Amplitude and Frequency

[Electro132]

Hi,

Ok, so its been about 1 - 2 years i've been researching and have found what i was looking for. I need some help in designing and building it so here goes:

I plan on building a project which allows me to change the amplitude and frequency of a waveform. This is then fed through an output which is capable of handling high currents at low/high frequencies. How the design and components are laid out i have still to determine.

For now, I plan on using Quartz Crystal Resonator Oscillators. I think if these were applied with a current it should be used as the waveform's frequency but i'm not sure if i need 2 for the maximum and minimum threshold frequency. Also these will be used for the output frequency to determine how far it will travel.

Hopefully this project can get started soon.

 

[Electro132]

Links to read up on are:

http://www.radio-electronics.com/info/data/crystals/quartz-crystals-resonator.php

http://www.fpga4fun.com/oscillators.html

 

[BobK]

We know what resonators and oscillators are. What we don't know is what you think you are going to do with them.

Bob

 

[(*steve*)]

And to expand on your requirements...

To change the amplitude you need either an amplifier or an attenuator (depending if you want it greater or smaller). Or possibly a transformer.

To change the frequency... Ummm. There are frequency doublers and stuff like that which can be constructed, but to do the variable frequency "auto-tune" type adjustments actually requires some fairly significant computing power, not what you can ever hope to build with discrete devices or logic.

As per BobK, not sure where resonators or oscillators even fit in with either of these things.

 

[Electro132]

And to expand on your requirements...

To change the amplitude you need either an amplifier or an attenuator (depending if you want it greater or smaller). Or possibly a transformer.

To change the frequency... Ummm. There are frequency doublers and stuff like that which can be constructed, but to do the variable frequency "auto-tune" type adjustments actually requires some fairly significant computing power, not what you can ever hope to build with discrete devices or logic.

As per BobK, not sure where resonators or oscillators even fit in with either of these things.

Ok well i'll clear some of these things up. First of all, the purpose for this is to make a wine glass resonate and break into pieces for my experiment.

The resonator, as it says, only has one frequency it resonates on. So this means that when the wave comes out it won't be amplified at all to make the wine glass break at the right frequency. I know that wine glass can break from Amplification, but this will only amplify the frequency it is resonating on and not the pitch of the frequency.

So overall, I need to create a circuit which will allow me to change the pitch and amplification of the resonating frequency which will come from a quartz crystal. This will then be fed through the output of which i would like to use on the wine glass from at least 5 meters.

 

[Electro132]

Just an add on, i think it would be best to be able to select specific frequencies from a signal than have a specific signal.

Not sure, but i'd like to try out both designs if possible

 

[Harald Kapp]

I won't comment on this one...

 

[duke37]

If the wine glass is to break, you will need a high quality thin wall glass not a thick chunky one. It will only break when driven at its resonant frequency and it will take time for the vibration amplitude to build up.

The Q of the glass will be high so the driving frequency must be accurately tuned to the particular glass. Fixed frequency generators, using quartz crystals, are of no use here.

I would suggest a variable audio oscillator, either square wave (simple) or sine wave (better), should be used to drive a standard audio power amplifier and speaker. You will need to adjust the frequency very carefully to hit resonance. Close coupling between speaker and glass will be necessary so 5m is out of the question.

A sound level capable of damaging hearing may well be necessary. What personal liability insurance do you have?

 

[Electro132]

If the wine glass is to break, you will need a high quality thin wall glass not a thick chunky one. It will only break when driven at its resonant frequency and it will take time for the vibration amplitude to build up.

The Q of the glass will be high so the driving frequency must be accurately tuned to the particular glass. Fixed frequency generators, using quartz crystals, are of no use here.

I would suggest a variable audio oscillator, either square wave (simple) or sine wave (better), should be used to drive a standard audio power amplifier and speaker. You will need to adjust the frequency very carefully to hit resonance. Close coupling between speaker and glass will be necessary so 5m is out of the question.

A sound level capable of damaging hearing may well be necessary. What personal liability insurance do you have?

Well no insurance. But i know that the pitch of the resonating frequency can be changed, so the frequency can move fast or slow meaning that the wine glass can vibrate depending on the amplification and the pitch. Together i think it is possible to make the glass break with a fixed frequency because according to physics, the more an object moves back and forth the more it will rebound moving the object out of its original position

That's why i wanted to do this experiment because i think with both the right pitch and amplification the fixed frequency can break the wine glass. Please correct me if i am wrong.

Also if quartz is out of the question then would it be possible to use a parabolic dish to control the vibration wave and shoot it out in a particular direction?

 

[BobK]

If you are going to do this, wear ear and eye protection.

Bob

 

[duke37]

If you run a damp finger round the rim of the glass, you can get the glass to resonate so you can determine the frequency needed. The sound level can be quite high. To make the glass break, you will need a level mucch higher than this and very accurately matched in frequency. It may take several seconds for the vibrations to build up.

If you wish to use a directional source such as a parabola you should measure the frequency, calculate the wavelength and make a parabola a few wavelengths across.

To show the effects of mechanical resonance, make a pendulum and see if you can make it swing at a frequency which is not the natural frequency. To energise it, use an thin elastic band pulling the pendulum close to the pivot.

 

[davenn]

If you wish to use a directional source such as a parabola you should measure the frequency, calculate the wavelength and make a parabola a few wavelengths across.

But of course thats not going to happen for a sound, ( an audio signal) as the wavelength is HUGE!!

Dave

 

[duke37]

The wavelength can be large. Bottom C organ pipes will be 32ft long for half wave but a piccolo is only a few inches long.
The speed of sound is about 340m/s so the wavelength at 6800Hz will be 340/6800 = 1/20 or 50mm (2 inches). Quite within the possible range of a parabola.

Perhaps Electro132 could make a glass ring, record the sound and use Audacity to determine the frequency.

 

[davenn]

my mistake ... not sure why I was thinking it was much longer ??


D

 

[BobK]

my mistake ... not sure why I was thinking it was much longer ??


D

Because you were thinking of radio waves? At audio frequencies they are huge.

Bob

 

[duke37]

Here is a picture of an acoustic parabolic mirror. Not very portable !

 

[Electro132]

If you are going to do this, wear ear and eye protection.

Bob

I'm deciding on building a resonator oscillator first then, since i can change the frequency, i'll add that to the square wave. but i'm curious to see whether the wine glass will break with triangle or sawtooth waves as well?

I think if the waveform was to reach above 120 db (at volume measurement) then it should break it. and with a parabola then it should be able to direct it towards the wine glass.

 

[duke37]

What square wave will you be adding?

The glass will resonate at a certain frequency, you should make an experiment to find out what this is. Once you know the frequency, you can make an oscillator and chose a transducer to generate the sound.

You can generate a square wave, sine wave or triangle wave, they will have the same effect. The square and triangle wave will have a fundamental component plus harmonics. Only the fundamental will do the work. Fourier analysis will tell you how much of each frequency is in the waveform. The square wave would be the easiest to generate since a linear amplifier is unnecessay.

 

[davenn]

Wouldn't it be better to produce a sine osc at the correct freq ( well with a little adjustment)
Yes as you say a square wave will work but you are wasting lots of power in all the harmonics instead of concentrating the power on a selected freq ?

Dave

 

[CDRIVE]

Just an add on, i think it would be best to be able to select specific frequencies from a signal than have a specific signal.

Huuuuuuuuuuuuuuh? What does that mean?
Chris

BTW, you obviously missed that Myth Busters episode.