Experiment issues (electromagnetism)

[Tyler184]

TL;DR Summary

I’m attempting to create an experiment to induce EMF from one coil inductor into another, yet being able to relate my observations with my math I did so I could control certain variables.

Hey guys, for some context, I’m a high schooler doing an experiment as a passion project, my issue today is an aspect of my project.

Anyhow, my ultimate goal is to be able to “remodulate” radio signals by converting them from AM to pulses in a magnetic field strength. While I bet there are many ways todo that, my specific approach requires the use of two inductors relationship via EMF. However, it is important to note, I’m not going straight in and remodulating radio signals just yet, I want to test the theory behind them first. Which is where this experiment is coming from.

The experiment consists of two inductors as previously mentioned, perpendicular to each other (one horizontal and one vertical), and I power the horizontal one to create a magnetic field and then I stop powering it after giving it some time to build magnetic energy and as the current drops so does magnetic field intensity therefore the flux drops and it results in a change in flux with respect to time therefore inducing emf into the second, vertical inductor.

Subsequently, I attached two probes of a MM at the end of the vertical inductor to measure the induced voltage. What I found quite odd was immediately after I powered off the horizontal inductor and began measuring the voltage in the vertical, I measured no induced voltage yet a compass I had on standby, was pointing towards it even as I revolved it around the vertical inductor showing it had its own magnetic field, and the only way it could’ve gotten that was by being induced with an EMF which then would store it as magnetic energy. Compasses are very sensitive unlike an MM so perhaps my MM didn’t catch the induced voltage although the MM was on mV mode therefore it’s unlikely it didn’t catch it cause the emf was probably in the mV range.

One thing I would like to mention as it’s quite important to know, is that I powered the horizontal magnetic field via a short (no resistance) by wiring up some AA’s batteries in series to obtain 7-8 V. I originally had resistors but I found they significantly hindered the strength of the magnetic field, on top of the fact I’m struggling as is to get proper readings with my MM.

Anyway, I attached a picture of my setup so you can see it. The core is a drill bit with a 2000 relative permeability I presume (steel core). The horizontal magnetic field is 175 windings at an estimate, 178mm in length, with a 5mm core diameter. And the AWG of the windings is 22. The vertical inductor is 252 windings, 56mm long, and 2.5 mm core diameter. With a AWG of 30. Moreover, the vertical inductor is held by a magnet in this picture however that was just to hold it for the picture so you can see how it was positioned during the experiment.

Additionally, with the magnet seen in the picture I did a side experiment by taking off the vertical inductor and varying the distance between the magnet and vertical inductor(basically if the magnet is in one hand and the inductor is In the other, just imagine bringing my hands further and closer together). By doing it I was able to develop a magnetic field powerful enough to pick up a small screw. I presume the magnet induced an EMF by varying the magnetic field strength/field flux.

Next, while the inductor still had its magnetic energy stored I decided to use my MM to again measure any possible induced voltage but I measured nothing which confused me. I’ve gone to my teachers who say my MM works just fine and isn’t the issue.

Moreover, my math also isn’t making any sense, as I’m predicting an EMF of 30-0.3V within 5 time constants of not powering the first magnetic field(yes volts, not mV) which is obviously wrong. I feel it would be best to fix the observations first then I’ll further discuss my math as to not make this thread too long.

 

[berkeman]

Welcome to PF.

The experiment consists of two inductors as previously mentioned, perpendicular to each other (one horizontal and one vertical)

You are trying to couple energy between orthogonally oriented coils?

 

[Baluncore]

Young Michael Faraday had similar problems, a couple of hundred years ago.

You have arranged the coils in a symmetrical way, such that the magnetic fields of the two coils do not couple. The magnetic compass is a more sensitive instrument, and is in a better position to detect the field.

If you lay the coils parallel, and next to each other, in an arrangement more like a transformer, you will detect a greater output.

