Could not resist to run some experiments. A big bass speaker, when tapped softly (8 Ohm) gives about 1.5 to 3 Vpp.
Not quite enough for a LED... So found an old mains transformer 240 / 9 V, connected the speaker to the 9 V side, and scoped the 230 V side. now THERE is energy! Connected a white LED. Tapping the speaker flashes it brightly.
Did some other test without transformer too, BAT rectifier, JFET oscillator, even that I can get oscillating.
So tap the environmental sound, much better than environmental RF.
Usenet patent, all rights reserved Jan Panteltje 2015 idea for sale ;-)
To give you some idea: Dropping a TO220 transistor from 5 cm anywhere on the speaker cone flashes a white LED, clearly visible in bright sunlight.
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Setup, did not even bother to disconnect secundary rectifier in DC adapter I borrowed transformer from:
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So this makes it complete, working prototype:-) LOL
Some reality checks regarding audible frequencies (> 20 Hz). The threshold of pain is about 120 dB SPL corresponding to about 1 W of audio power into a square meter.
Ear protection is required above 85 dB SPL for full day work, which corresponds to less than 1 mW of acoustic power.
The conversion efficiency from electric power to acoustic power in modern woofers is not very specular, so I would assume that the conversion efficiency in the opposite direction is not any better. Thus the available electric power is quite low.
What your experiment shows is that the speaker might be usable for converting subaudible vibration to electricity.
On a sunny day (Sun, 12 Apr 2015 18:59:21 +0300) it happened snipped-for-privacy@downunder.com wrote in :
Exactly, say in a room when you open or close a door the cone already moves a lot. I had to calibrate some stuff in an engine room of a big ship once, the diesels running, we had to communicate with sign language almost, and it was moored in the harbor and just running stationary... There are plenty of situations where the low frequency sound level is very very high, wind outside works great here, and jet engines testing is an other.
Also any movement if the membrane is big enough, could be flexible back side of a cellphone. Of course cellphones have the asymmetrical 'vibration alarm', I am sure that could be used to get some power from user motion too. And then there is the car with the boom boom -, and the average boom box .
Energy harvesting from sound is obviously the future, and 'more research is needed' (M dollars) blah blah, but it is fun even like this.
Lol, that's the mechanism in a self winding watch... e.g. a self winding phone, lol Once you quantify the energy available you will realize there is no way to power most user devices. Try powering a clock... that is practical.
I want a sound guided missile for that particular issue.
Obviously the future? Not sure what that means. The applications are relatively sparse. Your engine room app is already being exploited for remote sensors which would be hard to replace batteries in. So this is the EH of the present.
use something far more efficient & higher impedance, and you might get that coveted microwatt. With that you could send a temp reading to a host once or twice a year.
Might work in the tropics with daily thunder storms. You would have to install your audio transducer in a high tower that gets hit daily :-).
It would be much easier to use a current transformer around the lightning arrester grounding cable.
Anyway, if you can power up some sensor with microwats, you still have to transfer the data somewhere else to be usable and this also going to require some real power. For wireless networks, there is the inverse square rule and for wired connections, there is always the SNR issues, usually just inverse dependency of distance.
On a sunny day (Sun, 12 Apr 2015 10:56:06 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :
Well I also tried to power this, the JFET nicely started oscillating:
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I tried by rectifying the speaker output directly with a BAT xx (don't remember) Schottky, and also without the power MOSFET, It only needs a few mV and I still had that laying around. The 470 uF cap needs to be smaller, it does not charge enough in a single tap on the speaker. But it oscillates! in bursts! at several kHz, enough to do a measurement and send data on every tap! Then I tried it with simple AC (no diode, some worked some did not). Anyways ideal would be a small 10:1 audio transformer (I have some in use in an other project as HV transformer (Geiger counter)), that gives you in the 5 to 10 V range at more current than the about 1:25 mains transformer I tried, better frequency response (better iron) I think too, those are very small transformers (from conrad).
So, microwatt sensors, no problem. Proof of concept works!
It is probably old hat, I am sure somebody must have tried all that ages ago, just that we now can make very low power stuff that makes it interesting. As oscillator is working, I could send a QAM modulated signal with temperature no problem with this, microwatt PIC temp sensor already on my site:
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or power scope_pic from it, leave out the LCD (power hungry) and send data via RS232 or RF:
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or some thermo couples:
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But in that case you can also power from a thermocouple, see top link, lighting_a_LED_with_a_candle I think this is already done in industry.
You'll get more output if you drop big rocks on the speaker.
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John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
150-12" woofers across the frontage of my property on a 5 lane busy road. Loud motorcycles alone will power my air conditioner! Or not. Mikek PS. Still waiting for LENR.
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We run about $130 per month for electricity and natural gas combined. We don't have a/c, the heat and clothes dryer and cooking are gas, and most of our lighting is CF or LED. The cost of electricity is graduated, from 10 cents per KWH up to 30, depending on how much we use. We are a bit into the top bracket.
We let PG&E do the energy harvesting for us.
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John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
OK, it was tongue in cheek. My bill runs $230 to $520 a month, but I have my business included in that. I might be able to use some of Mr Money Mustache's ideas! Mikek
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Yep, that's the big problem with acoustic coupling in air. Impedance mismatch is so bad that you can't get much energy out.
Harvesting energy from water waves works because the match is so much better and the mass being moved around is huge.
One might argue that a windmill is an impedance matching device and a frequency multiplier with a HUGE multiplication from almost DC to something useful.
Try one of the "shaker" flashlights. You have to move that heavy magnet a LOT to generate useful power, and you've got very tight coupling to the energy source.
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