Computer Aided Water Monitoring and Control System J Baumeister ...

Computer Aided Water Monitoring and Control System
1. Introduction
The Computer Aided Water Monitoring and
Control System or CAWMaCS is a shower
control system that addresses the problems
associated with the standard shower systems
currently on the market. The first problem
this project addresses is water conservation.
Currently, Americans use twice as much
shower-water as people in other countries
with comparable standards of living. The
second problem addressed is shower safety.
Each year, there are thousands of injuries
and deaths resulting from shower related
accidents. Team CAWMaCS feels that
these accidents are preventable, and has
taken several steps to solve this problem.
The third and final problem addressed by
this project is sudden temperature
fluctuations in the shower. Temperature
changes occur when an individual is taking a
shower and another person or appliance in
the same household creates a sudden water
surge by flushing the toilet, starting a
washing machine, etc. This draws water
away from the shower and will result in a
sharp increase or decrease in water
temperature, creating an uncomfortable
experience for the individual in the shower.
Addressing these problems will bring many
benefits including conserving environmental
resources, preventing injuries, as well as
J Baumeister, J Edwards
A Mills, K Schutte
University of Nebraska Lincoln
The Peter Kiewit Institute
Omaha, NE 68182 USA
adding an overall convenience to the daily
routine for Americans.
2. Problem Formulation
2.1 Problem Statement
The original need for the project was to keep
shower temperature constant during water
pressure changes created by a toilet flush or
sink being turned on. This concept has
evolved to include water volume
monitoring, wireless communication, and
information storage components. The final
project design addresses two major needs:
water conservation and shower safety.
According to www.alternet.org, less than
1% of the water on Earth is useable
freshwater[1]. Since the amount of available
fresh water is limited, it is important to
conserve as much fresh water as possible so
the plants and animals that depend on it can
continue to thrive. The average American
will save approximately 700 gallons of
water per month by shortening their showers
by one minute[2]. Fluctuating shower
temperatures cause the user to spend time
adjusting the water temperature, therefore
wasting time and water. The CAWMaCS
project eliminates fluctuating water
temperatures, therefore saving time and
water in the shower. The project also
monitors the amount of water being used by
the shower and records this information in a

centralized database which can be easily
accessible by the user. Making the user
aware of the amount of water used in the
shower and providing suggested usage
totals, the user will be encouraged to reduce
their total water usage. Using less water in
the shower results in less water sent to the
local wastewater treatment plant for
processing. The result is less energy
required to filter and recycle the water used
for showering, resulting in the conservation
of both freshwater and energy.
The second goal of project CAWMaCS was
the safety of its users. According to
www.customer.honeywell.com, 30% of
children under the age of 5 are involved in
bathtub or shower-related burn injuries
every year[3]. According to
www.dulley.com, more than 5,000 children
and elderly are scalded each year [4].
Common scalding injuries occur in the
shower when someone slips and grabs the
valve handle for balance, turning the water
to its maximum heat setting. Young
children have thinner skin and are more
susceptible to burns. In addition, the elderly
have reduced sensitivity to temperature and
can unknowingly scald themselves. Table 1
provided by the National Burn Victim
Foundation, illustrates elapsed time and
temperature ranges that will cause 3 rd degree
burns in both children and adults.
2.2 Background and
Research
A number of related projects have been
researched to gather information about
shower systems currently on the market. By
examining these existing solutions, the team
has gained insight into technologies are
available and which designs may work the
best. In many cases the goal was to achieve
a level of functionality similar to these
products while maintaining a lower cost for
the end-user.
Table 1
Time and Temperature Ranges to Cause 3 rd Degree Burns in
Children and Adults
2.2.1 Industrial Liquid Control
System (ILCS)
This system is manufactured by Knight
Equipment[5]. Its primary function is to
automate chemical dispensing, but it also
logs and timestamps daily user activities and
chemical usage data. It includes Windowsbased
software to manipulate the logged
data.
Except the pumping aspects of this system
and its industrial nature, this system is close
to CAWMaCS. Examining this system was
a useful method for exploring means of
valve control, as well as user-interface
design considerations.

