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Jameco Electronics Puzzler: Water Detector

By Forrest M. Mims III
Water Detector Schematic

What's the Missing Component?

The Ultra-Simple Sensors Company assigned its engineering staff to design a circuit that would trigger an LED when a few millimeters of liquid water is present in a basement or boat. The winning circuit is shown in the image above– less its sensor.

What is the liquid water sensor concealed behind the puzzle piece? Before revealing the answer, here are some hints:

The LTC1050 in the image above is connected as a comparator that switches on an LED when liquid water is present at the sensor. Otherwise the LED is off.

What is the water sensor behind the puzzle piece?

Click here for the answer.