Great video thanks for your time and effort it is much appreciated. You are a great teacher! I know you did this years ago but your videos are helping an old fella get his head around electronics today.
So much positive feedback for negative feedback! The kids of my colleagues at work get a kick out of this each year during Bring Your Kids To Work Day. Thank you Shahriar!
man so cool...your description is so simple to understand. anyone with basic knowledge in electronic can make. you make it that so simple... There is complicated circuits for this but this one is simply the best..
OH.MY.ALLAH. I've been looking for a way to build an electromagnetic suspension device like this for so many days now! I was scratching my head and piecing together scraps of research but was getting increasingly frustrated - to the point of thinking of giving up.. You have seriously saved my life with this tutorial. Very informative and has everything I need. I'm an instant subscriber! You are helping to inspire and teach countless students young and old all over the world. Thank you.
As I have commented many other times, you are a good guy! it is so awesome and inspirational that you are giving back, it makes me want to be a better person... Back in the 90's I did a very similar magnetic levitation project as part of a controls class final project except we needed to do a full blown analog controller, as I recall it was much more complicated than your approach. Thanks again
The full schematic of the project is available on my website. All the part numbers are available and there is even a link on where to buy the electromagnet. The rest is up to you! :)
I love the two Hall-effect sensor idea, that's genius. It appears as if you have damaged the two large electrolytic capacitors during your fine-tuning. the tops of them are obviously bulging after too much heat was generated internally.
Well, there's another one that you hit straight out of the ballpark. Super! Absolutely stupendous! If you're ever in Houston I'd be happy to buy you a beer! Thanks for all of your hard work.
The system has feedback, it does not operate in open loop. In fact, it won't work in open loop at all. There is feedback around the error amplifier which goes all way the way through the electro-magnet, Hall-effect sensor before it is fed back to the error amplifier.
Thanks. Watching your video always gives a high as if I am physically doing it. You clear the possible doubts on the way and is a very effective teacher.
this helped explain hall effects pretty well. I'm currently trying to make a diy 500g-1kg (it be great if more) electro magnetic levitator with conventional metal infused PLA filaments with my 3d printer. its a very slow tedious process but im finally making some leeway in my current prototype demo thanks to this video. I need to find a real ferrite outter circle though for the 3d printed electromagnets (used electromagnetic filament for the base of the 4 electro magnets and copper wire wrapped around)Thank you!+thank you to all the commenters putting a lot of other equations here.
A wonderful project and a top-notch explanation of the theory behind it!. Your videos are always instructive and entertaining. I really appreciate the effort.
Your videos are so creative and well explained. Who would ever have thought to use levitation as a lead in to understanding PLL's. Genius.......... Thanks
Another great video. Instead of KA7500 you can also use TL494, AFAIK they are identical and both can be found in old computer psu, best way to recycle old parts.
I have to say that this video was absolutely awesome to say the least! To be honest, for some of your other videos, I have stopped watching after 10 minutes or so because they have been way too fast progressing, too complicated with advanced terminology and generally difficult to follow. This video was the complete opposite. Easy to follow and understand, which made it VERY interesting. Thank you.
Excellent experiment. Simply put : Food for the brain :). BTW I know students from the local university that follow your channel with 10x more dedication than all the courses they are having.
Thank you very much for your effort for making this very educational video. Your teaching style is innovative, not many people make cool projects and explain them.
You are right. But what I meant is that the IC would work much better, as PWM controller, with some feedback at the error amplifiers. In open loop, with the near infinite gain, the amp works as a comparator and the system runs as bang bang control. The ringing inside the Ton time of the output square wave is the hysteresis loop working at the middle of bandwidth of the feedback loop.
I absolutely love your videos and the way you can explain difficult subjects. im glad you're reaching a milestone in the amount of subscribers, that only means we get to enjoy more quality content. thank your Mr Shahriar.
Another great video. Much appreciated. You are in inspiration to so many - the 5k subscribers you mention at the end of the video is now 30k! Including me. :)
This is the best video on this project. I am building this right now so it's very useful. I have one question: Is it necessary to establish a PWM using an oscillator, or I can directly use the output of the op-amp to turn the electromagnet on/off? I don't have the KA7500C IC, was wondering if I can use something else instead if I understand what's needed..
Awesome video! One small correction - I think that the magnetic field very near to a magnetic dipole actually changes as 1/r^3, not 1/r^2. This is the due to the difference between a dipole and a monopole (like a point charge).
I was searching for someone to point this out as soon as I started watching. Worth noting that the cubic relation also makes control that much harder. Or put another way, the sensitivity of the control system is higher. That much harder to get the dampening right.
Of course, the force between two dipoles is even more complicated to calculate. There are multiple terms, though 1/r^2 terms are involved in most situations (unless the magnets are much smaller in scale compared to the separation, I think).
Excellent video. And excellent project. Congrats!! Would it be possible to omit the hall sensors and take the feedback from the tiny current that the magnet induces to the coil? Forgive my question I only understand a fraction of what You exposed... My understanding of electronics and circuits unfortunately is minimal... I have an idea of a project that I believe would be very interesting in aeronautics. ( I am only a naive and humble hobbyist ). Thank You and best regards. Victor Micha.
This system is barely stable. The open-loop transfer function is something like 1/(s^2 - 1), which has a pole in the right-hand plane. The negative feedback creates a closed-loop transfer function of 1/(s^2 - 1 + g), where g is your loop gain. This give a pair of complex poles on the y axis, which wouldn't normally be stable, except that you have a tiny amount of air resistance. If you differentiate the hall-effect signal and add that in your feedback loop, making the feedback path (g1 + g2*s) I believe if would improve stability by pushing the complex poles solidly into the left-hand plane.
