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Motorola Sensor Device Data
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WATER LEVEL DETECTOR
A single probe connected directly on the detection pin of the
Alarm IC provides a portable solution for water level detection.
When liquid enters in contact with the probe, the resistor
between the detection pin and the supply drops from an open
circuit to a measurable value. With an appropriate choice of
bridge resistors, the presence of liquid will trigger the
comparator. The logic level can be connected to any
monitoring system allowing pump starting, floodgate closing
and others. This simple system is useful for numerous
applications, such as swimming pool water level alarms,
defrosting water level detectors, and in–house flood alarms.
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+
VSUPPLY
PROBE
P15
P13
LOW BATTERY
DETECTION
ALARMIC
LED
PIEZO–HORN
LOGICAL
Figure 3. Water–Level Detection Example
MOTION INDICATOR
The Alarm IC can be used to detect motion and can be
integrated into products, such as an ordinary clothes iron,
where this is critical. Used with a low G accelerometer and a
few logic components, the device can signal the user that
there is a risk of clothes burning during use and that the iron
must be shut off from the AC power after use. At the output
of the accelerometer, a simple peak detection circuit is
required to keep the signal active long enough.
When no movement is detected, the output comparator is
low and the counter starts. A first “beep” is heard after a few
seconds to advise that there is a risk of clothes burning. If no
movement is detected, the counting continues and drives a
flip–flop connected to pin 15 of the Alarm IC. The alarm is
triggered and will continue on until a new movement is
detected, resetting the counter.
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+
VSUPPLY
L
A
P15
LOW BATTERY
DETECTION
ALARMIC
LED
PIEZO–HORN
LOGICAL
Figure 4. Motion Indicator Example
LOGIC
BLOCK
INCLUDING
COUNTER
GATES
FLIP–FLOP
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FILTER MONITOR
An ideal solution for air cleanliness control is provided when
the Alarm IC is directly connected to an MPX5000 series
pressure sensor. This sensor family is compensated in
temperature and has its output signal directly exploitable
(internally amplified). Therefore, the sensor can be connected
to the detection pin of the circuit without any additional
component. When a certain level of dust affects the efficiency
of the filter, a differential pressure is measured and the Alarm
IC comparator is triggered.
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+
VSUPPLY
MPX5XXX
SERIES
P15
P13
LOW BATTERY
DETECTION
ALARMIC
LED
PIEZO–HORN
LOGICAL
Figure 5. Pressure Change (Filter) Example
F
Freescale Semiconductor, Inc.
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