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Passive amplification of a specific audio frequency range(microphone)

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Shploop
#37
May17-13, 01:07 AM
P: 24
Well I can't give you numbers because I don't know them, I don't have a measuring device.
I said that I want ambient sources like street noise, heres a list of sources and their SPL in dB:
http://www.engineeringtoolbox.com/so...ure-d_711.html

this is also good:
http://www.engineeringtoolbox.com/ou...oise-d_62.html

I need the device to handle sound/vibrations levels that can be as powerful/loud as possible without ruining it. If it can harvest energy from as many sources that include a 180Hz sound/vibration I can harvest energy from many sources.

here's the datasheet of the piezo I am using for more data:
http://eeshop.unl.edu/pdf/LDT_Series.pdf

I can't seem to find like a "maximum ratings table" but basically I can say it's a flexible transducer that can be 'bended' 5mm to either side with no problem. I read somewhere that these type of piezo transducers are not very durable if stretched much.

I want resonance - because in resonance I get maximum voltage for a given sound/vibration power.
If I vibrate the transducer in 180Hz at X power I get more voltage output then at a higher or lower frequency with the same X power(see "Experiment #1 - LDT0 as Vibration Sensor" in the datasheet). It is possible to lower it's resonance frequency by adding mass but then I don't think I will find a common low frequency ambient source for it to harvest energy from.

Again, I want maximum voltage output from this piezo and If I can keep it in resonance I can get high output voltage for longer time(that's AC voltage and I will rectify it and store it in battery/capacitor).

Using an amplifier is not good because the amplifier will eventually be powered by the piezo itself so it's like a system that just uses power but does nothing(a cup with a hole in it, you can put water but it will be wasted). By using passive amplification I can use the voltage from the piezo to power more 'useful' components.

In the end product the piezo is there just to give power so electronic amplification will only do harm, please stop suggesting it.
davenn
#38
May17-13, 06:53 AM
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Quote Quote by Shploop View Post
.............I need the device to handle sound/vibrations levels that can be as powerful/loud as possible without ruining it. If it can harvest energy from as many sources that include a 180Hz sound/vibration I can harvest energy from many sources.

..................Again, I want maximum voltage output from this piezo and If I can keep it in resonance I can get high output voltage for longer time(that's AC voltage and I will rectify it and store it in battery/capacitor).

Using an amplifier is not good because the amplifier will eventually be powered by the piezo itself so it's like a system that just uses power but does nothing(a cup with a hole in it, you can put water but it will be wasted). By using passive amplification I can use the voltage from the piezo to power more 'useful' components.
hi there

you not the first one and wont be the last one to consider harvesting sound to generate an electric current .... it is a topic that comes up on the forum a few times or so a year.

and you will get told the same thing all the others do ......

you obviously dont realise how little energy there is in all the ambient sound that is around you.
its absolutely miniscule !!! just stop and think for a moment how much amplification has to be done to the tiny signal generated by a microphone to make it useable.

even shouting directly into the front of a microphone will generate at best ~ 100-200mV
normal rectifier diodes take ~ 600 - 700mV (0.6-0.7V) to conduct so you cant use them
some Schottky Diodes have a lower conduction voltage. But the point is you are not going to get anything out of them that is useable to charge something or to be stored

You are not going to be charging any capacitors or batteries any time soon.
You cannot amplify it ... as the power required to run the amplifier would be substantially more than what was generated by the microphone ( or other audio pickup device)

there is NO passive amplification of an AC or DC voltage, all voltage/current amplifiers require active components that need power added to the circuit to make them work

Really hate to burst your bubble, but its just not feasable

regards
Dave
Shploop
#39
May17-13, 07:23 AM
P: 24
thanks you, your reply was one of the best and to the point and supports my claim that electric amplification is useless here(as I already said):
Using an amplifier is not good because the amplifier will eventually be powered by the piezo itself so it's like a system that just uses power but does nothing(a cup with a hole in it, you can put water but it will be wasted). By using passive amplification I can use the voltage from the piezo to power more 'useful' components.
that's why I wanted PASSIVE amplification from the beginning...
again by passive I mean concentrate the sound using a non-powered structure(we talked about helmholtz etc...)

to continue the discussion, I know that in some factories in the industry they harvest the energy from large motor and such that vibrate at a certain frequency, so instead of harvesting acoustic energy how about vibration like I already said?

