# A simple mechanical resonance demonstrator

"In physics, resonance is the tendency of a system to oscillate at maximum amplitude at a certain frequency. This frequency is known as the system's resonance frequency. When damping is small, the resonance frequency is approximately equal to the natural frequency of the system, which is the frequency of free vibrations." ( from Wikipedia, 8/8/2007)

With this Instructable I'll show you a simple rig that can be used to experiment with electromechanical resonance.
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## Step 1: Forewords

Of all the aspects of physics we can investigate with simple household items, magnetism is the most exciting to me. Although I'm sort of grown up I still love pushing magnets one against the other just to feel the magic repulsive force.
Repulsive force for some reason is more entertaining than the attractive one. In this field, I mean.

We know that when a current flows through a metallic wire a magnetic field is generated; that's what electric motor are based upon.
The wire can be wound in the shape of a bobbing to make the field stronger and a metallic core can increase the strength of the field. The equations linking number of turns, coil diameter and current can be found here (http://en.wikipedia.org/wiki/Electromagnet) but it is not strictly necessary to understand the underlying principles.
A direct current, the one from batteries, generates a constant magnetic field. The direction of the magnetic field with respect to current is established conventionally by the so-called right hand rule : with reference to the picture, grabbing the coil with our right hand with the thumb pointing the same direction of the current, the magnetic field will have the direction of the other four fingers.
The direction of current is, again, conventionally fixed going from the + pole of the battery through the wire to the - pole.
Alternating current (a.c.), the one that comes out a regular wall socket, will have the same effect except that the intensity of the current flowing through the coil wire cyclically rises to a maximum then decreases to a minimum in the opposite direction passing through a zero current level. As a consequence, a.c. powering a coil generates an alternating magnetic field that cyclically rises to a maximum value then decreases to a minimum passing through a zero field value.
It is important to note that the field does not rotate in any direction. Simply rises and falls in intensity then reverse its verse and rises again.
hgpt3 years ago
How many turns should the two bobbins have?
I remember i saw, once, a device who was using this property. The oscillating magnet was used (i don't remember exactly how) to produce current into a third coil. And the energy generated into the third coild was slightly greater than the energy supplied to the system ... giving, thus, a device with an efficiency slightly greater than 1. Though, chances are great that it was a pure hoax ...
6 years ago
No such thing as perpetual motion!
6 years ago
lol. Are your serious? When did the world stop turning????? And dont even get me started on the macroscopic....
3 years ago
In fact, the Earth's rotation is indeed slowing down. Google "earth rotation slowing". You'll get 111,000 results, like this:

My experience with perpetual motion is that it's impossible unless it somehow involves women. (Ducking sudden appearance of hurled frying pans and irons).

-Anonymouse
6 years ago
No, it is real. No it is not perpetual motion. The device is called the Vacuum Triode Amplifier, or VTA. Some also know it by its name previous to that, the Space Quantum Modulator, or SQM. The inventor, Floyd Sweet, used a special conditioning process to coax barium ferrite magnets into self-oscillation, at which point a small driver current was fed into a coil parallel to the oscillating magnetic field, and another output coil was placed perpendicular to them and yes, the deivice was capable of achieving overunity (COP/efficiency>1). However, the electricity it put out was unlike any other. It was a 'cold' electricity, and the device in question would run twenty degrees celsius BELOW ambient temperature. Hope this helps. Cheers.
Mhhh, a perpetual motion machine ? D'oh !
7 years ago
It's frustrating. I'm still unable to find it ... I remember it was related to diode or transistors (a kind of "mechanical" transistor maybe ?) ... Tsss ... that's internet ... when you're not looking for something special, you find it. And when you're looking for something special, you can't find it .....
7 years ago
Technically, that could be. Though, it was not what the device i was talking about was used for ... Damn, I don't remember the name of this device neither the name of the inventor ...
CameronSS7 years ago
Could you turn a DC adapter into an AC one by removing the rectifier? I haven't had occasion to pop open a wall wart--I don't know how the rectifiers are attached.
3 years ago
You can as long as it's not a SWITCHING power supply. An AC supply requires a transformer. These are quite heavy for the amount of current they're rated at. All of my 1 amp transformer based supplies weigh in around a good half pound, and get pretty warm in use. My 1 amp switchers are maybe an ounce or so, and if these get warm, something's usually wrong.

