Utilizing a Raspberry Pi to make your Home Smarter · 2020. 2. 18. · 3.3 Raspberry Pi & Home...
Transcript of Utilizing a Raspberry Pi to make your Home Smarter · 2020. 2. 18. · 3.3 Raspberry Pi & Home...
Utilizing a Raspberry Pi to make your Home Smarter
Nivetha Karthikeyan
Lily Kwak
Sneha Rampalli
Varun Ravichandran
Anna Song
1. ABSTRACT
Water has decreased in abundance as
communities around the world have faced
severe droughts and shortages. The
devastating effects of these events have led
governments, researchers, and individuals to
make significant efforts to conserve water.
Conservation is hindered by the limitations
of existing infrastructure and traditional
human activities. This makes significant
change difficult to achieve. By utilizing the
potential of home automation, individuals
can find ways to reduce their water usage
without notably altering their daily lives.
The Eco-Shower system invented in
this project achieves just that by reducing
the amount of water coming out of showers
when individuals are engaging in non-
rinsing activities. These tasks include
applying shampoo, cleansing with soap, or
other such activities that do not require the
user to stand underneath the showerhead.
This project traced the creation of Eco-
Shower from the initial design concept
through the building, wiring, coding, and
testing of an alpha prototype. Final
experimental results suggested that Eco-
Shower can reduce the amount of water used
in showers during non-rinsing activities by
approximately 24.6%. The end result was a
device that promotes increased water
conservation by blending home automation
with an environmental focus.
2. INTRODUCTION
In the past few decades,
environmental conservation has become a
front-page issue as scientists and citizens
have strived to conserve Earth’s natural
resources. In particular, water conservation,
even by singular households, can produce
very meaningful results as nearly the entire
population can get involved. One of the
most common and resource-intensive uses
of water around the house is showering,
which accounts for nearly a fifth of an
individual’s daily water usage.1 Recent
innovations in mechanical shower
technology have allowed individuals to save
many gallons of water, helping preserve
existing water supplies. However, more
progress can be made. With countless
improvements in computing and robotics,
home automation offers individuals simpler
alternatives to traditional conservation
methods.
The Eco-Shower combines the idea
of water conservation with the practice of
home automation, creating a system that
simply reduces the amount of water used in
showers. As shown in Figure 1, the system
consists of three main components: a
pressure mat sensor placed under the flow of
water, a solenoid valve unit installed into the
piping of the shower, and a Raspberry Pi /
XBee radio communication set that
wirelessly connects the other two parts.
When a user steps on the pressure mat
sensor, indicating that they are standing
directly under the showerhead, the
communication set sends a signal to the
solenoid valve, the component that controls
the amount of water flowing through the
showerhead. The command prompts the
solenoid valve to remain open and allow the
full volume of water to pass through. When
the user steps off the mat to shampoo or
perform other non-rinsing activities, the set
sends another signal to the valve, telling it to
rapidly open and close in order to decrease
the flow of water.
Figure 1: Eco-Shower Set-Up
3. BACKGROUND
3.1 Water Conservation:
According to environmental
researchers Evett and Kähler, water
conservation is defined as the “management
of water consumption in ways that minimize
waste, maximize efficiency, and help to
maintain adequate supplies of high-quality
water.”2 In 2000, the United States’ daily
use of water per capita was 1,430 billions of
gallons.2 Because the United States has been
using an extensive amount of water,
conservation of this natural resource has
grown increasingly important as states such
as California have faced historic droughts.
