Thermal Sensor Subsystem Requirements
and
Functional Description
Subsystem Requirements
The goal of this assignment is to design and build the thermal sensor subsystem
for YODA. These are the
requirements for the subsystem:
-
The output should be an analog reading which depends on the temperature
-
Interface requirements: The thermal subsystem must have the following pinout
in a male DB-9:
-
Ground
-
+ 5 V
-
+ 8 V (if needed, otherwise unconnected)
-
Battery unregulated voltage (if needed, otherwise unconnected)
-
- 5 V (if needed, otherwise unconnected)
-
Output analog signal
The thermal sensor must determine whether the temperature is hot, normal
or cold. The sensor must be readily accessible from the outside so that
the satellite hardware is not damaged if an ice cube or heat gun were applied
to the sensor.
Functional Description
The thermal sensor is a reverse-biased Zener diode (LM335Z)
whose behavior is temperature-dependent. The sensor is placed in series
with a 4.7 k resistor creating a simple voltage divider. The output of
the sensor is an analog voltage signal measured across the diode which
depends on the temperature according to the table below. This reading is
connected to Pin 6 of a male DB-9 connector.
|
Temperature
|
Voltage
|
|
Cold
|
2.83
|
|
Normal
|
2.94
|
|
Hot
|
3.60
|
The remaining pin assignments are as described in the
Subsystem Requirements.
Links to Subsystem Documentation
YODA