dowel+flat alum paint) floating in air at a greater distance than the heavier magnet + iron bolt combo was levitating to. Or, if that variance worked, the effect could be further enhanced opon by using an even larger dia balsa wood dowel with the magnet inset into its end.
I guess the last specific query, was as to what semi you had used for the core driver, as he only mentioned the use of his Hi power/dollar semi or an even more costly op amp package alternative.
Performance wise, the remaining thought would be towards utilization of the strongest button magnet available, to be levitating along with its "companion".<p>The strongest button profiled magnets I have used lately are nickel neodymium-yum-yum..(heavy on the yum) types in a .251 height by .501 diameter sizing (they are .001 hard plated) I would strongly suggest trying one of them. Without inter-comparison of gauss specs with the one you are using, I could only say that if I place one unit on my open palms center and go to the other side of the hand with the other unit spaced/isolated away at a 2 in distance and rotate that unit on axis I can flip the top magnet over.
Ergo, if yours can roll over at that distance, you are in the equivalent strength of flux density, however, if your little doggie plays dead........
I have needed that specific profile and its .500 in dia sizing in the past for an instructional tool and been "scalped" by Scientific Supply Sourcing, et al, to the tune of $7.50 a copy.
Howsomever if you will check out:
http://www.bgmicro.com/pdf/catalog.pdf
There you will pleasantly find a set for < $2.00, seems like they were a new stock item inserted at the end of the catalog, but may have been moved, but their order ID # was ACS 1476 along with a touting of little giants with their "8 pound" pulling power.
Preferably, keep the pair apart or you are going to get finger tip calluses after multiple lateral separations of the pair.
I have some utilized for memo note holding in the van to its dash, with a magnet holding not a sheet..... but the complete thick pad being held down.<p>While still touching on the Physics/Magnetics aspect, you just might want to also try one more super simple magnetics experiment utilizing a magnet, whereupon a closed loop circuit encrouches upon or passes through its magnetic field or, in this case, just the converse. This effect is ever so more enhanced when incorporating the strong flux densities encountered in the supermagnet families.
This is the procedure:
Get the aforementioned magnet ....since, first we need one stroooooong magnet and that precise diameter specified is just right for a close clearance, yet free passage thru a 2-5 ft length of 1/2 in hard drawn copper pipe, such as we universally use for plumbing applicatons. The five feet figure threshold being where handling and observation becomes a bit unwieldy. (However, if you have a full 10 ft stick and don't want it cut, along with a full thirty seconds of effect/waiting time......use it)
Preliminary preparation is your inspecting the ends of the pipe selected for any end compression from a tubing cutter operation and reaming out as necessary for free magnet clearance. If its with factory cut smooth ends, you should be ready to go as is . A double final check, if on used tubing, is to sight out to a light source and see if no bends, kinks, internal trash or debris exist. (If you had to chamfer out the inside ends.) Loose internal debris can be cleared with a tissue packing-dowel rod push through. When observing the light flooded internal bore you can see what smooth internal manufacturing preparation was considered towards freeing flow friction or metal pore contaminants. On some brands, it almost looks as if it was polished internally with Brasso. BTW, I first zeroed in on this condition whilst helping a neighborhood kiddo in his fabrication of a dart blowpipe using my workshop facilities.
Final sizing:
Place the magnet, or a clustered pair for more effect, up to the hoz positioned pipes ends, it having a slight downward slope to the right for a final , pop in- fall out test for no constrictions being presented to the magnet(s). Then do the same test to the other end of the tubing.
The effect now:
Hold the tubing vertical and drop in the magnets and wait...and wait...and wait...and wait and then pick up your magnets that just hit the floor. Then you are going to have to do it again, since you probably didn't believe it the first time. Then you can view, from the top, watching the floating action with the daylight below encircling the adequate 98% clearance that the magnets are afforded, therefore only micro-minuscule friction co-effients are involved here! That can't be the explanation.
Congratulations you have just seen the inter reaction of a strong magnetic force field in a closed loop. In this particular case the 1 looooooooooooong shorted copper coil turn that the magnets flux field was concentrated into. You can forget that 32 feet per second free falling object in space axiom in this special situation, realistically, more like 4 inches per second. Should you want to get things back to normal, along with wasting that pipe, take your Dremel...every one has a Dremel tool , doesn't he?... along with a cutoff wheel and cut a full length longitudinal slot in it so as to open up that shorted 1 turn and then things will all return to normal. Also, if you are in the process of "messin' with someones mind" you would only want to use a single magnet since someone toying with two of them would reveal that metal "slug"/"pellet" being a magnet pair. Then when they think they have every thing figured out you can further confuse the situation by clinching a magnet in the encircled juncture of your little and ring fingers and hold the pipe with the thumb and first two fingers and use them to make a gradual pivoting action of the pipe such that the grasped magnets action can hold up the falling for a desired time period, before shifting back to let the falling unit free.
