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Liquid Sensors,
Water Sensors,
Water Level Monitors
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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. |
| The 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. The 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. |
One 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.
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DRAWING HERE - add PDF LINK |
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Liquid Sensors,
Water Sensors,
Water Level Monitors
Master Category
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