In order to combat this issue, California’s
state government passed the Water
Conservation Act of 2009 to dictate water
conservation targets and improve the
efficiency of water distribution for public
and agricultural use.3
Although legislation is being passed
to help preserve existing water supplies,
individuals can significantly reduce the
amount of water used overall. Anyone can
take action, which is often more feasible
than implementing water-supply
infrastructure on a large scale. According to
the Environmental Protection Agency
(EPA), individuals spend 16.6% of their
daily water consumption in showers,
meaning that the average family of four in
the U.S. uses 40 gallons per day showering.4
In total, nearly 1.2 trillion gallons of water
in the U.S. is used solely for showering.4
Reducing the rate of water consumption in
showers from 4.5 to just 2.5 gallons per
minute could save the average family of four
around 20,000 gallons of water per year,
clearly highlighting the potential and
importance of shower water conservation.5
3.2 Home Automation:
Home automation is the ability to
control certain aspects of the house through
the use of sensors and microcomputers. One
example is using a mobile application to
turn on the dishwasher or turn off the
television. Home automation uses sensors to
detect human actions and then inserts those
pieces of data into a “home network.” Once
in the “home network,” programs process
the stream of information to dictate
automatic actions around the household.
Recently, home automation has become a
popular field of study as it directly impacts
and greatly simplifies the average person’s
life. Its main goal is to improve the quality
of life by replacing complex human
interactions with programmable
microcomputers.
Home automation tasks can be
separated into two different types: event-
specific and ongoing. Event-specific
activities only occur at certain times, such as
lights turning on when motion is detected.
These activities, including the shower
automation task completed in this project,
involve binary sensors that are either on or
off based on a user’s action. Meanwhile, on-
going automation takes place in a
continuously detecting environment where
sensors are constantly sending data.
Automatic air conditioning and heating units
are examples of on-going automation
systems where temperature sensors send a
steady collection of data to a central unit. In
order to develop smart home databases and
allow these sensor inputs to be translated
into actions, algorithms must be made to
connect the microcomputers to different
sensors.6 Home automation simplifies
mechanical daily tasks so that they can be
completed by external devices.
3.3 Raspberry Pi & Home Automation
The Raspberry Pi is a microcomputer
that is capable of interacting with the outside
world and undertaking tasks that a regular
computer can accomplish. It has been used
many times in the field of home automation
because of its ability to enhance the quality
of life in houses with sensors. It supports a
large number of input and output
peripherals, devices that are used to put or
get data from a computer. This allows the
Raspberry Pi microcontroller to be a
practical device that is able to communicate
with different sensors. Its features can
therefore be easily utilized to save water in
the household. A significant amount of
water is wasted in the shower as people
often permit the water to run longer than
what is necessary. Pressure sensors used in
conjunction with the microcontroller provide
a viable solution to this pressing problem by
controlling the amount of water released by
the shower. Based off this premise of home
automation, a pressure mat sensor can be
effectively used to detect the individual’s
position in the shower. The pressure mat
sensor was used in conjunction with the
Raspberry Pi microcontroller, since the
microcomputer used the data communicated
to analyze and command the solenoid valve
to open and close.7
4. METHODOLOGY
4.1 Brainstorming
Home automation is a broad and
diverse category that encompasses
everything from controlling air conditioning
to opening garage doors. Therefore, this
project had a significant degree of freedom
with countless possibilities for final
products. The theme of conservation quickly
emerged as a focal point due to its relevance
in daily life, particularly with the rise of the
environmental movement. Automation is
useful in this matter as computer programs
can be utilized to control resource
consumption in households without
requiring external human input.
After a preliminary round of
research, it was discovered that
approximately 1,430 gallons of water are
used in the United States on a daily basis.8
Additional research revealed that showers
are a significant source of household water
usage and personal experience revealed that
water is often wasted when participating in
non-rinsing activities in the shower. This
combination of academic research and
independent experiences culminated to form
the idea for Eco-Shower.
4.2 Materials
4.2.1 Raspberry Pis and XBees:
The central parts of the Eco-Shower
system include two Raspberry Pis in the A+
model and two XBee Modules for wireless
communication. The Raspberry Pi A+
model is a microcontroller that is capable of
transmitting electric voltage, connecting
with USBs, and reading SD cards in addition
to processing and computing. Meanwhile,
XBees are wireless communication modules
that use the ZigBee wireless language
standard to connect with one another. In
addition, a USB to TTL cable, which
contains a USB-compatible end to another
end with four pins that can fit into the
General-Purpose input/output pins (GPIO
pins) of a Raspberry Pi microcontroller.
