Can you build a better (dumb) leak detector?

[joeyjoejoe]

So, obviously these things are quite cheap, approaching 5CAD on AliExpress.

Some potentially better variants are hitting closer to 8CAD on Amazon. (https://www.amazon.ca/Instapark-IN07A-Water-Sensor-3-Pack/)

I'm wondering if I can make a better one.

I'm envisioning a tiny PCB - bottom side is exposed traces to detect. Top is a tiny MCU (Attiny45/85?), piezo/buzzer of sorts, and battery.

For the 555 crowd - MCU, as having low battery detection and beeps from a simple ADC would be imperative.

The battery becomes a bit of a challenge:

- CR2032 could last ages, until it needs to beep for 8 hours (assuming a leak immediately after leaving for work)
- 9V makes the device rather thick
- AA would allow for rechargeable, nice on the wallet, but two minimum to run MCU at ~2.8V.

Another potential challenge is obtaining a good volume of beeper for low cost, and at what voltage does it need to be driven.

Of course, it's a fun project, which is always a bonus!