How to Build a Simple Single Transistor and Paper -- Water Leak Detector Circuit

Video demonstrates how to build what I refer to as a single transistor and paper water leak detector. It works off of the same principle as a simple transistor touch switch circuit except it uses a piece of paper that once wet serves to close the path and provide continuity between the "touch" contacts in turn switching on the transistor and piezo buzzer. In essence, it uses a piece of paper, the functionality associated with an NPN transistor, and the highly annoying sound produced by a piezo buzzer to provide one with an early water leak detection / warning system --- hopefully before one discovers such via wet socks in the middle of the night!

Parts List:
-- NPN transistor (an 2N2222 was used in the video but a 2N3904, or B547 should work the same).
-- Piezo Buzzer (a RadioShack # 273-0059 was used in the video)
-- 1K resistor (X 2)
-- 1N4148 diode was used in the video and will work fine. A 1N4001 would work as well. But if you really want to add that little extra added protection for the transistor, then a faster switching diode like, e.g., a Schottky 1N5817 - 1N5819 would be even closer to ideal. Essentially, like in the case of relay coils, you just want to re-route any inductance generated when the piezo buzzer is switched off away from the transistor. The more quickly such can be done, the overall better for the transistor. Standard diodes work, schottky types will simply work a little faster.
-- alligator clip jumper wires (or some other reasonable means of connecting the piece of paper to the circuit)
-- power supply (will be relative to the piezo buzzer used, 6V battery pack was used in the video)
-- 22-24 gauge wire

If you liked and/or found this video to be helpful please consider clicking Like, subscribing to my channel, and checking out more of my videos. Either way, thanks for watching!

Disclaimer:
While I am more than willing to use this circuit as a means of early water leak detection /warning under my sinks, no warranty for your cabinets, water damage, corroded batteries, etc., is expressed or implied if one builds and implements this circuit and still ends up with soggy cabinets, etc. It's also worth noting that the circuit will only serve as an early warning system if one is home to hear it sound off, if the batteries are not dead, etc. So, build and use it as your own risk.