Therefore, one of these was used to connect
the Raspberry Pi microcontroller to the
computer so that coding could be completed.
The USB Explorer is a device that can
connect the XBees directly with the
Raspberry Pi microcontrollers.
4.2.2 Pressure Sensor Mat:
Cardboard was chosen to construct
the pressure mat sensor due to its cost-
effectiveness and flexibility. The planes of
the pressure mat sensor need to keep from
touching when laid flat, and only bend under
significant human pressure. Additionally,
cardboard is an inductive material; it allows
for the current to flow only when the two
sheets of aluminum foil touch. Otherwise,
the circuit is open with cardboard, and the
material can easily act as a framework to
separate the foil sheets in the absence of
human weight. The aluminum foil was also
readily available and malleable to the rigid
structure of the cardboard. The electrical
tape was used to connect the wires to the
aluminum foil because the tape conducts
current on one side without damaging the
wires. The tape reinforced loose wire
connections as well.
4.2.3 Solenoid Valve Unit:
As shown in Figure 2, the solenoid
valve consists of a metal solenoid head and
plastic valve below. A plastic plunger
normally blocks the inner valve opening and
separates the inlet from the outlet port. The
metal head responds to electromagnetic
fields, in which case it lifts the plunger back
into the head. When current no longer runs
through the solenoid head, the plunger drops
back into place by a coiled spring along the
valve to obstruct fluid flow. Current runs
through the solenoid head when a battery
pack connects to the head’s two metal
extensions via voltage and ground wires.
Both the solenoid valve and the pressure mat
sensor units are encased by waterproof
Ziploc bags.
Figure 2: Solenoid Valve Components9
4.2.4 Circuitry:
Assorted wires were used to connect
circuitry parts and carry current. A wire
cutter stripped the plastic coverings of wires
to expose more metal for circuitry.
Breadboards with indents for wire insertion
were included in the circuitry because they
helped solidify wire connection as a better
alternative than twisting wires together.
Indents on the same rows on breadboards
are also already connected in series by
embedded metal without additional
modification, and help organize circuitry
parts. The pressure mat sensor and the
solenoid valve unit used one breadboard
each.
Numerous 1K Ω resistors were
connected in the circuits as means to reduce
high voltages to prevent circuit blow-up and
short circuiting. In the Eco-Shower, these
resistors were utilized to lower 6V battery
packs to the acceptable 5V for the Raspberry
Pi in both the pressure mat sensor and
solenoid valve unit.
A pack of sixteen standard 1.5V AA
batteries were purchased to power the two
Raspberry Pis and solenoid valve in battery
packs. Battery packs connect all batteries
within their casing in series to produce
higher voltage. Two 6V and one 12V battery
packs were used to power the Raspberry Pis
and valve, respectively. The valve requires
more voltage to power the oscillations of the
plunger than the Raspberry Pi does in
signaling. The 6V battery pack can hold four
1.5V AA batteries, while the 12V can hold
eight. From each 6V battery pack, a red
power wire applies positive voltage to drive
current, and a black ground, uncharged wire
in turn accepts the flowing current. Though
the 12V battery pack in the solenoid valve
unit does not have wire extensions, a clip
collector with the red and black wires was
attached to the positive and ground metal
rings of the battery pack.
Specific to the solenoid valve circuit,
the NPN transistor splits into three prongs
and amplifies the current signal by accepting
the current through the middle prong,
sending the current to high voltage through
the upper prong, and grounding the current
to lower, zero voltage through the lower. A
20V flywheel diode was used in circuit to
direct the current only in one direction, since
the voltage drop across it is as strong as
20V, a large difference. Because the
solenoid valve circuit must be switched on
and off quickly, the diode prevents voltage
spikes in directing the current.