In the past, invariably the like effect was probably discovered by anyone that perchance had a small electric motor in his hand, with its magnet and armature coil structure, along with its required commutator for maintaining continuity to the armature while in its rotational state. Give the shaft a spin and expect a bit of freewheeling on that spin. Short across the motor terminals and then try spinning the shaft again, but whooaa....expect a definite counter reaction to your efforts to turn it this time. Or lastly, get the rotor spinning healthily and short the motor...screeeech. Soooooo everyone has probably done/seen the motor bit, but probably not the seen the simple magnetic field encroachment into a shorted turn...thus getting the effect down to its simplest basic viewable form without need of using any instrumentation route.
Comical Aside:
Should one not have/be using/ nor want to foot out for the price of 1/2 in cu tubing at currently~$1.50 a ft? I guess one could just carry a magnet/set and try it out on the dole at a Homeless Despot plumbing supplies dept.
Seems like some time back I needed a piece of that mentioned 1/2 tubing for a backyard faucet rework and upgrade to tandem faucets. Just after reaching the HD parking lot I caught myself in mid-stride and pivoted about to go back to grab one of those magnets from the van. Initially, thinking of the typically common influx of multiple salespersons confronting me and wanting to help me out. Nope, no assistance needed, at least ....not just yet...... I was holding out for help within the plumbing department. In that area I picked up my section of pipe and casually drifted over towards JACK ARMSTRONG, ALL AMERICAN and Master Plumber (and yet sometimes covertly, casual Homeless Despot Moonlighter Extraordinaire.)
Now, I had the option of kicking into the mode of one of either two alter personnas, either the Tesla coil frizzled hair, mouth- frothingly exuberant Physics instructor of PBS fame..."I'm Julius Sumptner Miller and Physics my game"..... or Delmer P. Dumbnutts, and naturally, the latter would definitely serve the situation better in this particular ploy.
Therefore, I approach him and query, "I have this here piece of pipe and have to be sure that some thing the identical size of this pellet/slug is going to pass through it and isn't going to hang up inside it. My eyesight isn't what it used to be, so could you double check and see that I've got the right size and that it isn't too small to use?
After turning the pipe horizontal and a couple trials of putting the "pellet" just barely inside one end with a fingertip and immediately tipping it out that same side, he assured me that no problems would be had, with apt clearance being inside. I then took the pipe as he had, and put it right under his nose, but with it being heavily at a slant and then I tried inserting the pellet, as he had done, but then I had to say "woops," as I had let it slip and fall down into the tube , but he is already lurching towards the floor to immediately pick up the errant pellet.....which he did...but with that happening only e...v...e...n...t...u...a...l...l..y. His immediate response being, "Let me have that !", expecting to find some internal constriction. After his repeating the procedure two more times ....HEY EARL!....COMMERE !......I got the gol-dangest thing here. Then we had Earl trying out and shaking the thing and observing ? "It can't be hanging up....its rattling loose inside." Finally the last of the plumbing crew was on hand and doing his on hands evaluation...... "Lookadis!",....."Lookadis!", with the ruckus having drawn in two more from the adjacent Paint section.That departments old "sage" proporting, loudly, multiple times...."I know what it is, I know what it is, its got to be something sticky in it!...while waiting to get his hands on the pipe. Looking around, it seems like a group of 11 or so had clustered around in fast order, including curious and equally baffled regular customers. In each case, the handler of the pipe, just doing a refeeding of that pellet down the pipe just as quickly as it would slowly drift down and eventually come out the end. "Its air pressure, not enough air pressure, it must be making a vacuum at the top"
At about that time, I just made my move up to catch the "pellet" while he was watching it float down and commented " It certainly looks like this will work out for me and be o k to use, so I'll just take this one, and then walked off to make my purchase.
