MPXM2102AS datasheet(663/670 Pages) MOTOROLA

663 / 670 page

AN4009

4–71

Motorola Sensor Device Data

www.motorola.com/semiconductors

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.

–

VSUPPLY

PROBE

P15

P13

LOW BATTERY

DETECTION

ALARM IC

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.

–

VSUPPLY

P15

LOW BATTERY

DETECTION

ALARM IC

LED

PIEZO–HORN

LOGICAL

Figure 4. Motion Indicator Example

LOGIC

BLOCK

COUNTER

GATES

FLIP–FLOP

–

INCLUDING

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.

–

VSUPPLY

MPX5XXX

SERIES

P15

P13

LOW BATTERY

DETECTION

ALARM IC

LED

PIEZO–HORN

LOGICAL

Figure 5. Pressure Change (Filter) Example

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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