4.2.5 Shower model:
Due to the lack of availability of a
shower on which the solenoid valve could
be installed, a model of a shower was used
for experimental testing. The model was
built with rubber tubing, a funnel, and duct
tape.
4.3 Overview
Figure 3: Eco-Shower Flow Chart
Eco-Shower integrates both home
automation and water conservation. This
automated shower controls the volume of
water released, according to the location of
the individual in the shower. As shown in
Figure 3, when the user exerts pressure on
the shower mat, a solenoid valve installed in
the showerhead is signaled via Raspberry Pi
and XBee communication to increase the
volume of water released. Eco-Shower
consists of three main components: a
pressure mat sensor, Raspberry Pi and XBee
communication, and a solenoid valve unit.
4.4 Experimental Testing:
Difficulties involving the connection
between the Raspberry Pi and the computer
rendered the team unable to make the
Raspberry Pis run the appropriate code.
Subsequently, the wireless prototype could
not be prepared for the initial round of
testing. Therefore, data was collected
through a manual procedure that opened and
closed the solenoid valve to reduce water
flow. First, a length of rubber tubing was
attached to the solenoid valve, which
modeled the way the metal pipes of the
shower would connect to the valve in the
actual Eco-Shower. As shown in Figure 4, a
circuit was created by wiring the solenoid
valve to a battery supply. Water was then
poured into the rubber tubing and the valve
was placed over a labeled collection basin to
gather the volume of water that had been
released. A stopwatch was utilized to
measure the amount of time it took for the
water to fill up to 200 milliliters. This
procedure modeled the water flow rate in a
typical shower. In order to test the positive
impacts of the Eco-Shower, the same
procedure was repeated while opening the
circuit one out of every five seconds, which
drops the plunger and stops the water flow.
Once again, the procedure was timed until
200 milliliters of water had been collected
by the collection basin. The entire procedure
was repeated for a total of five trials, which
increased the data's precision.
Figure 4: Experimental Testing
5. PROJECT DESIGN & RESULTS
5.1 Pressure Mat Sensor
The pressure mat sensor is placed
directly under the showerhead away from
the toiletries to detect user position in the
shower setting. With its Raspberry Pi
connected in circuit, the pressure mat sensor
sends a signal to the Raspberry Pi in the
solenoid valve unit to allow normal water
flow in the presence of significant human
weight. In the absence of great pressure, the
mat signals the solenoid valve unit to reduce
water volume getting to the showerhead,
thus conserving water.
As represented in Figure 5, the
pressure mat sensor, which was constructed
from two pieces of stacked inducting
cardboard coated on the insides with two
sheets of conducting aluminum foil
separated by another cardboard frame. When
the user’s feet are placed on the mat, the two
cardboard planes are compressed until the
sheets of aluminum foil meet. This closes
the circuit and allows electricity to pass
through. The entire pressure sensor in circuit
is encased in an ordinary shower mat that
adds to the convenience of the system.10
The actual pressure sensor acts as an
on/off switch that closes and opens the
circuit. The GPIO pins of the Raspberry Pi,
which are used as generic pins for input and
output, are used to connect the pressure
sensor to the Raspberry Pi itself. In circuit,
the sensor is wired from the top to the 5V
pin on the Raspberry Pi where current is
supplied, and from the bottom to the GPIO
14 pin that detects the opening and closing
of the circuit through the current. This pin
then signals the pressure mat sensor
system’s XBee to communicate with its
solenoid valve XBee and Raspberry Pi
counterparts. The 6V AA battery used to
power the pressure mat sensor system’s
Raspberry Pi is wired through five 1K Ω
resistors connected in series that reduce its
voltage to the 5V that the Raspberry Pi can
accept. Wires, connected before and after
these resistors to pick up the new potential
difference, are then attached to the 5V and
GND pins of the Raspberry Pi to apply the
5V to the board.