Thus, in the end, resulting in other than yet a normally mundane day at the HD, but leaving a group in mass confusion<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled*Spam*Cookies*Crumbs)
<p>
I was too short on time at the last posting, but now I wonder if you might relay some info on as per your observations of the levitator that you have built. With the utilization of a different Hall, I would assume that you are trying to extend its performing capability or seeking to iron out some experienced shortcoming(s).
Specifically:
Are you getting about the same capture/suspension distance as the author did? That articles photo reference ruler is not distinct enough to read, but top textual reference mentioned 1 inch.
Is there any tendency of oscillation or bobbling of the suspension object?
Is the suspension stable enough to permit a very lightly gripping of the bottom of the bolt and imparting a spin upon it in its Y axis ?
Also, here are some specific thoughts on the bolt. The author certainly became cognizant within minute one of the necessity of maintaining the suspension magnet in a stable rotational axis at power up and its functioning mode. The bottom "gravitational ballast" provided by the bolt is analogous in a manner of problem solving as one might find in the fletching of an arrow stabilizing it in flight or the keel on a sailboat for its stabilizing effect. I wonder if you have experimented with the bolts selection? Two considerations specifically, the idea there being in the trade off the actual required length for magnet rotational stability versus the bolt length now being utilized. Just my thought, was that he had selected a bolt a bit greater in mass and length than would have been necessary. With that bolt hanging on, there will be a certain point where the magnets strength/effectiveness will be diminished if the parasitic bolts weight/length is more than just the amount required for stabilizing.
The second factor is the altered magnetic flux profile. With just a button magnet sitting alone, expect a uniform concentrated ellipsoidal magnetic flux pattern. If you then hang on that parasitic iron bolt, the pattern will then be altered to a lengthened psuedo-conical pattern , with somewhat of a tapering off of the flux effectiveness at the magnets topside, which would be the electromagnet / levitation interaction point.
Sooooo, at this point, I ask you, have you tried taking the magnet and sticking/centering it to the end of a wooden dowel of such weight/length as to fulfill the required stabilizing requirement but yet be transparent in not affecting the magnetic aspect of the situation, thus leaving the magnet to function at its optimum.
Personally, if that solution worked and extended the levitating distance, I would be equally impressed upon seeing a ? length of 1/2 in dia "steel rod" (dowel+flat alum paint) floating in air at a greater distance than the heavier magnet + iron bolt combo was levitating to. Or, if that variance worked, the effect could be further enhanced opon by using an even larger dia balsa wood dowel with the magnet inset into its end.
I guess the last specific query, was as to what semi you had used for the core driver, as he only mentioned the use of his Hi power/dollar semi or an even more costly op amp package alternative.
Performance wise, the remaining thought would be towards utilization of the strongest button magnet available, to be levitating along with its "companion".<p>The strongest button profiled magnets I have used lately are nickel neodymium-yum-yum..(heavy on the yum) types in a .251 height by .501 diameter sizing (they are .001 hard plated) I would strongly suggest trying one of them. Without inter-comparison of gauss specs with the one you are using, I could only say that if I place one unit on my open palms center and go to the other side of the hand with the other unit spaced/isolated away at a 2 in distance and rotate that unit on axis I can flip the top magnet over.
Ergo, if yours can roll over at that distance, you are in the equivalent strength of flux density, however, if your little doggie plays dead........
I have needed that specific profile and its .500 in dia sizing in the past for an instructional tool and been "scalped" by Scientific Supply Sourcing, et al, to the tune of $7.50 a copy.
Howsomever if you will check out:
http://www.bgmicro.com/pdf/catalog.pdf
There you will pleasantly find a set for < $2.00, seems like they were a new stock item inserted at the end of the catalog, but may have been moved, but their order ID # was ACS 1476 along with a touting of little giants with their "8 pound" pulling power.
Preferably, keep the pair apart or you are going to get finger tip calluses after multiple lateral separations of the pair.
I have some utilized for memo note holding in the van to its dash, with a magnet holding not a sheet..... but the complete thick pad being held down.<p>While still touching on the Physics/Magnetics aspect, you just might want to also try one more super simple magnetics experiment utilizing a magnet, whereupon a closed loop circuit encrouches upon or passes through its magnetic field or, in this case, just the converse. This effect is ever so more enhanced when incorporating the strong flux densities encountered in the supermagnet families.