2.2.2 Wattson
Wattson is a system manufactured by DIY
Kyoto[6]. The primary function is to make
the user aware of their electricity
consumption.
The system consists of sensors that attach to
a home's fuse box. These sensors are
attached to a transmitter which samples and
sends the data periodically to a base station.
The base station logs and displays the data
on an LCD screen. This base station is a
unique battery-powered embedded device
that can be attached to a PC for more
powerful data analysis. The base station can
run for a year on a set of batteries.
Although it positions itself in a separate
market, it had some impact on our project.
This system points to the advantages of
having a dedicated embedded base station
which was portable, low power, and
unobtrusive. Furthermore the means of
communication may be custom-tailored for
the application.
2.2.3 Low Cost Water Flow
Sensor and Ambient Display
This is a project undertaken by two students
from Carnegie Mellon University. Its
purpose was raise awareness of water
consumption. It consists of a piezo
transducer as a means of determining if
water was flowing in a pipe. A set of LEDs
display different patterns depending on how
long the water was flowing.
Researching this project was important the
unique user-interface element and detecting
flow. It does not provide the amount of data
as the flow sensor used in CAWMaCS, but a
piezo transducer is an inexpensive, means to
gather flow information like a flow
sensor[7].
2.2.4 Control valves
There are two different types of valves on
the market that are designed to maintain
pressure and temperature in a shower[8].
Anti-scald values exist in varying degrees of
complexity. Some simply do not allow the
hot water to be opened past a preset point.
Others attempt to maintain equal pressure in
both valves as a means to respond to
pressure fluctuations. Both of these operate
through mechanical means and cost
anywhere from $15 to $250.
The second product on the market is the
thermostatic valves which are complex and
more expensive, ranging from $400 to
$1000. They offer more control than a
pressure-balance valve and may contain
only mechanical parts or additionally
electronic controls and memory systems.
These are designed to maintain temperature
and pressure. These two valve types are
manufactured by Kohler and Moen.
3 Project Requirements,
Specifications, and Success
Criteria
As a means to measure the success of the
project, 10 success criteria were defined.
The benchmark for a successful project was
determined to be completion of at least 8 out
of the 10 success criteria. Five of the
success criteria were defined by the course
instructor and five of the success criteria
were defined by Team CAWMaCS and
approved by the engineering faculty. The 10
success criteria are listed below:
1. The project team will create a bill of
materials and order/sample all parts
needed for the design.
2. The project team will develop a
complete, accurate, readable schematic
of the design.

3. The project team will complete a layout
and etch a printed circuit board.
4. The project team will populate and
debug the design on a custom printed
circuit board.
5. The project team will package the
finished product and demonstrate its
functionality.
6. The system will conserve 15% of
monthly water usage compared to the
industry standard of 2.5 gallons per
minute.
7. The system will eliminate the possibility
of water temperature surpassing 115°F.
8. The system will be capable of tracking
and logging water for at least 365 days.
9. The system will maintain water
temperature within five degrees
Fahrenheit of the user preset.
10. Evidence of the system’s energy
efficiency will be measurable.
The first success criterion states that Team
CAWMaCS must acquire all parts needed
for the design of their product. This was
necessary for the construction of the product
prototype. Also, a bill of materials has been
maintained for all parts acquired so that an
accurate cost analysis may be provided.
The second success criterion states that
Team CAWMaCS must construct an
accurate and complete schematic of the
system. The schematic design was useful in
a variety of different areas of the project. It
has made circuit construction and
troubleshooting easier, and was also
necessary for the PCB to be created. Orcad
and Eagle software tools were used to
design the schematics for the system.
The third success criterion states that a
printed circuit board (PCB) must be etched
with the circuit created by Team
CAWMaCS. The printer circuit boards were
constructed by Sunstone Circuits with the
grant that Team CAWMaCS applied for.
The forth success criterion states that the
PCB must be populated and debugged.
After the PCB was created by Sunstone,
Team CAWMaCS populated the board and
made minor corrections to fix problems that
were discovered.