Katia Gyetvai He's right though.. look at the oscillations... Also, his system is unstable because he uses a very simple regulator (most likely only P). If you use a properly tuned controller, such as PID, these problems will dissapear. I also doubt he did a simulation before that to check the transfer function.
I totally agree. But the problem then is to tune the system with the proper amount of differential gain to get stable response. In my experience designing one levitator that way, yes it gains marginally better stability at the expense of hours of tuning.
I did a project like this also two years ago for a class on instrumentation design. We used an arduino to read in the voltage from the hall effect. I wish I would have thought of a second sensor on top. the way we tried to cancel out the coil to cancel oscillations was to sample the sensor when the PWM was low (while trying to make sure the inductor was fully discharged) I have a couple videos of it in my channel if you want to check it out
How about those of us who understand feedback and control theory and want to understand theory, design, and implementation of phase locked loops. Would you make a video?
Great video but little correction, on 29:40 you describe that pwm is turned off that it do burst of pwm what is not case, what you describe as pwm burst are some oscillations in circuit (they are to high frequency to be from pwm), instead pause and what you describe as pwm bust are one pwm period.
That's a pretty damned cool party trick :D I wonder if this might benefit from using a latching current mode PWM controller such as UC3843 rather than the very basic TL494 equivalent you have. You would have intrinsic cycle by cycle current limiting, so shouldn't need the big power resistors; have the latch to stop the multiple switching transitions per cycle you see on the scope; and the current loop which makes the electromagnet into a voltage controlled current source, taking its behaviour as an inductor out of the equation makes the whole thing intrinsically more stable and more tolerant to variations in loop compensation at the error amplifier. At least I know about this in switching power supplies, but I can only guess as to how well this translates to this circuit. I might try it but I don't have the magnets, electromagnet or hall effect sensors, so I probably will procrastinate and eventually forget about it.
I am uncertain how well it work with something like that. It all depends on how much the steel ball influences the magnetic field going through the Hall effect sensor at the bottom, and I am not sure if it will have a strong effect on it.
Great video, really takes the snore out of my controls class and gives more intuition as to what and why i study controls. But if i do build this gadget i'd probably try to make it levitate using a knight rider effect on it. But again thanks for the inspiration and intuition, looking forward to more videos from you.
Possibly a soft iron core would allow the magnet to approach quite closely, since the electromagnet field would be very low when it was largely unenergised. The steel has too much remnance.
you are a pro mannn !! I admire your willing to explain and especially your professional and easy understanding explanations!!! !(: I incurage you to continue with your stuff I would like to ask what is the difference between this method of controlling to a pid s ?controlling ! does your controlling is the "p"part from the pid technique
This should also work with steel ball, right? Ball can rise a bit magnetic field at bottom so there must be little difference on exit of 741. This is amazing video. I wish that my uni. prof. were as good as 1/10 of you.
I'm a subscriber now, but in the video you stated that the instructions are on the web - can you point me to them? I would like to recreate this - you don't happen to have the ARDUINO or ESP32/8266 versions do you? I love to play with experiments and this would be something I really want. Thank you again for your videos!!!
G8 video sir, nice explanation. I want to make repulsive electromagnetic levitation and I am from IT branch so I don't know about microcontroller and sensors. Plz make a detailed video on this topic also. Hope u will rply me.
32:33 In this setup where you can invert the current in the electromagnet, how would you deal with the voltage spike? Since the diode would not be in the correct orientation.
William, thanks for your observations. Would you please recommend some easy reading material that would give me a good understanding of poles,zeroes and how you saw that the stability would improve by pushing the complex poles solidly in the left hand plane? - Thx
Not really useless. As you can see in the single shots, the PWM is neither at 0 or 100% but somewhere in the middle (with ugly ringing). So it's doing PWM. But I don't know if there's any advantage in using the IC. Replace it with another opamp comparing the FBV and the set voltage and feed the output directly to the FET gate. Should be able to levitate the magnet and would be worth a try (oscillations could be a bigger problem with this setup though).
Great video! I will propose this for Bring Your Kids To Work Day. I'm wondering, though, if having reverse current when the ferromagnetic attraction force exceeds m*g, would cause stability issues as pushing does not offer an equilibrium point in the 2 other directions as pulling does.
I really like those probes you have to convert the oscilloscope probes to something you can connect to a bread board ... any idea what they are called and where I might get some?
first of all, i must tell you that i'm really happy to see such a professional yet simple approach to building this circuit. now, i have one question: what time base did you set on your oscilloscope? i'm planning to build something like this but more simpler (with just one hall sensor and one comparator) and i need to know approximately how much does my comparator needs to be fast :)
Great video! Thank you for making it for us. You mention that the Hall Effect Sensors that you used were too sensitive. Do you have a recommendation for a better HES for this project? Please and thank you.
Thanks for a great effort. But did you consider the effect of placing the Hall effect sensor at the centre of the lower core section, in terms of disrupting the magnetic flux.
If you levitate the magnet ABOVE the coil and flip the levitating magnet, then all you would need (theoretically) is a single-polarity circuit (i.e. what you already have).
Has that PWM controller got a derivative term that is not shown? This system should be unstable in the purely proportional form as it has to compensate for errors of distance as well as inertia.
I know just one question. How to make it reply. I want to keep the induced current magnet on the table and magnets which are to be levitated on top of that. What are the changes I have to make in the circuits. Keep do tell me. Thank you. I really like you are videos. I am an electronics student and I love the way you explain the circuit and component And that helped me a lot in my academic as well.
