Quiet Water Alarm

Project Number: 70

OBJECTIVE: To sound an alarm when water is detected.

Description: Sometimes you may want a water alarm that can be heard but not loud enough to be annoying or distracting, so let's make one. We'll also put a light on it that could be seen in a noisy room, in a real application you could use a powerful light that would be easily seen. Build the circuit shown but initially leave the jumper wires outside the cup. Turn on the slide switch (S1); nothing happens. Place the jumper wires into a cup of water and an alarm sounds and the light comes on.