1. Interim Report 2
Team Pool Systems, Inc.
“We guarantee that each member completed their respective part to the
satisfaction of the group.”
Justin Green
Johnathan Sank
Nicholas Wojtysiak
Thomas Guarino
Sayed Baqar
2. 2
Table of Contents
I. EXECUTIVE SUMMARY ....................................................................................................... 4
II. MARKET ANALYSIS............................................................................................................. 5
GENERAL NEED FOR A PRODUCT ............................................................................................... 5
ESTIMATION OF MARKET............................................................................................................ 6
COMPETITOR BENCHMARKING ................................................................................................... 7
PATENT STUDY............................................................................................................................ 9
COMPETITIVE ADVANTAGE: ..................................................................................................... 14
III. PROBLEM IDENTIFICATION......................................................................................... 14
PROBLEM STATEMENT .............................................................................................................. 14
PHYSICS OF TASK, ARTIFACT OR SYSTEM: ............................................................................... 16
HUMAN FACTORS CONSIDERATIONS: ....................................................................................... 19
IV. HOUSE OF QUALITY ........................................................................................................ 21
CUSTOMER REQUIREMENTS...................................................................................................... 21
ENGINEERING CHARACTERISTICS ............................................................................................. 24
CONSTRAINTS............................................................................................................................ 24
VI. CONCEPTUAL DESIGN PROCESS................................................................................. 27
CONCEPT GENERATION............................................................................................................. 27
Concept #1: Self-Containment Design ................................................................................. 29
Concept #2: Modular Design ............................................................................................... 31
Concept #3: Bottom of Pool Stationary Design.................................................................... 33
Concept #4: Pipeline Attachment Design............................................................................. 35
Concept #5: Side of Pool Attachment Design....................................................................... 37
CONCEPT SELECTION PROCESS................................................................................................. 39
Pugh Chart ........................................................................................................................... 39
ANALYTICAL HIERARCHY PROCESS ......................................................................................... 40
IMPROVED CONCEPT DESIGN.................................................................................................... 51
VII. EMBODIMENT DESIGN PROCESS............................................................................... 52
PRODUCT ARCHITECTURE......................................................................................................... 52
CONFIGURATION DESIGN .......................................................................................................... 54
DFM/DFA/LOGISTICS............................................................................................................... 57
FAILURE MODES & EFFECTS ANALYSIS ................................................................................... 61
MATERIAL SELECTION .............................................................................................................. 64
PARAMETRIC DESIGN................................................................................................................ 66
IX. PROTOTYPING & TESTING............................................................................................ 70
DETERMINING THE TARGET WEIGHT OF THE SYSTEM ............................................................... 70
NIOSH LIFTING EQUATION ...................................................................................................... 72
KEY FUNCTIONALITIES DEMONSTRATED .................................................................................. 75
NECESSARY TRADEOFFS ........................................................................................................... 76
MATERIALS AND PROCESSES FOR PROTOTYPE......................................................................... 78
PROBE ACCURACY TESTING ..................................................................................................... 80
MATERIAL RELEASE TESTING................................................................................................... 82
HUMAN FACTORS CONSIDERATIONS ......................................................................................... 85
MANUFACTURING AND PROCESS COST ANALYSIS .................................................... 86
MANUFACTURING STEPS AND ASSEMBLY ................................................................................ 86
COST ANALYSIS TABLE............................................................................................................. 90
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PRODUCT DESIGN SPECIFICATION (PDS)....................................................................... 91
CONCLUSIONS ON DESIGNED PRODUCT ........................................................................ 93
APPENDIX A .............................................................................................................................. 96
TEAM CONTRIBUTION ............................................................................................................... 96
APPENDIX B............................................................................................................................... 98
WORKS CITED ........................................................................................................................... 98
APPENDIX C ............................................................................................................................ 100
FMEA CHARTS ....................................................................................................................... 100
APPENDIX D ............................................................................................................................ 102
HUMAN FACTORS.................................................................................................................... 102
APPENDIX E............................................................................................................................. 107
MARKET RESEARCH ANALYSIS .............................................................................................. 107
APPENDIX F............................................................................................................................. 108
ENGINEERING DRAWINGS ....................................................................................................... 108
APPENDIX G ............................................................................................................................ 119
ARDUINO CODES ..................................................................................................................... 119
APPENDIX H ............................................................................................................................ 126
HOUSE OF QUALITY ................................................................................................................ 126
4. 4
I. Executive Summary
Automation has always been a sought after process to reduce human effort and
mistakes. However, pool automation for residential owners has been overlooked for
many years. To date, pool owners have a great deal of upkeep when it comes to
maintaining a pool. The process of correctly maintaining chemicals can be tedious and
inconvenient due to the manual procedures that have lingered over the years. For this
reason, Pool Systems Inc. has created the PoolBoi, a self-automated pool chemical
dispenser and tester.