Figure 5: Pressure Mat Sensor
5.2 Raspberry Pi/XBee Communication
If the pressure mat sensor is
activated by the user, the system must then
work to reduce the volume of water that is
released by the shower. As soon as the
pressure sensor sends a signal to the
Raspberry Pi, it must communicate with the
solenoid valve, which controls the water
flow. This can be achieved either with
extensive wiring or wirelessly with the
assistance of a second Raspberry Pi and a
pair of XBee modules. Due to the high
volume of water that will be present near the
Eco-Shower, wireless communication is the
optimal method of activating the solenoid
valve. XBees offer a cost-effective and
simple means of wireless communication
between microcontrollers and computers,
typically Arduinos and Raspberry Pis. As a
result, XBees are extremely well-suited to
connect two Raspberry Pis wirelessly over a
short distance.
The Raspberry Pi located within the
pressure sensor mat is connected to the
XBee Series 2 module by a USB Explorer,
which allows the XBee to connect and
communicate directly to the Raspberry Pi
through the Raspberry Pi’s USB port. This
setup is visualized in Figure 6, and the
Raspberry Pi is coded to accept a signal
from the pressure sensor, which causes it to
send an output signal wirelessly via the
XBee. The second Raspberry Pi is also
connected to another XBee module with a
USB Explorer. When the second Raspberry
Pi receives this signal as input, it is triggered
to produce voltage on a GPIO pin to
complete a circuit connecting the Raspberry
Pi, the battery supply, and the solenoid
valve. Please see Appendix 9.2 for code.
Figure 6: Raspberry Pis & XBee Radios
5.3 Solenoid Valve
The solenoid valve is signaled either
to open or close by the pressure mat sensor,
based on the user’s position in the shower.
The valve maintains normal water levels
when significant human pressure is sensed,
and decreases water volume flow otherwise.
The solenoid head is a part of the
circuit, while the valve is easily attachable to
shower systems between the showerhead
and connection. Inside the valve is a plunger
that is normally closed and obstructs water
from flowing out the showerhead. However,
when an electric current runs through the
solenoid valve, the plunger opens and allows
water to flow out normally. Oscillating the
valve plunger by switching the current on
and off results in a decreased water flow
rate.
Figure 7 displays the Raspberry Pi,
relaying pressure mat sensor signals and
changing current, connecting to a 1K Ω
resistor through GPIO Pin 18 to prevent
short-circuiting. The resistor is wired to a
NPN transistor that amplifies the current,
which branches off one way to be grounded
back to the Raspberry Pi to complete the
voltage drop, and another to the 12V
solenoid head of the valve through a 20V
flywheel diode. The valve is powered by a
12V AA battery pack, while the Raspberry
Pi is powered by a 6V AA battery reduced
effectively to 5V by six 1K Ω resistors.
Figure 7: Solenoid Valve Unit
5.4 Data
Five trials were conducted to test
both the control group, which did not use the
Eco-Shower, and the experimental group,
which did use the Eco-Shower. In Figure 8,
the time it took to release 200 mL of water
was recorded in seconds for each trial of
each group. In each trial, the experimental
group required a larger amount of time than
the control group did to release the full 200
mL of water. This was indeed the expected
result as the Eco-Shower system was
designed to release a smaller amount of
water by quickly opening and closing the
solenoid valve.
Comparative Flow Rate Times With and
Without Eco-Shower
Trials
1 2 3 4 5
Time to
fill 200
mL of
water
w/out
Eco-
Shower
(s)
415 407 399 365 448
Time to
fill 200
mL of
water w/
Eco-
Shower
(s)
583 568 468 505 583
Figure 8: Flow Rate Times
5.5 Mathematical Calculations
In order to calculate the individual flow
rates for each trial, the volume of water
collected (200 mL) was divided by that
trial’s recorded time. The percent
differences between flow rates were
calculated to determine the percentage of
water, which can be saved using the
solenoid valve since flow rate and water
volume are interchangeable with a set time
frame. The average of these five percent
differences was taken to find the mean
percent of water users can save while
showering with Eco-Shower when not
directly in the water’s line of flow. See
Appendix 9.1 for calculations.
