0
\$\begingroup\$

I'm searching for a sound/audio sensor with ultra-low power consumption to detect the presence of a really loud noise (100dB+). The controller runs on battery and there is no option for a different power supply.

For me as a non-expert there seem to be two major types of sensors:

  • Electret microphone (with potentiometer): Here I had a battery life of not more than a week. But the device works as intended due to the right sensitivity.

  • MEMS microphone: These do look like the real power savers but the byproduct seems to be some way too high sensitivity. I read about that Vesper VM1010 (https://vespermems.com/products/vm1010/) which looks like a perfect fit (if the noise threshold can be set high enough) with about 10us current but as a hobbyist I'm totally unable to do anything with PCB and I can not find any (cheap!) breakout boards.

The common use case for sound sensor seems to be the detection of (very) low noises and I have been searching for a while now to find my product. And yes I even considered to design my own PCB circuit but I have a lack of electronic knowledge and I just don't want to believe that there isn't any smart solution for simple people.

I really appreciate any help or suggestion you can give. Thanks a lot!

\$\endgroup\$
1
\$\begingroup\$

Try using an ordinary loud speaker as a microphone. And it doesn't require any applied power.

The moving coil and magnet generate a voltage.

Loud speakers come in a variety of low impedances.

\$\endgroup\$
  • \$\begingroup\$ Wow! Thank you so much for that great idea! Can you provide an example of a speaker that may be appropriate? (Or simply some tags I could go for) \$\endgroup\$ – MaxPower Mar 31 at 16:24
  • \$\begingroup\$ Search here on EE stack exchange for "speaker as microphone". \$\endgroup\$ – Marla Mar 31 at 16:28
0
\$\begingroup\$

The VesperMems product seems to be ideal for your requirements; amplitude detection, variable threshold and ultra-low standby power.

All you need is about 80 dB of attenuation, across the whole audio frequency which is harder than it sounds ( pun intended ) as lots of materials behave more like a low pass filter, so you can still hear the bass.

This may require some further research on your part to identify the spectral sensitivity of 100dB which to humans becomes an almost flat response. enter image description here Courtesy WIki

When you use a speaker or microphone, you can imagine how loud it is when you tap the diaphragm. So protection from these near-field vibrations must be isolated or prevented.

Acoustic Pressure is logarithmic (dB SPL) meaning it spans many decades of power levels and choosing a calibrated 100dB can be done, but this is another task for you to define, as well as defining the minimum event duration and stretching the event to stay ON or to some interface device.

So there is more to your design specs than simply choosing the sensor.

\$\endgroup\$
0
\$\begingroup\$

A piezo transducer might suffice to provide a voltage needing no amplifier. However, these are high-impedance devices, and to preserve the large output voltage, it must see a load resistance that is large.
As a test, a piezo element was measured with a 10Mohm oscilloscope. A "hand-clap" was the source of loud noise, about six inches away. When changed to a 1Mohm load, results were similar. It produced the following voltage, whose peak-to-peak maximum amplitude reached about six volts:
hand clap into piezo: volts vs. time This particular piezo transducer was surrounded by a plastic shell, which provides a large resonant peak at about 3.4 kHz. That results in a sinusoidal wave that swings above and below zero volts. There are about seven cycles within each (dotted) division of the oscilloscope scale (0.002 seconds per division).
You could quite possibly hose this transducer up to a microcontroller's analog-to-digital converter directly - no amplifier needed. A few large-value bias resistors might be necessary to establish a known DC voltage at the input pin.

This might even work hosed up to a CMOS or HCMOS logic gate input.

\$\endgroup\$
  • \$\begingroup\$ I have a remote control for my house fan, and this is how it works. Actual end-user product. You push the switch, and it goes "snap". No batteries. \$\endgroup\$ – gbarry Mar 31 at 19:03
  • \$\begingroup\$ Piezo may produce enough high voltage, for long enough time, to overheat the protection diodes on the MCU's ADC input. Place a 100Kohm resistor in series. \$\endgroup\$ – analogsystemsrf Mar 31 at 21:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.