With over ten million residential pools and seven million residential spas located
throughout the United States, Pool Systems Inc. looks to find a home in all of them. In
addition, the U.S market for swimming pool equipment and maintenance products was
valued over $3.4 billion in 2011 with projections to double by 2021 [B 11] . From our
preliminary research, it can be gathered that residential pool owners are interested in the
upcoming innovation known as Poolboi.
The idea of adding chemicals without human interaction is not new. To date, there
are two types of products consumers may buy that will attempt to fulfill this need. The
first are chlorine dispensers that fail to test current chlorine levels and are restricted to
one chemical. The second being integrated controllers that are installed on the pump of
the pool. Due to the complexity of this design and the price tag, this product has a very
limited market and is normally directed towards commercial pools. PoolBoi will be
designed in a way to offer the complexity of integrated controllers while offering the
convenience of chlorine dispensers, all at an affordable price.
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The PoolBoi is designed to be an all-in-one product. The housing will contain the
circuitry, sensors, chemicals, and actuators. Owners will purchase the system as a whole,
fill the chemical reservoirs with their respective chemicals, and place the system into the
pool. The ORP and pH sensors located internally will test the water at certain intervals.
Based on the readings, actuators will open up each reservoir to add the correct amount of
chemicals to properly balance the pool. If reservoir levels become low, the user will be
notified via SMS or email. This makes the system completely self-sufficient with the only
user input being refills.
In order to successfully produce this product at effective margins, detailed thought
has been placed in the manufacturing process. Materials such as PRL-TP-FR-IM-3,
urethane foam, circuitry, and sensors will be purchased wholesale. While suppliers are
needed to make our initial molds, we intend to keep the injection molding process
internally. At the completion of this process, the product will be assembled and ready for
shipment. With our qualified engineering team and third party suppliers, a successful
launch of our product is imminent.
The PoolBoi takes an old procedure and brings it into the 21st
century. We believe
that this product will greatly relieve the stresses faced by pool owners. With this
proposal, we invite you to join our company as we enhance the pool maintenance
industry.
II. Market Analysis
General Need For A Product
As many procedures are becoming automated, several have remained overlooked.
With this in mind, our product is developed to eliminate a time consuming task that many
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pool owners face regularly. The task of testing and adding pool chemicals has become a
hassle. Current pool owners must hand test the water in their pool using special kits.
After these tests are complete, owners must use tables to calculate the amount of
chemicals to add. Since humans aren’t perfect, the precise amount of chemicals is rarely
added. Furthermore, depending on the amount and type of chemicals added, the pool can
become un-swimmable for upwards of a day. It is also worth noting that many of these
owners work fulltime and lack the time to test chemicals daily. Thus, it is clear that a new
product must be designed to solve these issues. While a product needs to be developed, a
market also needs to be willing to purchase and use the product.
Estimation of Market
Using data taken in 2012 from the Association of Pool & Spa Professionals, there are
over ten million residential pools and seven million spas throughout the United States.
This can be seen in the Appendix. While Maryland and the DC area is not listed, it can
give us a rough estimate to how many pools are in each state and the trends for new pool
purchases. It is also worth noting that Maryland is the richest state in the United States
with a median household income of $69,272 according to the 2010 census. Coupling
these stats together confirm that there is a considerable market for our product.
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Competitor Benchmarking
Seeing the potential in this market, companies
have attempted to develop solutions to this problem.
These can be broken down into two categories. The
first category is comprised of floating chemical
dispensers illustrated in Figure 2.1. There is an
abundance of these systems on the market currently.
While these devices add chemicals, they do not check
the current level of chemicals in the water. Therefore, as the device adds chemicals, it is
possible for the levels to exceed the safe and desired range. High levels of chemicals can
create unhealthy swimming conditions and even damage the pool. Short lists of products
that meet this criteria are provided below with observed advantages and disadvantages.
