Water Sensors/Detectors Circuits

• Electrodeless Water Level Monitor
  This system operates much like a classic float switch but without any moving parts.  The illustration shows how a system using two copper coils sealed inside a plastic pipe, can detect the level of water outside the pipe.  Whenever the water level is lower than the upper coil, no signal is coupled between the coils.  Once calibrated, this technique might also work on the outside of a plastic water tank.  (added 7/06)

• Water Flowing in Pipe Indicator
  The vibrations associated with water flowing through a pipe are picked up by an inexpensive piezoelectric wafer.  The signal from the wafer is first boosted by a micropower transistor amplifier and then fed to an ultra low power voltage comparator.   When the vibration signal has sufficient amplitude, a FET transistor switch is activated.....