Switching supplies are usually labelled as such.

-Mike
5Volt (author)  CameronSS7 years ago
Yes you can, provided that the adapter is based on an 'heavy' iron transformer. Lighter ones (those of most modern and most expensive cell phone ) use special ('switchers') techniques to deliver DC from line. They are not good to the purpose. Inside they look like a regular electronic circuit with small (less than 1" x 1") components.

The AC in 'heavy' iron transformer based adapters can be taken right at the wires coming out the transformer (should look very similar to this one http://en.wikipedia.org/wiki/Image:Transformer.filament.agr.jpg ) before they go to the rectifier. The rectifier could have the shape of a black tiny cylinder or box or could be made with one, two or four diodes.

<disclaimer>
Be careful and stay away from the primary high voltage.
Always make connections with the adapter off line.
Always seek help from expert friends.
</disclaimer>

If you need more directions just write.

Ciao e divertiti. (have fun)
technick295 years ago
Really cool. I'm taking a physics course dealing with magnetism / circuits and this is a great real-life scenario and application of concepts you see in textbooks. I will definitely try this: experiments always make science more fun. Good job.
5Volt (author)  technick295 years ago
Thank you, just consider that the more current goes through the windings the stronger the field ( as you of course already know ) and stronger the effect. The magnet might be also thrown away if the field and the magnet are very strong, be extremely careful, use safety goggles. Ciao Alex
3 years ago
Using a strong magnet allows you to "bias" the circuit. Otherwise, both positive and negative half cycles pull nonmagnetized objects, effectively doubling the frequency.

The same can be done with a DC current flow equal to the maximum peak to peak current of the amp. Ohms law can be used to determine this.

-Mike
drjim65 years ago
Interesting project! However, my Windows XP won't play the avi movie file :-(
3 years ago
It will if you have the proper codec. I tired of looking, and now use Media Player Classic Home Cinema.

and get all the codec's you'll ever need:

http://sourceforge.net/projects/ffdshow/

-Mike
Chimney Toes4 years ago
Hello!
Thanks for this instructable. I am interested in the tuning you mentioned. I am working on a project using electromagnetic force to vibrate objects for musical purposes. what is the tuner? might i be able to use it to excite different resonant frequencies in a given form ..say a metal bin? i am new to this art form ..having spent some years playing with ceramic material i am now in the middle of metal things and vibrations are forever calling me! any thoughts on how i could play the different partials of an objects with eltromagnets? smile. thanks
5Volt (author)  Chimney Toes4 years ago
I think you refer to the last step and the razor tuning screw.
In case of a large bin you may need to to tune the oscillator frequency as the bin is home to a large number of natural frequencies. In case you need a sinusoidal oscillator, a large strong coil with an iron core, a power audio amplifier suitable to drive the coil and a large magnet to be placed somewhere around the bin or at its bottom. Connect the coil to the amplifier (do not connect any speaker - expect that you might destroy your amplifier, so you'd better not use your home Harman Kardon HiHiFi amplifier).
Turn on the amplifier at a low level first and place the coil near the magnet on the bin then start playing with the frequency of the oscillator to excite the partials of the bin. When you hear something interesting, pull up the volume and enjoy.
Again, be prepared to damage your amplifier, wear safety goggles as the magnet might be ejected.
Ciao
A

3 years ago
To protect expensive (or even cheap) power amplifiers, for solid state, use power resistors in series to insure the minimum load the amplifier is specified for, i.e. 2 ohms. Shorting a solid state amplifier will fry it.

If it's a tube amp, the opposite is true. You must NEVER operate a tube power amp with no load. It will generate high voltages that will arc the power tubes and output transformer. Tube power amps will withstand output short circuits that would quickly toast a solid state power amp.