Name of product Price Advantages Disadvantages
Aqua EZ Floating
Pool Chemical
Dispenser $8.98
Holds both 1" and 3" tablets
Allows for adjusting the
chlorine dispensing rate
Floats throughout the pool
Can be placed into pool
without installation
Unable to measure current
chlorine level
Does not add correct
amounts of chlorine
Can get stuck in pool corners
Cheap quality
Only accepts tablets
Swim
Time Floating
Pool Chemical
Dispenser
$48.92
Solar powered
Allows for adjusting the
chlorine dispensing rate
LED indicators for reservoir
levels
Holds both 1” and 3” chlorine
tablets
Floats throughout the pool
Can be placed into the pool
without installation
Only accepts tablets
4 hour runtime on full
charge
Unable to measure chlorine
level
Can get stuck in pool corners
Table 2.1: Existing products with comparisons
Figure 2.1: Floating Chemical Dispenser
8. 8
The second category is comprised
of controllers, which must be
installed to the pump system of the
pool. While these controllers can
test and add chemicals, they are not
integrated into one system. Due to
the complexity of the design,
manufactures must install the
devices. This approach removes
the user friendliness found in the first category. In addition, these controllers are often
priced in the thousands. A short list of products that meet this criteria is provided below
with observed advantages and disadvantages.
Name of Product Price Advantages Disadvantages
IntelliChem Must be
quoted
Programmable
chemical feed cycle
Adds chemicals based
on readings
Expensive
Often requires manufacturer to
install
Not user friendly
Encompasses multiple
subsystems (pumps, valves,
tubing, etc.)
Digital pH/ORP
Wall Mounted
System
$1,834.99
Programmable digital
ORP/pH controller
Control pools up to
100,000 gallons
Comes with all
components required
Encompasses multiple
subsystems (pumps, valves,
tubing, etc.)
Expensive
Table 2.2: Comparison of controller pool stability products
By analyzing the problems found in these two categories, our device will fix these
voids and offer a simplistic device for the common pool owner.
Figure 2.2: ControllerFigure 2.2: Integrated Controller
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Patent Study
By doing some quick searches on the Internet, competitor devices were
discovered. However, a more detailed examination of patents must be done to ensure that
our product is still plausible. Additionally, by using existent patents that perform similar
functions of our design, valuable insights can be discovered and used throughout our
design. In order to find existing patents, our team used Google patent search. This
approach was very straightforward and offered an abundance of options. Similar to
googling, keywords could be entered and a list of patents were displayed. The five
patents our team discovered which may be useful in our design are listed below. A brief
description is listed below each patent.
Patent US 20060131335 A1: A variable water flow and dilution chemical dispenser
Publication Date: June 22, 2006
Inventor: Curtis Hubmann
This patent describes a tool that
can mix liquid chemicals with a stream
of water. The design is rather simple and
encompasses two valves. One valve
(#32) is used to control the rate of
chemicals entering the stream of water.
Likewise, the other valve (#30) controls
the rate of water entering the device.
These valves can be adjusted by rotating
them. This allows for quick and precise
adjustments. However, the device needs
Figure 2.3: US 20060131335 A1
10. 10
to be connected to a pressurized water source to begin diluting the chemicals. This can be
accomplished by using a water hose and connecting it to an adapter (#18). The chemicals
are stored in a container (#16) that sits below the device. When the handle (#17) is
engaged, chemicals flow through a tube (#54) and begin to mix with the stream of water
supplied to the device. The diluted chemicals are then dispensed through a nozzle (#20)
at the end of the device.
Patent US 6309538 B1: Spa Chemistry
Monitoring and Chemical Dispensing
Unit. Publication Date: Oct 30, 2001
This patent is very similar to our
idea in that it is a buoyant product that has
three compartments for respective
chemicals. This system uses sensors to
read the pH levels of the pool and add
chemicals accordingly. The patent
describes a design, which utilizes three
compartments (#54, #55, #56) shown to
the right. Each of these compartments
holds a specific chemical. The design is a free-floating system that requires minimal
human interaction. The sensors work from a controller that tells device to read the levels
in a pool and then take action on whether to release these chemicals or not. The unit is
programmable to operate at certain times during the day.
While this may seem to be identical to our product, our design differs in four
unique ways. First, the design patented above requires the user to purchase new reservoir
Figure 2.4: Patent US 6309538 B1
11. 11
containers when empty. This can become costly and troublesome, as the user will not
know when chemicals run out. In our design, our reservoirs will be able to be opened in
order to visually monitor chemical levels and refill as needed. Furthermore, to improve
the interaction between our device and the user, our product will utilize weight sensors to
measure reservoir levels and provide a SMS or email notification about low levels. Thus,
the user will never have to worry about a chemical container being empty for a large
amount of time which can occur daily for current systems, especially the design
mentioned above. Third, the design above utilizes a metered plunging system in order to
disperse the chemicals from each reservoir into the pool. While this is effective, it also
poses a large problem. If water were to come in contact with the chemicals in the
reservoir, the remaining chemicals could be activated. This would result in the system
being useless until new reservoirs were added. In our design, we are designing a different
actuation approach. Our system will utilize servos and air to add chemicals to the pool.