This is the procedure:
Get the aforementioned magnet ....since, first we need one stroooooong magnet and that precise diameter specified is just right for a close clearance, yet free passage thru a 2-5 ft length of 1/2 in hard drawn copper pipe, such as we universally use for plumbing applicatons. The five feet figure threshold being where handling and observation becomes a bit unwieldy. (However, if you have a full 10 ft stick and don't want it cut, along with a full thirty seconds of effect/waiting time......use it)
Preliminary preparation is your inspecting the ends of the pipe selected for any end compression from a tubing cutter operation and reaming out as necessary for free magnet clearance. If its with factory cut smooth ends, you should be ready to go as is . A double final check, if on used tubing, is to sight out to a light source and see if no bends, kinks, internal trash or debris exist. (If you had to chamfer out the inside ends.) Loose internal debris can be cleared with a tissue packing-dowel rod push through. When observing the light flooded internal bore you can see what smooth internal manufacturing preparation was considered towards freeing flow friction or metal pore contaminants. On some brands, it almost looks as if it was polished internally with Brasso. BTW, I first zeroed in on this condition whilst helping a neighborhood kiddo in his fabrication of a dart blowpipe using my workshop facilities.
Final sizing:
Place the magnet, or a clustered pair for more effect, up to the hoz positioned pipes ends, it having a slight downward slope to the right for a final , pop in- fall out test for no constrictions being presented to the magnet(s). Then do the same test to the other end of the tubing.
The effect now:
Hold the tubing vertical and drop in the magnets and wait...and wait...and wait...and wait and then pick up your magnets that just hit the floor. Then you are going to have to do it again, since you probably didn't believe it the first time. Then you can view, from the top, watching the floating action with the daylight below encircling the adequate 98% clearance that the magnets are afforded, therefore only micro-minuscule friction co-effients are involved here! That can't be the explanation.
Congratulations you have just seen the inter reaction of a strong magnetic force field in a closed loop. In this particular case the 1 looooooooooooong shorted copper coil turn that the magnets flux field was concentrated into. You can forget that 32 feet per second free falling object in space axiom in this special situation, realistically, more like 4 inches per second. Should you want to get things back to normal, along with wasting that pipe, take your Dremel...every one has a Dremel tool , doesn't he?... along with a cutoff wheel and cut a full length longitudinal slot in it so as to open up that shorted 1 turn and then things will all return to normal. Also, if you are in the process of "messin' with someones mind" you would only want to use a single magnet since someone toying with two of them would reveal that metal "slug"/"pellet" being a magnet pair. Then when they think they have every thing figured out you can further confuse the situation by clinching a magnet in the encircled juncture of your little and ring fingers and hold the pipe with the thumb and first two fingers and use them to make a gradual pivoting action of the pipe such that the grasped magnets action can hold up the falling for a desired time period, before shifting back to let the falling unit free.
In the past, invariably the like effect was probably discovered by anyone that perchance had a small electric motor in his hand, with its magnet and armature coil structure, along with its required commutator for maintaining continuity to the armature while in its rotational state. Give the shaft a spin and expect a bit of freewheeling on that spin. Short across the motor terminals and then try spinning the shaft again, but whooaa....expect a definite counter reaction to your efforts to turn it this time. Or lastly, get the rotor spinning healthily and short the motor...screeeech. Soooooo everyone has probably done/seen the motor bit, but probably not the seen the simple magnetic field encroachment into a shorted turn...thus getting the effect down to its simplest basic viewable form without need of using any instrumentation route.
Comical Aside:
Should one not have/be using/ nor want to foot out for the price of 1/2 in cu tubing at currently~$1.50 a ft? I guess one could just carry a magnet/set and try it out on the dole at a Homeless Despot plumbing supplies dept.
Seems like some time back I needed a piece of that mentioned 1/2 tubing for a backyard faucet rework and upgrade to tandem faucets. Just after reaching the HD parking lot I caught myself in mid-stride and pivoted about to go back to grab one of those magnets from the van. Initially, thinking of the typically common influx of multiple salespersons confronting me and wanting to help me out. Nope, no assistance needed, at least ....not just yet...... I was holding out for help within the plumbing department. In that area I picked up my section of pipe and casually drifted over towards JACK ARMSTRONG, ALL AMERICAN and Master Plumber (and yet sometimes covertly, casual Homeless Despot Moonlighter Extraordinaire.)
Now, I had the option of kicking into the mode of one of either two alter personnas, either the Tesla coil frizzled hair, mouth- frothingly exuberant Physics instructor of PBS fame..."I'm Julius Sumptner Miller and Physics my game"..... or Delmer P. Dumbnutts, and naturally, the latter would definitely serve the situation better in this particular ploy.