The fifth success criterion states that Team
CAWMaCS must package the prototype and
demonstrate its functionality. Team
CAWMaCS demonstrated the finished
prototype on three separate occasions: at E-
Week on the UNL campus on April 23, 2010
in the atrium at PKI on April 30, 2010 and at
the final presentation on May 5, 2010.
The sixth success criterion states that the
shower system will use 15% less water than
the current industry standard shower
systems. This has been accomplished by
notifying the user of the current temperature,
regulating the current temperature, and
recording water usage history. This criterion
ensures the environmental conservation of
the system.
The seventh success criterion states that
water may not reach 115 degrees Fahrenheit
in the shower at any time. The water
temperature is constantly monitored in the
shower system, so that if the temperature
approaches 115 degrees Fahrenheit it will be
reduced accordingly. This criterion helps to
ensure user safety while in the shower.
The eighth success criterion states that the
system must monitor and log water usage
statistics for one year. The daily water
usage statistics are stored at the system base
station. Displaying the user’s water usage
history allows the user to track the progress
of their water conservation efforts.

The ninth success criterion states that the
water temperature in the shower will remain
within five degrees of the user specified
temperature. Keeping the water temperature
virtually constant not only helps to conserve
water, but also makes the shower experience
more enjoyable by eliminating unwanted
fluctuations in temperature.
The tenth success criterion states that Team
CAWMaCS will be able to measure the
energy efficiency of the shower system.
Since one of the objectives of the shower
system is to conserve water and energy, it
would be undesirable for the shower system
to consume more energy than it saves.
4 Production schedule
Throughout the research, design, and
construction phases of the project, Team
CAWMaCS had the advantage of being able
to refer to a number of project planning
documents in order to ensure that the team
was not falling behind schedule. Two of
these helpful documents were the PERT
chart and the One Page Project Manager
(OPPM). The Gantt chart has also been a
helpful project planning tool.
The PERT chart displayed all tasks that
needed completion and identified the critical
path. This helped identify which items
needed the most resources dedicated to their
completion and which items were not of
critical importance.
Another helpful planning tool, especially
during the construction phase of the project,
was the One Page Project Manager. The
OPPM broke down all remaining tasks and
assigned each task a week that it needed be
completed by. The OPPM also identified
primary and secondary responsibility to the
team members for every task that needed
completion. If a task was falling behind
schedule, this helped identify who was
responsible. Team CAWMaCS referred to
the OPPM regularly during the construction
phase of the project to make sure that there
weren’t any areas of the project that were
falling behind schedule.
Team CAWMaCS created a reasonable and
effective schedule and used it to keep
production on track. However, one phase of
the design that fell farthest behind schedule
was the PCB creation. Team CAWMaCS’
original plan was to have the first version of
their PCB made locally. Any mistakes
would be corrected, and the final design
would be sent out to be professionally
manufactured. After the local PCB machine
broke down, Team CAWMaCS managed to
adapt their strategy by ordering PCB boards
from PCB manufactures while staying under
budget. Changes were made to the project
schedule to allow time for unforeseen
technical difficulties that are out of the
teams’ control.
5 Detailed Engineering
Analysis and Design Product
Presentation
5.1 Hardware Design
This section of the document outlines each
subsystem of the CAWMaCS project and
hardware design components contained in
each. A top-down approach is taken for
breaking the entire system down into several
smaller subsystems. These subsystems are
reviewed in more detail below.
5.1.1 Power System
The power source for all subsystems of the
CAWMaCS system comes from the
household 120V AC supply. All integrated
circuits and logic circuits in both the shower
system and base station require either a
regulated 5V DC source or 3.3V DC source.

Linear regulators were used to achieve these
values.
The valve control mechanism had the largest
power consumption of the project. The
Amulet MK-480272C graphical LCD
consumes 1.5 Watts, the Crystalfontz
CFAH2004K-TMI-JP LCD consumes 0.06
Watts, and the XBee modules consume 0.15
Watts each. All other components and
peripherals consume less than 0.06 Watts.