Upon obtaining a sensor value, the servo will open for a set amount of time. While the
servo is open, chemicals will begin to fall from the reservoir through the air into a small
pocket of water at the bottom of the system. This will ensure that the reserved chemicals
avoid water contact while using gravity as the energy source. Lastly, the design above
floats around by the currents it faces. Since it is designed for a spa, this was most likely
ignored. However for pools, adding chemicals has to be done more carefully. Chemicals
should be added in the deepest portion of the pool and away from walls or light fixtures.
For this reason, our product will be designed in order to stay stationary in the deepest
portion of the pool. With these four features, our product strives to be more innovative
than the patent above.
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Figure 2.6: Patent US 4016079 A
Patent US 4940946 A: Pool water sensor with an extendable prolonged probe for
determining pH and chlorine levels
Publication Date: 1990-Jul-10
This patent is a design for a handheld
probe that uses an ion meter to measure
the chlorine and water acidity levels for
pools. It is battery operated and designed
to be mobile. The device uses two
metallic rods that a DC current runs
through. When inserted into the pool, the
water completes the circuit and the
resistance is used to report the level.
Patent US 4016079 A: Automatic
chlorine and pH control apparatus for
swimming pools
Publication Date: Apr 5, 1977
Inventor: Ernest O. Severin
This apparatus takes two
liquid samples from the pool
into two separate sample cells.
A chlorine reagent is added to
the first sample cell and a pH
reagent is added to the other. A
light is shined through each
sample cell that projects onto
Figure 2.5: Patent US 4940946 A
13. 13
two separate photoelectric cells. The photocells then produce a signal that indicates the
chlorine and pH levels of the samples. Comparators then determine if the levels in the
samples are above or below the prescribed levels, and supply an output signal to flip-
flops, which store the results and send a signal to the drivers. The drivers control the
operation of the chlorinator and acidifier. This operation is repeated periodically on a
timing circuit.
Patent US 4363728 A: Automatic chlorinator for swimming pools
Publication Date: Dec 14, 1982
Inventors: William P. Guglielmi, Richard E. Caserta
This invention is a
reservoir/pump system that you
can attach to the water
recirculation system that is
already part of the pool. The
way this patent works is by
having the pumps release the
chlorine at a steady rate
(chosen by the user so that
different chlorine levels and
compounds can be
accommodated for), and the
reservoir is slowly drained of
the chlorine as it pumps more
out. The idea is that the only Figure 2.7: Patent US 4363728 A
14. 14
user interaction that is necessary for pool maintenance will be keeping the chlorine
reservoir filled with chlorine, keeping the pool chlorinated and clean. The system attaches
to the water recirculation system that’s already integrated into the pool, so that when the
water filters through, small doses of chlorine are added, maintaining the chlorine level at
whatever level the user desires.
Competitive Advantage:
Through the use of market research and patent studies, we have been able to find a
market that can benefit from a product innovation. By analyzing our competitor’s
devices, we can design a product to fix the problems found in each category giving us a
clear competitive advantage. Our product is designed to be as simple as possible without
losing the precision of other controllers. Thus, the user will be able to buy the system as a
whole, alter the settings to their liking, and place the system into their pool. From this
point on, the only task required from the user is refilling the reservoirs when empty. This
approach has the convenience, ease of use, and price tag of floating chemical dispensers
with the precision of integrated controllers.
