Will this work fine?

Discussion in 'The Projects Forum' started by s2pk, Dec 18, 2010.

Jul 10, 2010
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hello forum, I am planning to work on a project " generation of electrical energy from noise" I this it may work for airports, noisy factories, busy shopping malls. The real world example of this is mic, which convert sound waves (mechanical waves) into electrical pulse. The device used for converting mechanical waves into electrical is known as transducers, i saw on a forum that 120db= 1 watt
though this project will not work for every place but as I said this may work for airports, shopping malls etc. could anyone guide me how to make circuit for this project

2. Wendy Moderator

Mar 24, 2008
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Welcome to AAC.

What would the signal be used to power? We occasionally have threads for similar requests, yours is probably the first practical one I've read yet, as you have specified an energy rich environment. Too many people think they can get free energy from low energy environments.

One of the problems with noise is it generates very low level signals in terms of voltage. This means components like diodes that have a voltage drop have real problems harvesting this low level signal. Shottky diodes are better than most diodes, as they drop less than a germanium diode, but loosing 0.2V to voltage drop is still significant.

My thought is a simple transformer to convert this into a higher voltage, then use Shottky diodes feed a storage device like a capacitor. I don't think you will get very much power, but transformers are just about the only device that approaches 99% conversion efficiency.

The other problem is speaker energy conversion. I can't help you with that, but it seems to me you may look for a speaker design that covers a lot of acoustic area (large speaker cone), uses a cone that is extremely lightweight (a large amount of energy is absorbed right there), and may be tuned for where the major frequencies are.

There is where the work lies. Maybe a large wall with the coil and magnets attached, where the inertia of the magnets interacts with the lightweight coil? Seems like there might be good ground for invention there.

Last edited: Dec 18, 2010

Jul 10, 2010
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yes using a transformer would be a better choice for me as well, and obviously the diaphragm of the transducer should be pretty enough to gather more and more noise but here I want to tell u something, I have currently planned to get only few watts of power which can charge up mobile battery or which can lighten few LED's. I saw a device called SONEA (searh google "SONEA Converts Sound to Energy") doing the same job, can u design a circuit for such device.

4. Wendy Moderator

Mar 24, 2008
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Nope, I have a full plate of my own projects. It's your idea, run with it!

deanluna likes this.

Jul 10, 2010
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How should I start designing the ckt, need some tips from u

6. kubeek AAC Fanatic!

Sep 20, 2005
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first you need to specify the parameters of the source. What voltage, current and frequency will it generate?

7. SgtWookie Expert

Jul 17, 2007
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There was an idea for using piezo buzzers for harvesting energy from noise published awhile back in Design Ideas.

I've attached a PDF that contains the article; it starts on the 4th page (page 94).

• Design Ideas - 6541376 - Piezo energy harvesting.pdf
File size:
360.6 KB
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31

Jul 10, 2010
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suppose my requirements are 5v, 0.89 A, 60hz then how I would start designing it?

9. Kermit2 AAC Fanatic!

Feb 5, 2010
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Backwards.

You have given the choice output for your device. What can produce that output?

When you answer that you ask what does the output device need for its input?

Does this input exist in the environment, or will you have to create it from another input that exists in the environment.

Block diagrams. Logic flow within each block as it performs its function.

Jul 10, 2010
77
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kermit the device which I have planned to create must give me the following output, don't make fun of me, i haven't worked practically on such project before nor I've designed a ckt before

11. Kermit2 AAC Fanatic!

Feb 5, 2010
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I'm not making fun of you.

YOU need to do lots and lots of research on the devices currently available. If you want to build this thing, then YOU must start gathering the info together and thinking about how they work and might be connected together.

Doing a block diagram and logic flow chart does not require you to know any electronics or circuit design.

You are using a square box to represent a circuit. Inside the box(or on separate sheet of paper), you break down the logical function of that 'box'.

For a power supply the box would have an AC input, a DC output, and a description inside saying what method of conversion you want to use. Diode rectify, or switch mode conversion.

WE make suggestions about alternatives to your choices, or whether those choices are correct or not.

we will NOT do the work for you.

12. kubeek AAC Fanatic!

Sep 20, 2005
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I was not asking about the requirements, but rather about what kind of source you have available. And frankly, getting 4.5W of stable output from this kind of device is impossible (ok maybe not impossible, but surely not worth the trouble).

4.5mW maybe yes after a lot of designing, 4.5W no. You would need to have a big wall made of such devices to get that kind of power. Not only is the conversion process gonna be very inefficient because of the low voltage and current available in the first place, but the greater problem is that there just isn´t enough energy in the sound waves to start with.

On the electronics side, unless you can get say 2Vpeak from the "microphone", you will need some form of synchronous rectification, which will require external source of higher voltage like batteries. Those can be later recharged by the produced energy, but as you can see this adds a lot of complexity and lowers the efficiency.

13. kubeek AAC Fanatic!

