This Tutorial is Retired!
This tutorial covers concepts or technologies that are no longer current. It's still here for you to read and enjoy, but may not be as useful as our newest tutorials.
H2OhNo! is a water sensor alarm. When water is detected across the sense pins an alarm goes off and an LED starts blinking. If you've ever had a water heater explode or tried to create submersible electronics you know how important it is to be able to detect when water is around! You can buy one here.
Underneath the default function of H2OhNo! is a small but powerful development board for the ATtiny85 microcontroller. The board includes a buzzer, LED, a coin cell battery, and the ability to detect analog and digital sensors. This mixture of create a great low-cost tool to learn how to program and how to sense things!
Please note that this kit is not a professional water sensor kit and should not be used in crucial or life support applications. It's a great educational kit and can be used for a large number of applications including sensing when water has gotten too high or two low (like in a fish tank), or it can be programmed to detect an analog voltage and turn on an LED when the voltage has gotten too low (like a low battery indicator).
Before going further with this guide, you should be familiar with the topics covered in these tutorials: