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TEMPERATURE
SENSOR
The
temperature sensor module is another simple design.
With the high level of hardware integration on
the MC13192-SARD PCB, all you need is a National
Semiconductor LM34 precision Fahrenheit temperature
sensor.
The
measurable temperature range is 0° to 256°F. The
upper limit is the result of the 8-bit data field
in which the temperature is transmitted to the
base. And although the LM34 can measure below
0°, this requires a negative supply. That would
have complicated the design so it wasn’t necessary
for the application (to measure the proper operation
of an HVAC system or watch for temperatures that
may cause water pipes to freeze and burst). Measurement
from 0° to 256°F is sufficient for these purposes.
Connections
for the LM34 sensor are shown in Figure 3. Like
the water level sensor, 5-V power for the temperature
sensor is obtained via a connection to the TP104
on the solder side of the MC13192-SARD PCB. Ground
is obtained from the J101 BDM port pin 2. The
signal is connected to the ATD2 input on pin 3
of J105.
(Click
here to enlarge) |
Figure
3—The temperature sensor’s layout is fairly
simple. The LM34 is connected to the MC13192
SARD PCB’s 5-V supply, ground, and analog
input. The pressure sensor hardware is complete. |