If there is a source that vibrates constantly at a certain frequency(and some decent amplitude) then a device that will attach to it can tap into that energy and say charge a capacitor in 1 Day and use that energy the next day to send some sensor data or other low power application.

what do you say davenn, enough power out there? maybe a car motor?

EDIT:
found someone patented something like I wanted...
https://www.google.com/patents/EP234...=0CDMQ6AEwADgU

https://www.google.com/patents/US200...=0CGQQ6AEwBzgU

also from a vehicle(car...):
https://www.google.com/patents/US793...=0CGsQ6AEwCDge

and also a complete circuit for wireless sensor:
https://www.google.com/patents/US708...=0CEgQ6AEwAzgo

one more:
https://www.google.com/patents/US640...=0CDMQ6AEwADg8

guess I need to find a different way, all has been done...
jim hardy
#40
May17-13, 12:16 PM
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I know that in some factories in the industry they harvest the energy from large motor and such that vibrate at a certain frequency, so instead of harvesting acoustic energy how about vibration like I already said?
Where I worked we would have laughed at harvesting energy from motor vibrations - if it's shaking that bad you better fix it. We equip them with vibration monitors to tell us when they do begin to vibrate so we can replace the bearing or whatever.

However - your enthisuasm is infectious..

and -
One experiment is worth thousands of daydreams.

A loudspeaker is a decent transducer. Build something and see what you get - try a small speaker at the end of a tube it'll just fit inside, in fact make it a telescoping tube you can tune like a trombone. Connect a flashlight bulb and voltmeter across the voice coil.
At 180 hz, a quarter wave is about 18 inches and a half wave of course twice that.

See if traffic noise will excite it. Try it near noisy things like trains and planes.
I doubt you'll see the lamp glow at all unless you're directly under an old unsilenced pure jet plane like Boeing 707/KC135, or if you get lucky a B-52..

You'll prove there's not a lot of energy in sound. That's why one measly watt out of a stereo is too loud for background listening.

Post some pictures -

It would be quite interesting to tune that thing for sub-audible range. There exists something called "Voice of the Sea" caused by wind blowing across waves that's in the range of 7 hz. That's an unwieldy wavelength but you could get creative with resonating chambers (Helmholtz?)
I saw a Nature show proposing that homing pigeons use the sub-audio sound picture of their environs to navigate home.
Shortly before a hurricane sharks around SW Florida have been observed to head for deep water. The birds in my Key Largo neighborhood went someplace the day before Hurricane Andrew. Low frequency audio used to be hard to explore because we can't hear it. Nowadays it seems hobbyists have such powerful toys available that much basic research can be done by amateurs.
Have you access to a spectrum analyzer ? Might be a fun project for today's little microcomputers..there's a FFT library for Arduino.

Take a low frequency sensor to the zoo and listen to the elephants, they are known to communicate with sub audio.

http://www.birds.cornell.edu/brp/ele...nfrasound.html

http://www.theatlantic.com/technolog...igeons/272751/

Have fun !

old jim
Shploop
#41
May17-13, 01:41 PM
P: 24
That's what I am talking about! good reply!
I do like to try things and I do have some access to a spectrum analyzer and the telescopic tube is a very neat idea. I searched for some low power LEDS(a common one is 20mA ~2Vdc) but can't seem to find one I can buy here.

basically I've tested my little circuit and I do charge a capacitor(10uf) pretty quickly by manually moving the piezo and that's even with high drop-voltage diodes(as rectifiers), I got some low-drop high-speed diodes to try.

by the way, these vibration monitors you used are piezo? MEMS? electromechanic?

I will explore any option I can find(that I can make myself) preferably that I can change for my own use and will enable some decent energy output.

