Description
Purpose: You are to design a thermometer with a web interface. The “design” is a set of
documents that describe how to make this device. Accompanying this design is a prototype that
demonstrates that the design works.
This design must satisfy a set of exacting requirements, as laid out in this document. Some of
these requirements specify the expected functionality and performance of the design and some
are mechanical specifications. The primary challenge of this project is to analyze the
requirements carefully and create and implement a design that satisfies all of them. As you
read through this document, you may experience some uncertainty about the meaning or
interpretation of certain requirements. It is important that you get all such uncertainties clarified
before you finalize your design.
This assignment should be completed in “rapid prototyping” fashion, with tangible results
expected early on. With this design technique, the first prototype may not work quite right, or
fully implement all functionality, but will work in some fashion. After the first prototype is
working, then features are added or designs are reworked to meet all the requirements by the end
of the project schedule.
Requirements:
1. General Description: This device consists of four separate assemblies:
a. A computer (PC or other desktop or laptop) used for user interface, display, and control.
b. A thermometer sensor, at the end of a 2.0 +-0.1 meter cable. This should be a nice
mechanical construction, capable of bouncing around without breaking. The sensor
should not be damaged when placed in ice water.
c. A third box containing, at minimum, a display (e.g. a set of 7-segment LEDs or
equivalent), a button, a battery, and a power switch. It is intended that the box, together
with the sensor, can act as a battery-operated thermometer. The temperature data is then
available on the internet.
d. A cellphone that can receive text messages.
2. Mechanical Requirements of the “third box”
a. This” third box” should be enclosed in some way, and physically robust (can stand being
dropped from the workbench to the floor), and can be turned upside down, with the
circuit, connectors, and switches still working.
b. All cable connections to the third box should have terminating connectors, securely
mounted to the third box. These connectors should be the kind meant to be easily
connected/disconnected by a casual user.
c. When dropped to the floor with cables connected, the connectors or cables should not
break (although it is OK if they become disconnected).
d. If the sensor has been unplugged and is then plugged in, the third box should begin
normal operation without user intervention.
Figure 1: General Physical description of the temperature measurement system.
3. The switch on the third box functions as an on/off switch. When the switch is “off”, the
thermometer system cannot display temperatures and temperature data is not available from
the internet.
4. When the switch on the third box is “on”, the following features are available locally at the
third box. When the button is pressed on the third box, a display on the box shows the
temperature of the thermometer sensor in degrees C. There are no requirements on the
resolution or size of the display. However, it must have the following features:
a. The correct temperature should appear on the display when the button is pressed, with no
noticeable delay. Delays are noticeable if they are longer than about 20 milliseconds.
b. The display should be clearly readable under normal indoor lighting conditions and all
temperatures within the normal range of operation of this device (as specified below)
should be displayed correctly.
c. The button is to be “momentary contact”: When pressed, the display is on, when not
i. Figure: General Physical description of the temperature measurement system.
3. The switch on the third box is intended to be an on/oB switch for the third box. When the
switch is oB, the thermometer system cannot display temperatures and temperature data is not
available from the internet.
4. When the switch on the third box is “on”, the following features are available locally at the third
box.
a. When the bu=on is pressed on the third box, the temperature of the thermometer
sensor in degrees C is displayed as a binary integer on the LED display. (For example, if
the temperature is 11 degrees C, the LED display should be [OFF OFF OFF ON OFF ON
ON]).
b. Temperature Display details:
i. The correct temperature should appear on the LED display very soon when the
bu=on is pressed. (No no ceable delay). (delays are no ceable if they are longer
than about 20 milliseconds)
ii. Nega ve temperatures should appear as a binary number in two’s complement
on the seven bit display.
iii. The bu=on is to be “momentary contact”: When pressed, the display is on, when
not pressed, the display is oB. The display should go dark when the bu=on is
released with no no ceable delay.
ECdi 25°C
File Scale Help About
Remote ON
Internet
connected
Computer
Box with bu=on,
bu=on, switch,
And display:
“third box”
Temp Sensor
2.0 meter Cable,
with 1 or more
connectors
Button Switch
Connector
Phone
connected to
cellular
network
pressed, the display is off. The display should go dark when the button is released with no
noticeable delay.
d. If the temperature sensor is not plugged into the third box, or is not working in some way,
the display should notify the user that there is an error condition.