By budgeting in an extra 2.5 Watts of power
for each valve control motor places the total
power consumption for the system at 7
Watts.
5.1.2 Reset System
The circuits in all subsystems have active
low reset signals. For a reset to be triggered,
a low signal needs to be applied for one
minimum pulse length, or 100 µs. To
achieve this, an RC circuit with a 1k resistor
and a 1µF capacitor is implemented, giving
a time constant of 1ms.
5.1.3 Shower System
5.1.3.1 Sensors and Control Network
Subsystem
The water flow meter, temperature sensor,
and valve control mechanism compose the
sensor and control network of the shower
system. The flow sensor is operated by a
reed switch opening and closing a SPST
switch to create a square output wave when
water is flowing. The output from the flow
meter is connected to port F of the
Atmega64A microcontroller.
The temperature sensor subsystem will
consist of a MAX6675 integrated circuit and
thermocouple. The thermocouple is be
inserted into a custom made ½” galvanized
steel coupler. The chip select and output
lines from the MAX6675 are connected to
Port F of the Atmega64A.
The valve control unit consists of two
manual ball valves and two servo motors.
The motors take a 5V DC input and are
controlled by Port F of the Atmega64A.
5.1.3.2 User Interface Subsystem
The user interface subsystem consists of two
dials for user input and an LCD to display
information. The two dials are used to
control water temperature and water
pressure. The dials are connected to rotary
encoders that are tied to Port C of the
Atmega64A.
The LCD for the user interface system is the
CFAH2004K-TMI-JP. The eight data lines
from the LCD are connected to Port A of the
Atmega64A. The LCD draws power from a
regulated 5V DC source. The brightness of
the backlight is adjustable via 10k
potentiometer.
5.1.3.3 Wireless Communication
Subsystem
The main component of the wireless
communication subsystem is the XBee
series 1 wireless module. This module
operates under IEEE 802.15 specifications.
There is an XBee radio as part of both the
shower system and the base station system.
The radios utilize RF communication and
have a range of 400 ft. The radios
communicate with the Atmega64A
microcontrollers via USART. The radios
are connected to Port D of both the shower
system and base station Atmega64A
microcontrollers.
5.1.4 Base Station System
The primary component of the base station
subsystem is the graphical LCD. The
graphical LCD is used to display water
usage information to the user in the form of
a line graph over time. The LCD being used
is the Amulet MK-480272C. The LCD
communicates with the Atmega64A via

USART on Port E. Figure 1 is a high-level
block diagram of the system.
5.2 PCB Design
There was a significant amount of
consideration that went into the PCB design.
There are four boards in total: the base
station board, the shower control board, the
shower switch board, and the shower LCD
board. The shower system was broken into
three boards from the beginning, because
while the actual mounting mechanism was
yet unclear, it was clear that the switches
and LCD would have to be mounted at
differing distances from the surface of the
wall. The controller itself could technically
be anywhere on the rear of the wall. For this
reason they were separated and designed to
be connected via standard IDC pairs. These
boards had no real constraint on size or
shape. By contrast, the base station board
was constrained by the size and shape of the
case we had chosen for it.
While the ICs were mostly surface mount
due to availability constraints, for passive
components, through-hole parts were used
for two reasons. First, we had a large stock
of them and thus wouldn’t have to purchase
any. Second, space and electrical constraints
were minimal and so the additional
challenge of board population and
procurement costs far outweighed any
benefits.
A significant problem faced was providing
adequate isolation between the servos and
the controller. To solve this problem, the
servos were driven at a higher voltage than
the logic so that a linear regulator could
provide isolation. Additionally, the ground
planes were joined at only a small point. A
similar technique was used for the graphical
LCD which requires a higher voltage for its
backlight.
PCB design techniques were employed.
