Alternative approach to water leak detection

Hi,

It sounds very useful, and I will probably order one when it's on Crowdsupply, or try to build one, to try it out.

Since it is designed for high frequency sounds, perhaps the source code could also be one day extended to detect other anomalies with high freq content too, e.g. maybe glass smashing, or shots.

A big hurdle for adoption would likely be the microphone I bet, but since you have a hardware filter, that provides a good amount of reassurance. However if removing the surround from the mic, or some other quick hack, could cause speech to be sensed (even at low amplitude), you might also want to show things like (say) if the microcontroller doesn't have the resources to capture or forward speech. Probably some customers would also want to be sure the processor could not run unauthorized code. 

Thank you for the comments and questions. Glass breakage and gunshots are examples of short duration, impulse acoustic events. To capture these, the sensor must poll at a rate faster than the anticipated event duration, ie. likely approaching 1 kHz. This also requires the device to spend considerable time in active mode, which will consume power and affect battery life. Sensors are also available for these applications. The leak detector linked here targets persistent acoustics, which means the environmental sampling rate can be many times lower with much longer battery life. So these are really two different applications.

An important design decision was to make speech capture impossible. The microphone is actually part of a bandpass Helmholtz mechanical filter centered at roughly 8 kHz with a Q of about 30. This is a followed by a 4th-order Sallen-Key high-pass analog electronic filter with cutoff at around 8 kHz. Even if the microcontroller was completely hacked, no intelligible conversation audio would ever reach it. A completely open-source approach allows the design to be inspected and verified that it cannot be used for eavesdropping.

Interesting tech.  Could there be a market for it?  Yes.  It's application is very specific, so I'd anticipate a very low volume of sales - well below "stud finder" and "network cable tester" on the spectrum.  I get that almost everyone in the e14 community will have the latter but not a lot of plumbers also do networking.

I base my opinion on "When would I need this tool?"  In almost every scenario I can think of, it would start with an unpleasant discovery of a wet floor and/or a stained wall or ceiling tile.  My unpleasant discovery will pretty much tell me where the leak is - to the degree of accuracy that I need.  Would I expect my restoration company to have such a device?  Absolutely.  I just can't see myself running out to the local big box hardware store to buy one of these once I discovered a leak.

Just my opinion.  I've been wrong about a lot of things in my life.  This could be one.

Thanks for the comments. The intended use case is not as a handheld tool or plumber accessory, which is what I think you're suggesting. It's designed to be deployed as an automated, remote, low-power wireless sensor node. The idea is to monitor areas where people aren't always going to be present to observe the puddles and moisture stains that may signal a leak. Think attics, crawlspaces, medical/dental offices after hours, etc. A tiny leak in my crawlspace went undetected for 6 weeks, caused a lot of expensive damage, and motivated the design.

Do you need a smoke detector if the signs of a fire are obvious?

microphonon said:

Do you need a smoke detector if the signs of a fire are obvious?

Sometimes you do, as Darley and Latane demonstrated in the '70s... 

The smoke filled room study
https://www.youtube.com/watch?v=KE5YwN4NW5o

Update: The Crowd Supply campaign for the acoustic leak sensor was successful. A production run has completed and units are being shipped to backers in 17 US States and 7 countries.