Therefore, I approach him and query, "I have this here piece of pipe and have to be sure that some thing the identical size of this pellet/slug is going to pass through it and isn't going to hang up inside it. My eyesight isn't what it used to be, so could you double check and see that I've got the right size and that it isn't too small to use?
After turning the pipe horizontal and a couple trials of putting the "pellet" just barely inside one end with a fingertip and immediately tipping it out that same side, he assured me that no problems would be had, with apt clearance being inside. I then took the pipe as he had, and put it right under his nose, but with it being heavily at a slant and then I tried inserting the pellet, as he had done, but then I had to say "woops," as I had let it slip and fall down into the tube , but he is already lurching towards the floor to immediately pick up the errant pellet.....which he did...but with that happening only e...v...e...n...t...u...a...l...l..y. His immediate response being, "Let me have that !", expecting to find some internal constriction. After his repeating the procedure two more times ....HEY EARL!....COMMERE !......I got the gol-dangest thing here. Then we had Earl trying out and shaking the thing and observing ? "It can't be hanging up....its rattling loose inside." Finally the last of the plumbing crew was on hand and doing his on hands evaluation...... "Lookadis!",....."Lookadis!", with the ruckus having drawn in two more from the adjacent Paint section.That departments old "sage" proporting, loudly, multiple times...."I know what it is, I know what it is, its got to be something sticky in it!...while waiting to get his hands on the pipe. Looking around, it seems like a group of 11 or so had clustered around in fast order, including curious and equally baffled regular customers. In each case, the handler of the pipe, just doing a refeeding of that pellet down the pipe just as quickly as it would slowly drift down and eventually come out the end. "Its air pressure, not enough air pressure, it must be making a vacuum at the top"
At about that time, I just made my move up to catch the "pellet" while he was watching it float down and commented " It certainly looks like this will work out for me and be o k to use, so I'll just take this one, and then walked off to make my purchase.
Thus, in the end, resulting in other than yet a normally mundane day at the HD, but leaving a group in mass confusion<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled*Spam*Cookies*Crumbs)
<p>Re: Problem with Hall sensor
Edd the wicked magneto <p>TOK 
<p>TOK Gorgon the Caretaker - Character in a childrens TV-show from 1968.
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California Techie
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- Joined: Thu Mar 17, 2005 1:01 am
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Re: Problem with Hall sensor
That ceratainly looks like an interesting project. I also would be interested in the extra facts before proceeding. Has anyone made a PCBoard for it.
I guess that you have not checked back or are still busy on the project<p>Edd
I dwfinitely will have to get and try the magnetic flux braking experiment. It sounds like it falls as slow as a feather does.
I certainly enjoyed your hardware store escapade aat the end. I was rotflol. I repeat ROTFLOL !!!
Just my luck if I was to try the same thing I would encounter not a plumber , but an under employed Silicon Valley engineer or technician.
You may not remenber me but I initiated a post about my cranky Weller soldering station. Your supplied great info repaired it and is still working flawlessly. Next I will build the timer for it. Thank you ever so much again.<p>California Techie
Rex
I guess that you have not checked back or are still busy on the project<p>Edd
I dwfinitely will have to get and try the magnetic flux braking experiment. It sounds like it falls as slow as a feather does.
I certainly enjoyed your hardware store escapade aat the end. I was rotflol. I repeat ROTFLOL !!!
Just my luck if I was to try the same thing I would encounter not a plumber , but an under employed Silicon Valley engineer or technician.