Figure 1
High Level Block Diagram of CAWMaCS Project
Figure 2 Shower Board Populated PCB
Figure 3 Base Station Populated PCB

Traces were laid to take the most direct
route to keep them electrically short, and
busses were kept together for logical
reasons. Traces were also generally laid with
obtuse inner angles to minimize reflection
effects and noise. Related components were
grouped together, and bypass caps were
used on all ICs including the linear regulator
output. On the shower controller, sensor
inputs were placed on the same side of the
board to ease wiring later on. Ground and
power planes were employed on all boards
so that the digital ICs could benefit from the
capacitive effect it provides, as well as a low
impedance outlet to ground to prevent
ground bounce.
The PCB used in the final prototype was
manufactured by Sunstone Circuits and
populated by Team CAWMaCS. The
shower control PCB and base station PCB
are shown below in Figures 2 and 3.
5.3 Software Design
One of the primary functions of the software
design in the shower system is to control the
servo motors that open and close the ball
valves, which restrict hot and cold water
flow. In order to achieve accurate
temperatures required by the project success
criteria, the motors must be able to achieve
very precise and calculated movements.
Also, sensor data received by the
Atmega64A microcontroller must be
received accurately.
Two peripherals provide real time updates to
the system via hardware interrupts. User
input comes from two dials connected to
rotary encoders. Users use the dials to
control water temperature and pressure.
Water flow rate is measured by a paddle
wheel sensor. The paddle wheel sensor uses
a reed switch to generate interrupts on the
microcontroller.
The feedback provided by the thermocouple
and flow sensor is used in a PID system to
regulate the servo positions. This allows
external events, such as a change in water
pressure or user changes via the control
knobs to be accounted for and corrected by
changing the motor position.
There are two pieces of information the
system uses to set valve positions: the ratio
of the valves (hot to cold) and the amount
the valves are open. To simplify, the system
uses a linear approach with the ratio and
total values ranging from zero to one. This
is best described by the Table 2.
Table 2: Linear Approach with Ratio and Total Values
Ranging from Zero to One
From a mathematical standpoint, the method
is simple but powerful. The ratio is
multiplied by the total giving a scale
percentage. This result is scaled by a factor
of two, allowing all possible states to be
reached. As this scaling can result in values
greater than 1, all Hot and Cold values are
limited to a maximum value of 1.
Each servo motor has a set range of motion
measured in microseconds. The range spans
about 1000 microseconds for each motor
and changes to the input value result in a
linearly proportional respond from the
motor. To choose the servo positions, the
hot water servo is directly proportional to
the ratio while the cold water servo is
proportional to 1 – ratio.
While somewhat difficult to design, the true
challenge with a PID controller is in tuning.
There are several tuning methods but most if
not all require heavy testing and a good
understanding of the mathematics of a PID

system. The team invested time in several
tuning methods but was unable to reach an
optimal solution. This is not to say no
solution was found but that better solutions
exist. A flowchart for the PID control
system used in project CAWMaCS is shown
in Figure 4.
The first used method was manual “guess
and check” tuning where the output of the
PID controller was sampled and manually
adjusted until the output stabilized in the
minimum amount of time. This process was
difficult to perform as this is an “on-line”
method meaning CAWMaCS needed to be
running water to generate the needed data.
The team found the tuning process was
somewhat dependent on the input values, the
water temperatures and pressures; response
to changes was not as fast as expected[9].
Figure 4: Flowchart of PID system used in CAWMaCS
The second method, one of the Ziegler
Nichols methods, while seemingly simple in
theory, proved to be very difficult. The
process involves using only proportional
gain, increasing the gain value until the
system oscillates at a fixed frequency[9].
The period of these oscillations and the
proportional gain value are used to find the
proportional, integral and derivative gains
directly. The major difficulty with this
system came from the data generation
process. Getting the system to oscillate at a
fixed rate proved to be nearly impossible.
This may be due to the relatively slow
sample rate (5Hz) used in CAWMaCS.
Without an accurate measurement of the
oscillation period, the PID gains could not
be accurately measured and the system
could not be properly tuned. The team
believes this tuning process could be used
with future revisions of CAWMaCS if
higher speed sensors are used.
