The end of the year is rapidly approaching and there’s a good chance you have a slowly dying tree in your living room. Help it hold on a little longer by using [Eric Ayars'] Christmas Tree water monitor. He’s built a sensor out of a piece of strip board. Three bus strips on the board allow for a variety of alerts. When all three are submerged everything is ok. When the two longer traces are still under water but the third is not an LED will blink to let you know it’s time. If you don’t pay attention and there’s no water left, a piezo buzzer makes noise until you add water (or the coin cell runs out of juice).
This project centers around an ATtiny85 that [Eric] programmed using an Arduino, one of the methods we covered in our AVR Programming Tutorial. But if this simple circuit isn’t high-tech enough for you, we saw a similar method last year that will send an alert to your iPhone.