III. Problem Identification
Problem Statement
Pools require constant maintenance. Any above ground or in ground pool will
require the owner or user to consistently test the chemical balance and add
chemicals accordingly, otherwise the pool will be unsafe to swim in. Once the user does
add the chemicals to the water, the pool will need to be vacated for a period of time to
allow for the chemicals to disperse so that the users don’t come into contact with a
15. 15
concentrated pocket of chemicals. This can also be a potential hazard because if the user
doesn’t follow instructions, they could receive chemical rashes on their body if they go
into the pool too soon after maintenance. Solutions to this will be addressed later. Current
products have the ability to act as a control board that releases chemicals from a separate
reservoir, or can act as a sensor that alerts the user when the levels in the pool are too
low. These devices work well, and give the user total control over the chemical balances
in the pool, but come at a very high cost and are separate units. The user needs to
integrate the control board into a preexisting chemical system. Other products float
around in a buoy-like container or sit in a fixed position and release the chemicals at a
constant rate. These products have several flaws with their design. They’re built to be
convenient and cheap for the user, and because of this, do not fully satisfy the user
requirements. They disperse chemicals at a constant rate that is not chosen by the user,
and because of this they can add too much of a chemical to the pool. Also, they might
add chemicals too close to a pool wall, causing damage to the plastic or light
fixtures. Finally, they only take care of one chemical at a time due to the fact that they
have a single reservoir that is used for chlorine. The product that we are proposing will
tackle these unsolved issues. In the figure below, a fishbone diagram is laid out to list out
the current shortcomings with the different products that are currently marketed to
maintain a pool.
16. 16
Physics of Task, Artifact or System:
The proposal that we’re making will be a device that is incorporated into the pool
that has a control panel with sensors. Surrounding this panel, reservoirs are broken into
three compartments. The device will float in the water, so it will need to be buoyant and
balanced despite potentially differing levels of chemicals in its reservoirs. Another force
that needs to be taken into consideration is the force of the chemicals being released into
the pool. They will be released using the force of gravity, but to open up the chamber to
release the chemicals, a small door will have to open, so the force to open the chamber
and the frictional force of the chemicals against this chamber door will need to be
accounted for. When the user needs to refill the reservoir with chemicals, the force of
gravity on the device will have to be taken into account since the device has to be light
enough so that people of all ages and sizes can easily manage to lift it out of the pool and
place it back in with ease. A free body diagram of the overall product has been provided
to illustrate the buoyancy forces.
Figure 3.1: Free body diagram of entire system
17. 17
Likewise, a free body diagram of the servo and gate has been provided to illustrate the
forces faced while releasing chemicals.
Many issues can arise out of the product (as seen in Figure 3.3) due to human
Figure 3.3: Fishbone diagram
Figure 3.2: Free body diagram of an individual servo
18. 18
error, sensor error, physical error, or issues with the pool itself.
One of the bigger issues with the product will be the imbalance of chemicals in
the reservoirs. Chemicals will be released at differing rates, so the buoyancy force will
have to overcome the moment put on the device by having different levels of
chemicals. Also, if the device is modular in case the user only wants the device to add
one or two chemicals instead of all four, the device will still need to stay balanced.
Some physical considerations need to be made dependent on how the device is
integrated into the pool. If the device is floating in the pool, buoyancy force needs to be
considered. The device must float regardless of the situation, whether people are in the
pool or the reservoirs are completely empty. This device will need to be stable and
buoyant to work, so center of gravity and buoyancy forces are crucial. If the device is
sitting at the bottom or on a wall, a hook may be used to hold it in place so that it doesn't
move or become unattached from the siding/floor. Another consideration is that the
device's density and mass may be enough to fully overcome buoyancy forces so that it
sits flush against the bottom of the pool, however that would require the pool to have a
flat bottom or at least a shape that contours the bottom of the product. In all of these
designs, actuator forces are going to be critical. The device has to have actuators that
allow the chemicals to get released into the pool, so these forces need to overcome
gravity, friction, pressure (if it's at a depth), or buoyancy (depending on what direction
the chemicals are released). Finally, the force it will require to remove from the pool
when the device requires a refill of chemicals, recharge, or physical maintenance needs to
be considered. If the device is too heavy or the center of gravity is off, it may be
troublesome for the user to remove the device from the pool.
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Human Factors Considerations:
The purpose of the design we propose is to limit the human factor as much as
possible to make the pool maintenance more or less autonomous. However, due to the
nature of the task, human interaction with the device is a requirement. One requirement
is that the user will need to occasionally refill the reservoirs where the chemicals will be
contained. Due to the fact that the device will be releasing chemicals into the pool
frequently in small amounts, the user will need to be alerted when the reservoirs are
running low. A program can be written into the product that will allow the user to
receive a text or an email alert so that they know when they need to add chemicals in
again. This will require the user to input their contact information into the device. The
reservoirs will be labeled with which chemicals go where, so adding chemicals to
the device will not be mentally taxing at all. The user will simply have to remove the
device from the pool, open the reservoirs up, add the chemicals in, and then place the
device back into the pool.
