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Water Flowing in Pipe Indicator
-- July 6, 2009
|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.
Drawing only 6uA, the whole circuit is powered by a lithium coin battery, which
should power the circuit for many years.
piezoelectric wafer is carefully sandwiched between a plastic enclosure, housing the
battery and electronics, and the water pipe, using a nylon cable tie to apply pressure.
A bit of epoxy putty helps the assembly to conform to the pipe and couple more of the
vibrations to the piezoelectric device.
single resistor R7 defines the vibration sensitivity. The resistor value can be
selected so very low flow rates can be detected or ignored. After the first
voltage comparator circuit, a 1 second filter circuit is installed. This forces
the vibrations to be maintained for at least that long before the circuit changes state.
This filter circuit helps to ignore pipe impact noise.
application for this circuit might be for an irrigation control system. A positive
signal from the flow sensor could be used by the control system to confirm that water is
flowing. In another application, the circuit could activate an alarm should
flowing water be detected when it should not be flowing.
Click on Drawing Below to view PDF version of Schematic