 

[Tyler184]

Baluncore and berkeman, yes I am trying to couple coils perpendicular to each other. It’s part of a larger scheme later on to cause the needle to spin on a pivotal point by introducing a third external magnetic field which causes the remodulated AM radio signal (now stored through changes in magnetic field intensity of the vertical inductor) to vary with space (rotate at certain angle increments thereby converting the magnetic field modulation to mechanical modulation).

The mechanic modulation will then be converted to optic signal modulation. However, I haven’t thought too far with this due to the lackluster results I’ve been getting which I’ve been focusing on. I originally thought this experiment wasn’t going to work at all because most(basically all) coupled coils work in parallel as that’s the way the inductors magnetic fields align (shown through faradays work as you guys mentioned) but my method albeit significantly weaker, has received some results as said before thanks to the compass.

My logic was the emf would drive a current on the edge of the windings similar to how reactance works (when the stored magnetic energy drives a current in the windings opposite to that of the changing current polarity). Ultimately, I believe the main issue is the coil orientation however as of now, this current orientation seems to be the only way to obtain a rotating coil as if they were aligned, the magnetic field of the third inductor would disrupt the original inductor (as it would have to induce a emf that orients the second inductor but would hit the first in the process thereby hindering the radio signals strength as a magnetic field). Although perhaps theres a way that already exists of converting AM to mechanical modulation and then to optic signal modulation that I haven’t seen yet. Anyway, thanks for the feedback!

 

[Dale]

My logic was the emf would drive a current on the edge of the windings similar to how reactance works

And do you feel that your experimental data has supported that logic?

 

[berkeman]

It’s part of a larger scheme later on to cause the needle to spin on a pivotal point by introducing a third external magnetic field which causes the remodulated AM radio signal (now stored through changes in magnetic field intensity of the vertical inductor) to vary with space (rotate at certain angle increments thereby converting the magnetic field modulation to mechanical modulation).

You are not going to spin a mechanical indicator with AM radio (1MHz) or baseband audio (5kHz) frequencies. What are you trying to do in the end?

 

[Tyler184]

Dale; well, I’ve gotten some results from my experiment, just not much to make it anywhere near effective. However as previous said, I don’t know of any way to bypass the issue stated above of the external magnetic field inducing a emf on the first magnetic field if it were aligned with the second one.


Berkeman; my process consists of a radio signal introducing an emf which drives the current in multiple smaller vertical inductors(for this experiment I’m only using one). In the actual device I propose, the vertical inductors would be polarizers and be very light (lighter than the one I’m using for the experiment as this one’s just to measure the emf im employing). Additionally, on each end of the horizontal core would be a radio wave producer (like what garage doors employ for reference). The radio signal would go through go through the wall of polarizers and ultimately be encoded with an optical signal mimicking that of the radio.


Moreover, I understand very well they’re are critical issues with this type of remodulation, two big ones I considered is the lack of information storage (AM has complex data which a physical modulation may not be able to modulate as well). And the possible energy loss along the way, as what I propose is a complex journey from AM to optical modulation. However, I stipulate, by evaluating key points of the AM signal function by employing a certain amount of vertical inductors the same or proportional to that of the amount of key points I want to evaluate, I can recreate the signal to a decent extent through optical modulation. The best analogy of the math I can come up with is changing the limits of the h variable(not 0) in the derivative formula or better yet, the number of intervals in a Riemann sum except obviously in the opposite order (the derivative of the radio function as that relates to the change in flux).


If you would like me to go further and show the math I did (which I mentioned has flaws) to give you a better idea of what I propose I could do that too.

 

[Dale]

I’ve gotten some results from my experiment, just not much to make it anywhere near effective.

As a scientist, what do you conclude when an experiment contradicts a hypothesis?

 

[berkeman]

Berkeman; my process consists of a radio signal introducing an emf which drives the current in multiple smaller vertical inductors(for this experiment I’m only using one). In the actual device I propose, the vertical inductors would be polarizers and be very light (lighter than the one I’m using for the experiment as this one’s just to measure the emf im employing). Additionally, on each end of the horizontal core would be a radio wave producer (like what garage doors employ for reference). The radio signal would go through go through the wall of polarizers and ultimately be encoded with an optical signal mimicking that of the radio.

