Our final project involved the design of a fully functional, multi-purpose
digital thermometer. This was our attempt at producing a portable device that
could be widely used for a variety of different purposes. For example, think
of the many situations where the precise measurement of temperature is of high
importance. Temperature control and monitoring is important in homes for the
comfort of its occupants... it is important for gardeners who want to carefully
monitor the atmospheric conditions within a greenhouse... it is important in
ensuring the correct operation of various electronic devices where many components
may have a sensitive dependence on temperature.
Furthermore, our portable digital thermometer could be valuable as a scientific tool in the laboratory. Its ability to accurately measure temperatures to within .1° in FOUR (yes, count them, four!) temperature scales (Fahrenheit, Celsius, Kelvin, and Rankine) adds to its functionality. Just think, no need to go to a table anymore to convert a temperature you just measured to another scale! As a household device, our multi-function digital thermometer is useful for its ability to carefully record and store the extreme temperatures reached in its environment. By simply pressing the appropriate button on its user interface, you can easily display the maximum or minimum value recorded.
Likewise, our digital thermometer comes equipped with an alarm feature which allows the user to program a specific temperature range. This is accomplished by entering lower and upper bound temperatures via four push buttons on the user interface. When the temperature recorded by this device crosses one of these boundary points, the "alarm" is triggered by flashing a message (HOT! or COLD) in the display window. Additional functionality has been added to this feature regarding the options for changing these boundary temperatures, which will be explained later.
In addition, whenever the ambient temperature reaches either of the extreme "alarm" temperatures, one of the port pins goes active low (i.e. turns ON). PortB is low when it is too hot, and PortB is low when it is too cold. The user can easily interface with these two port pins to add any kind of functionality desired.Overall, this feature, in particular, greatly extends the applicability of our digital thermometer. The temperature-range interrupt feature could enable this device as a control unit which drives an air conditioner, fan, or heater in a climate controlled environment... or it could send a control signal to turn on a sprinkler system if the upper threshold is passed. The possibilities are endless!