Overall the PID controllers used give
acceptable performance for a prototype
system. If CAWMaCS were to be exploited
commercially, more effort will need to be
placed in this area. Future improvements
will likely be settled around the possibility
of changing from servo to DC or stepper
motors and finding a valve that is truly
linear in performance, better matching the
control system.
6 Discussion, Conclusion, and
Recommendations
The original problems being addressed by
Team CAWMaCS was water conservation
and shower safety. Team CAWMaCS felt
that an excessive amount of water was being
wasted in current shower systems. In
addition, the statistical evidence of injuries
and deaths resulting from shower accidents
was significant enough to address. The
shower system designed and detailed in this
report addresses these problems. Five
specific success criteria were defined as a
means by which to measure the success of
the project. The five project specific success
criteria are:

1. The system will conserve 15% of
monthly water usage compared to the
industry standard of 2.5 gallons per
minute.
2. The system will eliminate the possibility
of water temperature surpassing 115°F.
3. The system will be capable of tracking
and logging water for at least 365 days.
4. The system will maintain water
temperature within five degrees
Fahrenheit of the user preset.
5. Evidence of the system’s energy
efficiency will be measurable.
Team CAWMaCS considered several
alternative solutions for the system to
generate the best possible design. The final
design consists of a shower system that
accurately measures water temperature and
flow rate while keeping the water
temperature constant. Current water
temperature is also displayed to the user.
Water usage history is wirelessly transmitted
to the system base station, where usage
history can be viewed up to one year in the
past.
The budget defined for the project was $600.
This amount is significantly lower than the
cost of currently available systems that
perform similar tasks. In addition to the
monetary budget, approximately 1,080 man
hours was the estimated labor cost
distributed among the four team members of
Team CAWMaCS.
Testing conducted on the system has
provided evidence that all of the project
success criteria have been met. Therefore,
the system is capable of conserving water
and creating a safer environment. However,
due to the complex installation procedure, it
is the recommendation of Team CAWMaCS
that the shower system be installed mainly
in buildings being newly constructed or
remodeled. Installing the system into an
existing household would be an
inconvenience and also create additional
costs not accounted for in the budget defined
by Team CAWMaCS.
7 References
[1] T. McCarthy, “10 Amazing Facts About
Worldwide Water Use,” October 2009. [Online].
Available:http://www.alternet.org/water/143275/1
0_amazing_facts_about_worldwidewater_use
[Accessed: Nov 6, 2009].
[2] Virginia Department of Education, “Lessons
from the Bay.” [Online]. Available:
http://www.doe.virginia.gov
/VDOE/LFB/lessonplans/wastingwater/backgroun
d.html. [Accessed: Nov 6, 2009].
[3] Honeywell, “Scalding Statistics.” [Online].
Available: http://customer.honeywell.com/
WaterControl/ Cultures/en-
US/Prevention/Scalding+Statistics/default.htm.
[Accessed:Nov 6, 2009].
[4] J.Dulley, “New shower valves hold water
temperature steady.” [Online]. Available:
http://www.dulley.com/docs/f556.htm.[Accessed:
Nov. 6, 2009].
[5] Knight LLC, “Industrial Liquid Control
System.” [Online]. Available:
http://www.knightequip.com/pdf/b_ilcs.pdf.
[Accessed: Nov 6, 2009].
[6] Diy Kyoto, “Wattson.” [Online]. Available:
http://www.diykyoto.com/uk. [Accessed: Nov 6,
2009].
[7] S. Kuznetsov, “Low Cost Water Flow Sensor
and Ambient Display.” [Online]. Available:
http://www.instructables.com/id/Low_Cost_Water
_Flow_Sensor_and_Ambient_Display [Accessed:
Nov 6, 2009].
[8] Keidel Supply Co., “Thermostatic Shower
Valves,” [Online]. Available:
http://www.keidel.com/design/select/showersvalve.htm.
[Accessed: Nov, 6 2009].
[9] Shaw, John. “PID Algorithm and Tuning
Methods,” Process Control Solutions. [Online].
Available:
http://www.jashaw.com/pid/tutorial/pid6.html.
[Accessed: April 2010]