6. CONCLUSION
6.1 Overview
Eco-Shower is designed to be a
simple addition to household showers that
enables water conservation by automating
the flow of water. Eco-Shower consists of
two primary parts: a pressure mat sensor that
keeps track of a user’s position, and a
solenoid valve that controls the water flow.
The two separate elements are programmed
via Raspberry Pis that communicate
wirelessly through XBee radios. Once the
user places the pressure mat sensor under
the stream of water and screws the solenoid
valve into the piping, Eco-Shower is fully
functional without further effort from the
user, which achieves a fundamental
objective of home automation.
Eco-Shower, as evidenced by the
initial round of testing completed on a
prototype model, is capable of reducing the
amount of water used in a shower during
non-rinsing activities by 24.6%. The
percent difference was used to calculate the
potential flow rate that would result if the
Eco-Shower was installed. Based on the
U.S.’s maximum shower flow rate of 9.50
liters per minute, the calculated flow rate
during non-rinsing activities was 7.16 liters
per minute.11 More than just impacting
showers, though, the technology used to
develop Eco-Shower could also be adapted
for use in washing dishes. Just as Eco-
Shower minimizes water wasted when a user
does not need to be rinsed, a similar kitchen
application could reduce water flow when
dishes are being cleaned and not rinsed. The
overall household effect of Eco-Shower and
similar technologies would be a reduction in
utility bills, a decrease in wastage, and an
advancement in water conservation.
6.2 Challenges Faced
Throughout the process of designing
the Eco-Shower system, several obstacles
delayed progress. Deciding how to detect a
user’s position in the shower involved
brainstorming what sensors could be used.
Multiple sensors were considered, such as
infrared and proximity sensors. However,
infrared would not be possible since it
detects the movement of any object in its
view, so it would mistake the water droplets
coming from the showerhead as the user’s
motions while showering. A proximity
sensor was not the appropriate sensor to use
because the user’s position in the shower is
constantly changing and is different for each
user. Additionally, it was difficult to test the
device on an actual showerhead. A model of
a shower was made by widely available
materials, such as rubber tubing and a
funnel, in order to collect data on how much
water would be saved using this device.
Another challenge confronted was
preventing the water flow from stopping. In
its natural state, the solenoid valve cuts
water flow completely, so it would not be
possible to close the valve partially and keep
a small stream of water flowing. As a result,
the solenoid valve was programmed to
constantly open and close, reducing the
amount of water passing through without
fully stopping the water flow.
The central components of the Eco-
Shower are the Raspberry Pis and the
XBees, but configuring these devices proved
to be a major challenge. While installing the
Raspberry Pis, it became apparent that the
devices could not connect to a television
monitor via HDMI. As a result, the
Raspberry Pis were connected to a laptop
through a USB to TTL cable. By far the
most significant challenge occurred when
the laptops began failing to recognize the
Raspberry Pis when connected. As a result,
uploading the code to the SD cards was not
possible and the wireless prototypes could
not be constructed for testing purposes. A
solution to this problem was achieved by
manually completing the circuit to open and
close the solenoid valve, which successfully
simulated the effect that the final Eco-
Shower would have.
6.3 Future Steps
In its current state, the Eco-Shower
system remains an alpha prototype that
serves as a proof of concept for
automatically creating dynamic water flow
in a shower. Now that initial testing has
successfully been conducted, however, Eco-
Shower is ready to be further developed into
a fully functional and user-friendly product.
Early steps into creating an advanced model
of Eco-Shower would involve replacing the
prototype’s simple, widely available
materials with sturdier, more durable ones.
The cardboard and aluminum foil pressure
sensor mat would be substituted out for a
flexible plastic and metal sheet sensor
encased within a usable shower mat.
Breadboard circuits would also be switched
out in favor of fully encased wiring systems.