I think bio-mimicry is the way to go, nature has got many questions solved before we even asked. I am searching amazon for some good books on the subject, Do you recommend any?

and speaking of animals, I know whales communicate at low frequencies too, about 15Hz, there is a funny story about a whale that sings at 52Hz, they say he is the loneliest whale in the world:
http://en.wikipedia.org/wiki/52-Hertz_whale
jim hardy
#42
May17-13, 02:18 PM
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I searched for some low power LEDS(a common one is 20mA ~2Vdc) but can't seem to find one I can buy here.
I doubt you'll be able to make 2 volts with a voice coil driven by sound. But experiment.


by the way, these vibration monitors you used are piezo? MEMS? electromechanic?
We monitored large heavy rotating equipment. Some monitors were electromechanical velocity sensors(coil and magnet) , some were based on commercial piezo accelerometers, some were induction based proximity sensors that measure displacement.

Since we produced heat at the rate of 2200 joules/microsecond we didn't even think about nanowatt harvesters.

There may be I think an emergent niche market for such gizmos in remote unattended monitoring and data logging applications, but we used battery powered devices. The payoff would be not the energy but the convenience of not having to change batteries. I think I saw mention of that shortly before I retired a decade ago.

Again have fun. This is an amazing age for tinkerers.
Shploop
#43
May17-13, 03:04 PM
P: 24
Well someone made just what I wanted to make... just proves my idea was good...
they use 120Hz, even lower then my 180Hz piezo:
http://www.extremetech.com/computing...omes-to-market
Bobbywhy
#44
May18-13, 05:20 AM
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Quote Quote by Shploop View Post
Well someone made just what I wanted to make... just proves my idea was good...
they use 120Hz, even lower then my 180Hz piezo:
http://www.extremetech.com/computing...omes-to-market
Shploop, you have demonstrated that you are not receptive to experienced scientists and engineers who have advised you here on your proposed project: to "harvest energy from ambient acoustic energy to charge a battery" is not viable. It has been explained that your concept of "passive amplification" of sound waves is faulty, and that, over time, several other posters here on PF have proposed similar projects, only to find them impossible. Have you done a search yet here in this forum on this topic to see how they were resolved?

Your most recent statement above where you claim that "The Bolt just proves my idea was good" is mistaken. In fact, the Bolt in the link requires an ambient source vibrating at around 120Hz in order to charge a battery. That is, a MECHANICAL vibration from a motor, pump, etc. and NOT a sound wave vibration.

Please note: sound waves do carry energy and a tiny miniscule amount could be harvested using a scheme such as you propose. But, (pay attention, please) the charging current would be measured in microamperes and the amount of power would be measured in microwatts. Learn to do the mathematics to calculate acoustic power available in the environments you mentioned. Convert those SPLs (Sound Pressure Levels), given in dB, to units of power (watts). Then consider all the ineffiencies in the conversion process, and arrive at the energy available to store in the battery. You will immediately find this amount is so small that it would be a waste of time to even try it.
jim hardy
#45
May21-13, 08:04 AM
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Nanopower electronics can run on these things. Don't plan on them reducing your electric bill, though.

Here's an industry article with some interesting links :
http://www.designnews.com/author.asp...dfpLayout=blog

Click the image to open a window with a little slideshow of eight harvesting schemes.

old jim
Bobbywhy
#46
May21-13, 05:30 PM
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Quote Quote by jim hardy View Post
Nanopower electronics can run on these things. Don't plan on them reducing your electric bill, though.

Here's an industry article with some interesting links :
http://www.designnews.com/author.asp...dfpLayout=blog

Click the image to open a window with a little slideshow of eight harvesting schemes.

old jim
Hi old jim! Thank you for that interesting article. I saw all eight examples of energy "harvesters" each one innovative and useful!

Observation: None of those eight uses acoustic energy as a source as the OP here has been proposing.
dlgoff
#47
May21-13, 06:16 PM
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Quote Quote by Bobbywhy View Post
Observation: None of those eight uses acoustic energy as a source as the OP here has been proposing.
Really?
When the brass vibrates, it generates electricity.
http://www.designnews.com/author.asp...image_number=3
russ_watters
#48
May21-13, 06:19 PM
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Quote Quote by Shploop View Post
that's why I wanted PASSIVE amplification from the beginning...
You know there isn't enough energy in sound waves to make a useful source of energy, so you want to amplify the energy without inputting more energy. That's called a Type 1 Perpetual Motion Machine because it violates the first law of thermodynamics. https://en.wikipedia.org/wiki/Perpetual_motion

Since it is a violation of the laws of physics, it is not something that can be done and therefore isn't something we entertain discussion of here. Thread locked.


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