-Mike
4 years ago
Thanks a mil 5Volt . Ambitious..i shall get an amp worthy of the ride. Actually i'm thinkng about using a well tuned bell as the frequencies are many and known. I even hope to vibrate the bell into a hum audible without an amp.. i hope its a ride worth jumping in.. hmmmm..or should i hitch an amp? my investigation continues.. smile.
5Volt (author)  Chimney Toes4 years ago
Oh, about the hum : in case, the amp must of course have a good passband towards the DC...
I was thinking 'bout creating a feedback with a microphone on the bell (screened from the speaker) : together with a phase-shifting network one should be able to force the bell into a partial.
This thing is calling me...Argh ! No ! No, have to finish the MIDI thing first !

Cheers !
Alex

dantheflipman7 years ago
One mistake i saw in step one, (its a common misconception) electricity actually flows from the negative (-) end to the positive (+) end of a power source at all times
4 years ago
Yes, current flows neg to pos.  I have many first sources right behind me.  The common connection, + to -, we owe to the late great Ben Franklin.  He got it wrong (sort of like Original Sin) and we have to suffer with this  until Judgement Day!
3 years ago
In electronics engineering, we still consider current flow going from positive to negative. It's called "Conventional current flow". O course we know that actual electrons flow from - to +, but this doesn't hold up mathematically. Conventional current flow is necessary to make the math work. It is mathematically impossible to have positive as a deficit and negative as a surplus.

So blame it on math.

-Mike
5 years ago
That is what they teach in electronic engineering courses, but in electrical engineering, they claim the opposite. I am an electronic engineer, and we were taught that electrical engineers are taught the opposite. Personally, I believe you are correct, my text book was correct, our lab experiments were correct, and electrical engineers can think what they want. Meters will show neg. to positive in DC circuits. I still have the same meter I got from a parts store for automotive electrical to show what direction the current was flowing and how strong it was.
4 years ago
my electronics engineering course teacher started out by telling us that while electrons actually flow to + from -- (DUH, electrons have a negative charge, they wouldn't flow to the same charge), we all use what's called "conventional current flow", which is + to --.

in short, you're right. lol

-Cheers
5Volt (author)  dantheflipman7 years ago
Electrons and electric current flow in opposite direction the latter one being defined in the early days of physics. Since then the convention is that electric current flows from pos to neg ( http://en.wikipedia.org/wiki/Conventional_current#Conventional_current )

7 years ago
i was talking about the flow of electrons :]
5Volt (author)  dantheflipman7 years ago
:) Ciao
Waren-Neutron4 years ago
it is so great invention you are a genius
Waren-Neutron4 years ago
now is i know that
8bit6 years ago
Great idea. And great handle (name) by the way.
Logicisking7 years ago
It does not matter how you apply Kirchoff's voltage law for the voltage drops through resistors. You can apply it positive to negative or negative to positive of the battery terminal and it will still turn out right. So this debate of direction is mute.
5Volt (author)  Logicisking7 years ago
There's no debate.
sanity7 years ago
I had an electronic shaver once, and it kept burning my face. I later discovered that the end piece (the shield) was missing. That will teach me for buying second hand goods :(
5Volt (author)  sanity7 years ago
Brrrr, shaving without the steel shield... how daring !... Ciao !
vaiden7 years ago
Telslas' inventions make good use of induction as in his tesla coils and his Magnifying Transmitter. Anyone who does not know that he is the father of radio as well as polyphase transmission of AC power, not to mention the inventor of the AC(induction) motor, and discovered x-ray before the man credited for it; thereby making him the pioneer of our entire civilization, should google him. He operated a radio controlled boat in 1890.
gamer7 years ago
so darn intense. nice job, i think i am gonna go make one, i have like 30 stepper motors. by the way, is Ciao e buon divertimento in italian? thank you- gamer
5Volt (author)  gamer7 years ago
Ciao e buon divertimento stand for well, 'hello' and 'have a good time' Thank you