You may not remenber me but I initiated a post about my cranky Weller soldering station. Your supplied great info repaired it and is still working flawlessly. Next I will build the timer for it. Thank you ever so much again.<p>California Techie
Rex
Re: Problem with Hall sensor
Sorry Edd, I haven’t been online for a while; <p>I’ll try to answer your questions the best I can, your knowledge of the physics of this kind of thing seems far beyond my own... <p>The only reason I am using the different hall sensor is that it is easier to purchase in small quantities. In comparison to the SS495A hall sensor that I have, which was supplied by Guy Marsden’s kit at http://www.arttec.net/Levitation/Kit.html, the SS19T is not quite as sensitive, and cannot detect a magnetic field from as long of a distance as the SS495A. However the SS19T does do the job, but I suspect that a better sensor might be a little more linear in its output and do a better job. <p>And yes, there is a strong tendency of oscillation along the y-axis. I had to replace the .01 capacitor along the integrator (the op-amp w/ output V4) with a variable trimmer cap rated in the picofarads just to get an object to levitate for a moment. This had the effect of increasing the sensitivity to the motion of the magnet, which subsequently increased the feedback response in the electromagnet. <p>I also had to tweak the frequency of the PWM as suggested by the article; however, interestingly I found that decreasing the frequency, rather then increasing the frequency of the PWM as done at http://tesladownunder.iinet.net.au/Magnetism.htm did the trick. I think this must have something to do with the induction of the electromagnet I am using.<p>With these changes in place I was able to suspend a large neodymium magnet (1” diameter by ¼” thickness) without a ballast a bit over an inch below the electromagnet (its hard to measure exactly because I have a piece of foam over the end of the electromagnet to protect the hall sensor and the magnet from breaking in the case that the magnet becomes unstable and slams into the electromagnet). With this configuration the suspended magnet remains stable for a bit over a minute before developing oscillations, which quickly build until the magnet is unstable. <p>Under my attempt at the articles set up, imparting a spin on the magnet is impossible. Although with ballast, one is able to nudge the magnet, I am unable to get it to remain stable while spinning. This is most likely because the magnet is slightly askew in its stable position; trying to spin it is analogues to trying to keep an oblong wheel rolling. I am unsure if this skew is from a crooked electromagnet, a misshaped end of the electromagnet or an uneven magnetic field of the suspended magnet or something else. <p>A foreseeable ill effect of spinning the suspended magnet is that this may induce eddy currents in the core of the electromagnet and the suspended magnet itself, which will oppose each other and cause problems at higher RPMs. However this probably will cause the electromagnet to slow down, rather then become unstable, and could be circumvented in part by using a ceramic magnet and laminated core for the electromagnet. An example of this phenomenon in action is placing copper or some other nonferrous metal below the suspended magnet, which effectively dampens oscillations. Your pipe trick is another well-illustrated example of this.<p>However, I do know that spinning the magnet is very possible, for in a previous project that used a light gate instead of a pair of hall sensors, I was able to get the suspended magnet to spin by blowing on its edge through a thin copper tube. This light gate project seemed to be very stable under the right conditions, but was finicky due to changes in ambient light. Another noteworthy aspect of this other setup was that the suspended object did not need to be magnetic, only ferrous.<p>As far as varying the type of ballast goes I have tried a number of different shapes and sizes. The most effective of this seems to be a steal nut that is about ¾” wide and ½” long. The shape of a nut may minimize the malicious flux change, but I really have no idea about that, (I tried to read a book on magnetic physics but my eyes glazed over once it started getting into differential calculus). More likely it seems to add sufficient mass while keeping the center of mass closer to the magnet, which seems to help. Adding a bolt also works but not quite as well. I additionally tried lengths of steal rod ranging in size from 6.5” to 1.5’, which worked for a time and was a good demonstration of the amount of weight this setup could handle. <p>Some of the more interesting things I added was a steal plate about 4” square by maybe a 1/16” thick. Surprisingly this also worked but only for a short time, for it accentuated the skew of the magnet. As far as nonferrous materials go, I tried putting the magnet inside a solder bobbin, but this proved too heavy for the setup, otherwise it was difficult to temporally fix the magnet to materials that do not naturally stick to it, so I never tried any other nonferrous materials.<p>As for your last question, I use a 2N3055 power transistor, which is pretty cheap and easy to find. When there is no suspended object my electromagnet draws about 1.8 amps, which causes the transistor to get scalding hot, but when a suspended magnet is in place, its magnetic pull towards the steal core of the electromagnet takes most of the brunt of the lifting and the power consumption falls in-between .1 and .3 amps, depending on the weight of the suspended object. While experimenting it is necessary to have no suspended object under the magnet for extended periods of time, so to avert damage to the transistor I have inverted it and partially submerged it in a dish of water and ice. Although a crude heatsink, this keeps the 2N3055 nice and cool as long as there is some ice. <p>Currently I am working on an idea of my own. That is to use two electromagnets to pull the magnet from both sides/poles of the magnet, so that a balance is achieved in midair. I think this might prove more stable then the other designs. I am basing the electronics of this largely on that of the before mentioned project, but still have quite a few bugs to work out.<p>[ August 05, 2005: Message edited by: JohnT ]<p>[ August 05, 2005: Message edited by: JohnT ]<p>[ August 07, 2005: Message edited by: JohnT ]</p>
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