Sep 20, 2005
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Hope this is the sonea you were talking about. If you read the comments below you will see it is a CONCEPT DESIGN, not a working stuff. The claims about how much energy it can gather are simply ridiculous, he is even mixing MW with MWh.

14. kubeek AAC Fanatic!

Sep 20, 2005
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Just another thought, I am sure you have seen the "eternal flashlights" which you charge by shaking a pretty big magnet through a coil inside. AFAIK there is a 1F 5V capacitor to store the energy of 12.5J inside, how long does it take to fully charge it? I would say about 4-5 minutes of vigorous shaking. How much power are you generating by that? 12.5J over 300 seconds is cca 40mW.

Now lets say it is just 20% efficient, but I think in this case it well could be much better. That means you are generating with your hand something like 200mW.

Now you want to get 4.5W harvested from sound which is orders of magnitude less energetic, probably in a portable form.

I don´t want to discourage you from this goal, I just want you to see the whole thing in a more realistic way.

15. kubeek AAC Fanatic!

Sep 20, 2005
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My last note: I just found out how it is for real, obvously the area that you are using to harvest makes a difference. So the real equation is 120db SPL = 1w/m$^{2}$, one watt per square meter. This brings me to the original thought about a big wall, i was thinking in terms of 5x10m which seems pretty close, as 50m$^{2}$ subjected to 120dB SPL with 9% efficiency will generate 4.5W.
http://www.sengpielaudio.com/calculator-soundlevel.htm

ETA: Not sure if you are familiar with dB, but this also means that just 10db less, 110dB SPL makes only 0.1W/m$^{2}$.

Last edited: Dec 18, 2010
16. thatoneguy AAC Fanatic!

Feb 19, 2009
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This is an interesting concept. It will need to be physically huge, such as the height and length of a room exposed to the sound.

You will want to find the peak frequency of the noise in the environment. Such as 500-1kHz for voices, under 100Hz for jet engines (though many higher harmonics are produced), etc.

This will allow you to create the correct size membrane to vibrate with the sound, usually a function of wavelength. A very small transducer will only respond to high frequencies, while a very large one will respond to low frequencies.

I would suggest on concentrating on lower frequencies, as they have more "power" than high frequencies, in this case, volume of air moved/SPL. This and the atmosphere are why you can hear the subs of a car stereo long before you can hear the midrange or higher sounds. Low audio frequencies also penetrate walls, sometimes by shaking them slightly, think jet engines, car stereos, fireworks, gunshots, etc.

I'd imagine a very large Piezo or a high end sub with the spider (inner cone dampener) and winding redone to optimize reception rather than production.

An off the shelf speaker will produce a few millivolts@very low current(microamps, <<1mA) when speaking into it, so it can be used as a crude microphone, but you will need to tune the idea a lot more with actual data (not just my guesses above) for the best electrical output for a given frequency, membrane, and coil/piezo.

17. R!f@@ AAC Fanatic!

Apr 2, 2009
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I don't think there is a practical approach to this concept.

18. Wendy Moderator

Mar 24, 2008
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Even in a noisy environment I suspect you would do good to get ½W. A lot can be done with ½ watt though, so that's OK. Most people radically over estimate the amount of real energy in sound though, the device linked to in post #13 is totally bogus.

Basically is an offshoot of the HHO crowd, the urge to get something for nothing is very strong. The OP specified an energy rich environment, but I suspect he is over estimating the amount of energy harvested by a huge amount.

19. wayneh Expert

Sep 9, 2010
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And there's the rub. Many newcomers to solar energy lose their enthusiasm when they learn how "diffuse" it is, at "only" ~1kW per square meter. With photovoltaic efficiency at ~10%, that means they can get get no more than about 100W/m2 under ideal conditions. The economics of state-of-the-art solar technology is not quite competitive with traditional sources, for most uses.

Audio energy at 120db is 1000X more diffuse! That's why you don't feel it warming your clothes or skin like sunlight. And, I'm not sure how efficiently it could be harvested. It may be fun to ponder clever ways to do it, but my hunch is that 10% recovery would be wildly over-optimistic. That means you'd need something that is both really big AND really cheap to have a chance of catching up with wind or solar economics. That's a tall order.

I'll bet there's more power to be tapped in the bottom of your shoe than you "hear" all day long.

20. thatoneguy AAC Fanatic!

Feb 19, 2009
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An easy proof of concept would be to build a sub enclosure, add 2 12" drivers, one powered at 100W RMS at the resonant frequency of the sub (which the enclosure should be tuned for). Drive only 1 sub.

The second sub would be a "passive radiator", of sorts (used for designing enclosure). Bring out wires from the unpowered sub, and measure what power is generated. This will give you a pretty good idea of the amount of power needed to produce any level of usable energy. Even with "direct coupled" sound.

One of the bigger/biggest problems is that air is compressible, so if your 'acoustic alternator' doesn't move freely, nearly all of the energy will compress against the cone rather than move it.