Hi! I'd like to move particles on a surface from one side to another by vibrating the surface without the gravity pulling it
sideways, and I have some good idea how to do it. Let's do a flash forward to the future and see the result.
F*ck. It's not working!
So did it work? Don't tell me I'd like to make it.
I have a good feeling about it.
The whole concept is based on Chladni's vibrating plate creating figures due to standing waves.
I'd like to make my own plate using a speaker as an actuator.
As you know, a speaker is a magnet and a coil that when you excite the coil with an AC voltage, it vibrates at the
same frequency.
[Speaker buzzes at 60 Hz] AAH
[Capacitor explodes] F*CK!
I need another speaker. See, every speaker has its own rating. So for an 8
ohm speaker like this running on 120 volt AC it needs to be rated at 1800 watts.
Anyway...
Let me explain Chladni's figures of it, although Physics Girl Diana explains it very well in her video you can watch.
But let me see if I can do a quick summary.
[calm voice] Basically, when you generate a wave in an infinite medium, it will travel forward forevah!
Unless there is a change in the transmission medium, like a material change or a blockage, and the wave
reflects from that change and returns.
Now, the energy of the waves pass through each other like a Holy
Spirit through a wall.
[back to normal voice] But! The effect of the two energies acting on a single particle in the
transmission medium is the sum of the two energies.
For example,
if you have two waves like this in a given time,
the sum of the two waves at this point is positive. Here is zero, and here is negative.
So when the original wave and its reflection add up, instead of a wave moving one way, you get a wave that looks
stationary, which is called a standing wave with nodes and antinodes. And that's why this video is sponsored by ExpressVPN!
Oh my god, I can't even integrate...
Well, the thing is that I'm seeing more and more comments from my Chinese and Iranian viewers, which means that VPN is clearly working!
So I'd like to promote it. If you also like a secure and non-restricted Internet experience, get three months of
free service on a one-year package at expressvpn.com/electroboom
after which it's less than seven dollars a month, with a 30-day money-back guarantee! [Sniffs armpit]
I personally use their service, especially while travelling to secure my Wi-Fi connection among other things. Back to standing waves.
We like to vibrate the string or the surface at resonance frequency, because at resonance with a tiny bit of input power,
the waves add up and create massive waves.
For a string, you could resonate at different frequencies with the string length at half a wavelength, a full wavelength,
One and a half wavelengths and so on. These resonance frequencies depend on the speed at which the wave travels through the medium
Which depend on the material, tension, weight, etc..
Same thing happens in the 2D or 3D mediums. The waves
Reflect from the edges and surfaces and create all sort of standing waves.
I've already shown you there standing waves the microwaves generate on a cardboard box in the oven compartment.
Assume this is the cross-section of a vibrating plate.
If you pour sand on the plate where there are antinodes with the maximum vibration the sand jumps up and can't stay.
But it settles on the nodes where the vibration is minimal and that creates the Chladni's figures.
Let's make one. I'll make mine using these foam boards
I bought from a dollar store and these twist-on wire connectors and a speaker, a houses speaker, which I call Nancy.
[laughing] You know, Nancy Pelosi, the House's speaker.
I cut my foam board into a 1 foot by 1 foot square. It's a little bit warped, but it should work.
[Microphone change] I hot-glued a connector to the middle of the board.
[Back to normal mic] Then I hot-glued a connector that acts as an standoff
Right on top of the speaker, as level as possible.
There you go. Something like this.
Now, we have to drive the speaker and you can use an audio amplifier
if you have one, or in my case, I have designed my own circuit a while back
which I can drive from any audio jack or a function generator.
Now we can attach the magnet of this speaker to a steel pan
so it doesn't move around. Now, I drive the speaker using a sine wave from my function generator, trying to find out the resonance
frequency of the plate. Right now it's at hundred hertz. And if I change the frequency,
[Function generator beeping]
You see, at around
117 hertz, it becomes louder. So that's one resonance frequency, and harmonics of that would make the plate resonate.
Now we pour a bunch of salt on the plate and
start the speaker to see what happens.
[Function generator beeps, silence, then salt rattles]
Hehehe, look at that!
Beautiful! It worked perfectly! See, the salt stays at the nodes of the standing wave where the plate doesn't vibrate
This was at 117 hertz. Let's try other frequencies.
[Piano music and salt rattling]
169. There is a cloud of very tiny particles on the surface, see?
360 hertz.
It's interesting. It seems like these spots can hold very light particles like a cloud.
519.
A foam board doesn't work as good as those nice and straight metal plates they use but hey, it works well!