The XBee radios are popular in “do
it yourself” home automation projects for
their simplicity. However, it would be more
practical to swap the XBee radios out for a
more modern Bluetooth communication
system, which is commonly used in
commercial products. While all material
replacements would require mechanical
changes, the Bluetooth switch would also
mandate a software update to account for the
difference in technology. The end result
would be a more professional and
marketable version of the original Eco-
Shower system that could be integrated into
real world showers.
7. ACKNOWLEDGEMENTS
The authors would first like to thank
their project mentor, Josh Binder, and
residential teaching assistant, Noah Lee, for
their guidance and support provided for this
project. They would also like to recognize
their mentors from Lockheed Martin
Engineers: Kyle A. Cavorley, Manu
Colacot, Joseph C. Ippolite, and Evan
Kesten. Not only did they provide the
resources necessary to complete the
prototype, but they also aided the process of
constructing the alpha prototype. They
delivered valuable insight to help the authors
understand the key components of the
project, including circuitry and XBees.
Additionally, the authors would like to
express gratitude toward the New Jersey
Governor’s School of Engineering and
Technology, the Director, Dr. Ilene Rosen,
and the Associate Director, Dean Jean
Patrick Antoine, for giving them the
opportunity to do research with helpful
mentors and fellow classmates. The authors
would also like to thank the sponsors of the
Governor’s School of Engineering and
Technology for providing them with the
opportunity to participate in research
projects and develop as future engineers:
Rutgers, the State University of New Jersey;
Rutgers School of Engineering; The State of
New Jersey; Silver Line Windows and
Doors; Lockheed Martin; South Jersey
Industries; Novo Nordisk Pharmaceuticals,
Inc.; and NJ Resources.
8. REFERENCES
1Environmental Protection Agency, Water
Use Today (2015). 2J. B. Evett and K. N. Kähler, Water
Conservation (2015). 3California Department of Water Resources,
The Water Conservation Act of 2009
(2013). 4Environmental Protection Agency,
Showerheads (2015). 5Environmental Protection Agency, Water:
Polluted Runoff (2015). 6I. Fatima, M. Fahim, Y. Lee and S. Lee,
The Journal Of Supercomputing 66,
(2013).
7V. Vujovic and M. Maksimovic, Raspberry
Pi as a Sensor Web Node for Home
Automation (2015). 8J. B. Evett and K. N. Kähler, Water
Conservation (2015). 9IHS Engineering360, Solenoid Valves
Information (2015). 10J. P. Smith, Use a DIY Pressure Plate
Switch to Automate Your Haunted
House (2013). 11Home Water Works, Showers (2015).
9. APPENDIX
9.1 Calculations
Flow rates
1 2 3 4 5
Flow rate without Eco-Shower (mL/s) 0.4819 0.4914 0.5479 0.5013 0.4464
Flow rate with Eco-Shower (mL/s) 0.3431 0.3521 0.4274 0.3960 0.3431
Percent difference 28.8% 28.3% 22.0% 21.0% 23.1%
Average percent difference between flow rates = 24.6%
Calculating flow rate:
f, flow rate (mL/s)
t, time (s)
𝒇 =𝟐𝟎𝟎
𝒕
Example (trial 1):
𝑓 =200 mL
415 s= 0.4819 mL/s
Calculating percent difference:
fwithout, flow rate without Eco-Shower
fwith, flow rate without Eco-Shower
p, percent difference between flow rates
𝒑 =(𝒇𝒘𝒊𝒕𝒉𝒐𝒖𝒕 − 𝒇𝒘𝒊𝒕𝒉)
𝒇𝒘𝒊𝒕𝒉𝒐𝒖𝒕× 𝟏𝟎𝟎
Example (trial 1):
𝑝 =(0.4819−0.4914)
0.4819× 100 = 28.8%
Calculating flow rate with Eco-Shower:
U.S. maximum flow rate = 9.50 L/min
p, percent difference between flow rates
w, the original flow rate
n, new flow rate
𝑛 = 𝑤 × (1 −𝑝
100) = 9.50 × (1 −
24.6
100) = 7.16 𝐿/𝑚𝑖𝑛
9.2 Code for Raspberry Pi