Sorry, this is word salad. What is your background so far in electronics, electromagnetics and signal processing? We want to help you, but that help will be different if you are a curious 10 year old kid versus a senior in high school...

 

[Tyler184]

Dale; well obviously I know it’s not an effective method as simple vector addition tells you this isn’t valid, however, I got some results (not much though). Furthermore, I don’t know of any other method that follows the conditions I mentioned above of aligning the magnetic fields so unfortunately this is all I’m left with.


Berkeman; my apologies let me try and reword it: My process involves sending a radio signal through an inductor to generate electromotive force (EMF) that drives current through multiple smaller vertical inductors in front of it (though I’m using only one for this experiment). The change of the current of the radio signal with respect to time is represented in the magnitude of the emf which is how the signal is transmitted. In the actual device I propose, the vertical inductors would function as polarizers and would be much lighter than the one used in the experiment, which is only used for measuring the EMF I'm applying. Additionally, at each end of the horizontal core, there would be a radio wave emitter (similar to those used in garage door systems to detect if anything is in the way). The point of this is the radio signal would pass through the many polarizers and ultimately be encoded with an optical signal that mimics the radio signal. Is this better or perhaps should I make a video or draw a diagram of what I mean in case my wording is still very confusing and ambiguous?


As for my background in electronics, I’m a junior in highschool, I self taught some vector calc (mostly curls, divergence, and gradients) and covered some of maxwells equations. Although I haven’t reviewed that stuff in a while and I’m not thorough with it, only a basic beginner so don’t hold me to that standard. Furthermore, I know differential and integral calc to the extent of calc 2 and some calc 3, but I only know basic multi variable equations that were primarily given at a calc 2 level. I’ve also built an AM radio receiver from scratch (although it was a crystal radio which is the simplest of all designs).

 

[renormalize]

In the actual device I propose, the vertical inductors would function as polarizers and would be much lighter than the one used in the experiment, which is only used for measuring the EMF I'm applying.

What exactly is being "polarized"? An electromagnetic wave? A dielectric medium? Something else?

Additionally, at each end of the horizontal core, there would be a radio wave emitter (similar to those used in garage door systems to detect if anything is in the way).

Do you really mean a "radio wave" emitter or is it actually a "light" emitter? In my experience, a garage-door-blockage detector uses an LED source to send a light-beam across the base of the door-opening, where the beam is received by a photodetector. There are no radio signals involved.

 

[Dale]

I don’t know of any other method that follows the conditions I mentioned above of aligning the magnetic fields so unfortunately this is all I’m left with.

And who set those conditions you are following? You or nature? When you have a failed result (and your result is a failed result with fairly clear reasons for the failure), then that is nature's way of telling you that you need to do something different. A successful scientist or an engineer cannot become so fixated on a specific design that you ignore clear signs that it isn't working.

You will simply not get significant coupling between inductors with perpendicular magnetic fields.

Frankly, the approach I would take would be to simply use an ordinary antenna to receive the radio signal, convert that to an ordinary electronic voltage signal, and then use that electronic signal to drive the optical device. The reason those things are ordinary is because they work.

 

[Tyler184]

Renormalize; an electromagnetic wave is being polarized. As for the garage door, I just thought of a quick example of what I propose, your right they probably use LED light beams. I haven’t thought enough or did enough research to consider whether I want to use laser technology or simply radio waves. More likely than not, I would use radio waves but again that can change.


Dale; Do you know of any modulation technique in particular employing what you say of converting RF directly to optical?

Lastly, something I forgot to say in my background although it may be irrelevant is that I have a background making a PMW circuit and briefly studying the inner workings of an electric motor which takes part in the motivators that made me come up with this idea.

 

[Dale]

Do you know of any modulation technique in particular employing what you say of converting RF directly to optical?

Sure. The general category is called amplitude intensity modulation.

https://en.m.wikipedia.org/wiki/Intensity_modulation

You are specifically looking for RF over fiber.

https://en.m.wikipedia.org/wiki/Radio_over_fiber