Hi, I have tried using the electret as a suitable microphone to convert sound to electricity. I have tried a number of circuits and ICs and made progress. However, the electret seems to be very weak and barely picks the sound from the surrounding. I tried mirroring the Sound sensor module circuit in the arduino kit. However, it still did not respond. Any advice/help will be very much appreciated.

 

There's rather too much wrong with your circuit to list all the problems. This is how it should go.
A condensor microphone is usually slightly more sensitive than a dynamic microphone.

 

The schematic of the module has no power supply voltage then it does not work. The schematic has problems.
I found a correct schematic.
Why does your microphone connect to a speaker without a preamp and without a power amp??

The module that was posted uses an LM393 comparator, it is not a preamp. It lights the LED when the level of sound is higher than the threshold voltage set by the trimpot.

It does not use a condenser mic that must be biased with 48V, instead it uses an electret mic that has the 48V stored in its electret material and has a Jfet impedance converter that uses a few volts at 0.5mA max.

 

The schematic of the module has no power supply voltage then it does not work. The schematic has problems.
I found a correct schematic.
Why does your microphone connect to a speaker without a preamp and without a power amp??

The module that was posted uses an LM393 comparator, it is not a preamp. It lights the LED when the level of sound is higher than the threshold voltage set by the trimpot.

It does not use a condenser mic that must be biased with 48V, instead it uses an electret mic that has the 48V stored in its electret material and has a Jfet impedance converter that uses a few volts at 0.5mA max.

Thanks for this. The electret microphone is still not reading. I expect to read an output

Hi, thanks so much for your reply. This ypu posted the correct circuit for the LM393 and I appreciate that. However, this is just one of the numerous circuits I have tried in converting sound to electricity using the electret microphone. I added more circuits for you to see. I feel its the microphone that may be the problem. Faraday's law of electromagnetic induction obviously holds with sound and so I believe this should work. Your advice and help will be very much appreciated.

Moderators note : removed the extra quotes

 

What exactly is the object of your experiments? Are you trying to make a circuit that will amplify the signal from the electret microphone enough to reproduce the sound on a speaker? The electret microphone only produces a few millivolts of output and will need a lot of amplificetion to drive a speaker. There are lots of circuits on the internet that will do that.

 

You say you want to convert sound to electricity. What is the electricity being used for? In the Completed Projects thread, search for AAEF.

 

Your schematics of the preamp and power amp had some errors, I show what was wrong.
If the mic can hear the speaker then you will have feedback howling.

 

You say you want to convert sound to electricity. What is the electricity being used for? In the Completed Projects thread, search for AAEF.

It’s being used to charge a battery (no matter how small)

 

What continuous sounds are you using? Screaming or acid rock noises?
The circuit in post #7 produces 2.1V RMS into 8 ohms which is an AC current of 265mA when playing loudly.

The LM386 uses more than half the power of the 9V battery to make heat which is a waste of battery power. So why not use the battery that powers the amplifier to charge your battery?

 

An electret microphone is an electrostatic device and will not generate an output signal unless it connected to a bias supply. The signal it generates is just a few mV at very high impedance, so the amount of power output is far less than that used by the bias supply.
You need to use a microphone needs no electrical input power to generate a signal. A dynamic microphone uses the movement of a coil of wire in a magnetic field to generate a signal but the output is only a few mV. A speaker connected as a microphone would give you a little higher output because the large area of the cone would receive more sound than a typical microphone.

 

A piezo transducer generates a small voltage at a very small current when it is flexed slightly.
Somebody mounted hundreds of piezo transducers on a busy sidewalk and made enough electricity to dimly light one little LED.

 

The TL071 Op Amp followed by an LM386 used in a parabolic microphone or telescopic microphone circuit might be a start.
The parabolic dish concentrates the sound which increases the conversion done with the microphone.
The ear is more efficient than a microphone. An elephant can hear 6 miles away.
https://www.nutsvolts.com/magazine/article/the_big_ear#Sidebar 2

 

If you do the calculations from dB to Pascals to Watts per square metre, you'll soon see how impractical it is.
The base for sound measurements is 0dB = 1pW/m^2 = 20uPa
So at 100dB you have 10mW/m^2.
A typical dynamic microphone like the world's favourite Shure SM58
https://www.shure.com/en-GB/products/microphones/sm58
will give -54dBV/Pa = 2mV @94dB at a source impedance of 300Ω, so the maximum power from it would be 1mV^2/300 = 3.3nW.
The sound flux at 94dB is 2.5mW/m^2
As it's about 40mm in diameter, area 1.25x10^3 m^2, the sound flux reaching the microphone is 3.1uW, that makes the efficiency roughly 0.1%.

 

https://www.bbc.co.uk/news/business-34604842
and look at the date on the article. Do we see the product 6 years later?
I seem to remember it employed a steerable ultrasonic transducer working at 55kHz, which located the phone and beamed ultrasound at it.
Note: cats can hear 55kHz.

 

I’m not

What continuous sounds are you using? Screaming or acid rock noises?
The circuit in post #7 produces 2.1V RMS into 8 ohms which is an AC current of 265mA when playing loudly.

The LM386 uses more than half the power of the 9V battery to make heat which is a waste of battery power. So why not use the battery that powers the amplifier to charge your battery?

At this point, I’m not exactly particular about the efficiency of the product as I am making it produce voltage by using the microphone. Any further help on this will be very much appreciated.

 

So you want to charge the battery using the power of sound? And you're not bothered if the efficiency is less than zero? I'm lost here.

 

It’s being used to charge a battery (no matter how small)

While you could "charge a battery" you would only be using the microphone as a strange kind of switch to decide how much power would be sent to the battery from your power supply.

Though charging batteries with sound is really not practical, you would need to use a dynamic microphone to even begin, which actually produces a tiny current on its own.

Energy Harvesting is the name of the area you are trying to work in and using microphones isn't one of the ways that's used. If for some reason you just want to collect acoustical energy as electrical energy in a purely theoretical way with no practical application, a dynamic microphone and a super capacitor are the two key elements to try.

Your current attempts will never do what you say you want to do.

 

So you want to charge the battery using the power of sound? And you're not bothered if the efficiency is less than zero? I'm lost here.

The foundational theory for this is sound is a form of mechanical wave and when harnessed properly can produce electricity as per Faraday's law of electromagnetic induction. The science is undisputed and this is what I am trying to thrive on by trying it practically. I just haven't been able to make it work yet. Do you agree with the science?

 

Yes, I had looked into the operation of a supercapacitor during the course of this research. I do admit that it may be a game changer, but I also see a possibility in producing voltage using the regular electrolytic capacitors. As for the dynamic microphone, I haven't seen a suitable way to combine it with a model circuit. Thanks for your response in anticipation.

 

The foundational theory for this is sound is a form of mechanical wave and when harnessed properly can produce electricity as per Faraday's law of electromagnetic induction. The science is undisputed and this is what I am trying to thrive on by trying actually doing it practically. I just haven't been able to make it work yet. Do you agree with the science?

I am afraid that while you have the idea right, and a dynamic microphone is, in fact, a direct transducer of acoustical mechanical energy to electrical energy, there is a lot of other science you have to consider when you try to use that electrical energy for something.

Do you have any idea how much energy is in the sound waves you will be intercepting to convert? Maybe calculating that, then calculating the demands of any storage system (losses, etc.) and the demands of any application would be helpful.

You will be producing vanishingly small amounts of electrical power and they will be practically useless.

Do you just want to see it happen, or do you hope to use it for something. If you just want to see it happen, you could probably manage to charge a capacitor a tiny amount over a long period with a constant and very loud sound.