Now that we made this,
I want to see if I can move the nodes of the standing wave over the surface and move the particles with it
If I can make it happen, I can even move the particles uphill. Now,
here's my thought. What if I have actuators on both sides of the plate, and create my own wave and
fake reflection to create my own standing waves. Hmm?
Then I can vibrate one say at 100 Hertz and the other one at 101 Hertz
The frequency difference results in the source waveforms to slowly shift relative to each other. See, here
I have two frequencies with one hertz difference
and this is the sum of the two. The frequency difference is SO small,
the plate would resonate with both
frequencies and, looking at their sum, the nodes of the wave would shift one way. To visualize it a bit better
you can look at my video of the water levitating with strobe light. The water is
vibrating at some frequency and the light is blinking at a slightly different frequency
and it seems the water is moving slowly one way or the other. This time
I cut a narrower piece of board and I hot glue two standoffs at the middle edges of the board and
hot glue it on two speakers nice and level. Oh boy. I hope it works. Fun fact:
Did you know that plates can have two or more different main harmonic resonance frequencies? For example, in this plate the wave
reflects a shorter distance this way and a longer distance that way, that creates two different resonances.
Did you know there are bells made to have two different frequencies? We can try this here. Here I have a glass that makes one tone.
[Glass making a tone]
We can see the frequency spectrum on my phone.
[Glass making a tone]
Only one peak at 1.1 kilohertz. Now, I added magnets to the glass as weights
so it resonates slower this way and faster that way. Now if I flick the glass, you see two peaks.
[Glass making more tones]
Now, I have to update my audio amplifier so it can output two channels.
[ow]
Okay, so first we have to figure out at what frequency this plate oscillates,
around 330 hertz. Now, I turn this on at 330 and that one at 331.
[Pulsing, a bit distorted]
Yep, you can hear it pulsing. What I mean by pulsing is that when you're adding two different frequencies
they drift over each other like this,
so when they are in phase, they add up,
or when there are 180 degrees off, they cancel each other. And if I zoom out, you see that the resulting
waveform is pulsing. The speed at which this pulsing happens is equal to the difference between the two frequencies.
Now we pour salt on it.
Well, it's moving around a little bit but not as I hoped. I'll just play music on it so you don't go crazy.
So it's pulsing at 1 hertz right now, because the difference between the two frequencies is 1 hertz. Now,
I'm gonna bring the frequencies closer so the pulsing is a slower. But the noise is killing me!
Well, I was hoping for a better result,
but I guess we learn through disappointment.
It does move around a little bit,
but I was hoping for the salt to move from one side of the plate to the other side
Let me put back the square plate on the speakers and see if I get any better shapes.
Okay, on the bigger plate it waves a little bit more.
Just remembered that I have a piece of glass. Glass can resonate much better than a foam board. Let me replace this with that.
I'm a bit afraid of resonating glass though.
But the glass is much heavier for my tiny speakers to vibrate. Seems like it's making these crack lines.
AAAOW
Well, at least the glass didn't break but there was no waving action.
I think I understand why combining two frequencies still didn't work. Yes,
I have two different frequencies at each end,
but that doesn't eliminate the fact that each wave also reflects from the edges of the board.
So on the same line, the first source has standing waves like this and the second one like this, slightly shifted,
so the salt only oscillates between these two nodes rather than a sweeping node across the board.
Maybe my idea would work if there were no reflections from the edges of the board, but I don't think that's possible.
Let me just glue one speaker at the center. I think it might look much better.
The glass is probably too heavy for my speaker to vibrate.
Yeah, the glass is too heavy for my tiny speakers, let me stick it on my subwoofer, should be able to vibrate it harder.
It's interesting. I can clearly see the resonance in glass, see?
It's vibrating here and there's a node around here. Then it's vibrating here. Let me increase the amplitude
so the vibrations are more visible.
[Glass breaking] OH SH*T
Well, F*CK
That definitely changed the resonance frequency of the plate. Well, I guess that's why they do it with metal plates.
They don't break. Back to my two speaker setup. If I just run one of the speakers and utilize the reflection of
one of the waves,
at low frequency, I only create one node.
As you can see here. See, with one speaker power and changing the frequency on that speaker
I can push my particles forward.
I can even bring it back, see?
So it's possible to some extent. There are videos of holding particles in midair using standing waves, and they can move them around, too.
But in their setup, they have hundreds of ultrasound speakers and by tuning them individually,
they can slightly move things around. Maybe there is some good application for it
But one thing that for sure works is ExpressVPN!
It frees your internet access from local restrictions because you would connect through the country of your choice,
which also makes your location private. It also encrypts your data.
So if you have to connect to some shady Wi-Fi network,
the guy next door connected to the same network won't be able to hack into your data.
So, to take advantage of all these features, visit my link below to learn more and sign up. Thanks for using my link.