5. When the power switch on the third box is “on”, the following features are available from
an internet connected computer when appropriate software is run on the computer:
a. The real-time temperature, in degrees C or degrees F, (controlled by the computer user),
is displayed prominently (in a large font) on the computer screen, and updated once a
second.
i. If the temperature sensor is unplugged from the third box, an “unplugged sensor”
message should appear instead of the real time temperature.
ii. if the third box switch is off, a message “no data available” should appear instead
of the real-time temperature.
b. By user action on the computer, the temperature display on the third box can be turned on
or turned off (in other words, the computer can virtually “press the button” on the third
box.) The button response me in this situation shall be less than 1 second.
c. When the computer is connected to the internet, and the switch on the third box is on, a
graph of the past temperature readings from the third box can be displayed on the
computer screen. The graph of the past 300 seconds of data should be available within
10 seconds of the start of the software on the computer.
i. The graph is the temperature in degrees C. The top of the graph corresponds to
50 degrees C, and the bottom, 10 degrees C. The graph should always have these
limits, and is always in degrees C, irrespective of the real-time temperature
display format.
ii. This graph scrolls horizontally, with the latest temperature at the right side of the
screen, and past temperature values on the left side of the screen. Once a second,
a new temperature value is added to the graph on the right side, and the graph
scrolls from right to left . (The look is similar to a “chart recorder”). Older
temperature values scroll off the graph on the left. The chart should have x-axis
labels as described in (iv), below.
iii. The physical size of the graph should be scalable with the mouse.
iv. The total time record displayed on the graph is 300 seconds. The horizontal
graph should correspond to, and be labeled in, “seconds ago from the current
time”. (this means the c marks should be in the range 300->0).
v. If there is data missing (perhaps the switch on the third box was off, or perhaps
the temperature sensor is not plugged in), this should be obvious on the graph
display. Missing data should be clearly discernable from data that is off-scale
(too large or too small).
vi. This also applies to the present time display of data. If the third box is off or the
temperature sensor is not plugged in, the graph should continue to scroll and the
graph data should be shown as missing. When the error is corrected, the graphing
and real time display of data should resume.
6. If the computer is on and the third box is off, the graph and real time display of data should
appear on the computer screen within 10 seconds of the third box being turned on.
Figure 2: Possible look for the computer graph display. New data appears at the right and
the graph scrolls to the left. Here, something went wrong 180 seconds ago, for 20 seconds
or so.
7. When the computer is on and the third box is on, a text message will be sent to a specified
phone number whenever the real-time temperature exceeds a certain value or is lower than
a certain value. The two text messages, the max temperature, the min temperature, and the
phone number can all be altered with the computer user interface.
8. Total Range of Operation
a. The design range of the possible temperature displayed should be at least from minus 10
to +63 degrees Celsius. This does not have to be verified by testing, (simply because it is
not feasible to verify this in this class) but should be addressed by the design.
b. When someone holds the temperature sensor in their hand, the heat from their fingers
should make the temperature go up after a few seconds. Holding a soldering iron close
to or briefly touching the sensor should do the same, even more quickly.
c. In the lab, at room temperature, the output of the thermometer should be approximately
22 degrees C, +-4 degrees C.
d. When placed in a water-ice mixture, the output of the thermometer should be 0 degrees
C, +- 2 degrees C.
graph data should be shown as missing. When the error is corrected, the graphing
and real me display of data should resume.
6. If the computer is on and the third box is oB, the graph and real me display of data should
appear on the computer screen within 10 seconds of the third box being turned on.
i. Figure: Possible look for the computer graph display. New data appears at the
right and the graph scrolls to the left. Here, something went wrong 180 seconds
ago, for twenty seconds or so.
7. When the computer is on and the third box is on, a text message will be sent to a speci&ed
phone number whenever the real me temperature exceeds a certain value or is lower than a
certain value.
a. The two text messages, the max temperature, the min temperature, and the phone
number can all be altered with the computer user interface.
8. Total Range of Opera on
a. The design range of the possible temperature displayed should be at least from minus
10 to +63 degrees Celsius. This does not have to be veri&ed by tes ng, (simply because
it is too me consuming to verify this in this class) but should be addressed by the
design.
9. When someone holds the temperature sensor in their hand, the heat from their &ngers should
make the temperature go up a(er a few seconds. Holding a soldering iron close to or brie?y
touching the sensor should do the same, even more quickly.
10. In the lab, at room temperature, the output of the thermometer should be 22 degrees C, +-4
degrees C.
11. When placed in a water-ice mixture, the output of the thermometer should be 0 degrees C, +- 2
degrees C.
50°
40°
20°
10°
30°
300 200 100 Seconds ago
Temp, °C
115.2°F