Another human interaction with the product will be entering the size of the pool
so the device knows how much of each chemical to add. In order to do this, the user will
need to know the size of the pool, which shouldn’t be an issue if they’re in charge of
maintenance anyway. The device will simply need to know the amount of water in
gallons so it will add the proper amount of chemicals. Also, if the user doesn’t want to
fill all of the reservoirs with their respective chemicals, then they will simply need to
leave them empty.
Previously, when the users added chemicals to the pool, a brief period of time
would need to be avoided so that chemicals could disperse in order to avoid topical
20. 20
irritations. With the product that is being designed, the chemical level released will not
be harmful to humans. However, in order to ensure that the chemicals added are
dispersed safely, a blinking red light will signal users that chemicals have been added to
the pool. After a period of thirty minutes has passed, the red light will turn off signaling
users that the pool is safe to swim in. This is one less interaction that the user will have to
worry about.
In order to input all of the required information for the product to work, the user
will have to interact with an LCD screen that will be attached to the device. There will be
a button controller system next to the LCD screen for the user to input all of the required
data into. The device will have code entered into the motherboard so that the user will
only have to input the numbers, and the product will perform all of the necessary
calculations to determine how much chemical needs to be added given the environment it
detects. As stated above, this same code is responsible for sending the user an SMS
message or an email to alert them about low chemical levels. In order for this to be
possible, the LCD screen will prompt the user to enter an email and/or a phone number to
text.
One major factor that will have to be taken into consideration is the weight of the
device. If it is too heavy, an older person or someone who is physically disabled may
have a harder time retrieving it from the water, so it needs to be lightweight enough for
anyone to be able to remove it from the pool. The initial goal for the design is to have the
product weigh less than 15 pounds so that it will not be hard for anyone to pick it
up. However, after conducting an anthropometric analysis (which will be touched upon
in detail later in the paper), it is determined that the goal weight to satisfy a slight
21. 21
majority of the population, while also taking reservoir size and chemical amounts into
size, is 40 pounds. Also, the retrieval itself will have to be taken into consideration. If the
device is floating closer to the center of the pool (so that chemicals don’t get released too
close to any walls), a rod with a hook at the end or a skimmer may be used to pull the
device close to the edge so the user can retrieve it. This may be an issue if the user uses
the product without having a retrieval device, possibly requiring them to jump into the
pool and getting it themselves. After conducting the anthropometric analysis, it is
determined that the user’s knees will be the point of failure before any other body part if
the device is retrieved from a bent over squatting position.
Finally, the user will need to recharge or replace the battery every so often in the
device. A text or an email alert will be sent to the user when the battery level becomes
too low so that they have plenty of time to replace it. If the device is used in an outdoor
pool, a photovoltaic cell can be placed on top to automatically charge the
battery. Otherwise, the device will have to have a replaceable battery. Since the device
will be in standby mode for the most part (other than when it’s testing the levels and
releasing chemicals), the battery life should be very long so that replacement shouldn’t be
too often.
IV. House of Quality
Customer Requirements
Lightweight
Large chemical reservoir
Long battery life
22. 22
Ability to test pool often or continuously
Minimize pool maintenance
Smaller in size
Test chemical levels accurately
Lower in price
Durable
Chemicals contained safely
The customers that we are targeting the automated pool chemical dispenser
towards have a long list of specific requirements. In order to be a legitimate company
with a competitive product, we must first identify who our customer is and what
requirements they are seeking in our product. We then need to rank and prioritize that list
of requirements in order of ranking of importance to the customer's needs and wants. The
first requirement is the product must be lightweight; the product is required by the
customer to be light and mobile. In order for the device to be pulled out of the pool and
maintained, it must be relatively lightweight in order to maximize the convenience to the
user. The device must be able to be picked up and carried by children and older people. A
large chemical reservoir is needed to minimize the maintenance of the device. The large
chemical reservoir must hold enough chemical materials for multiple disbursements. This
ensures the device is easily maintained for the user. The lightweight and large reservoir
requirements are clear tradeoffs. As the reservoirs are increased in size, the weight and
size of the device goes up. A long battery life is also needed to minimize the
maintenance. The battery life ensures the device will be working properly and the pool
23. 23
will be at optimum chemical levels. The battery size is another tradeoff with weight. As
the battery increases in size, the longer the device will last; however the weight will
increase. Another requirement is the ability to test the pool often or continuously. This
ensures the pool’s chemical levels are at safe and sustainable levels. The device has to
test the pool’s pH, chlorine, and bromine levels at short enough intervals to properly
disburse the correct amount of chemical materials. Next, the customer requirement of
minimizing pool maintenance is very important. It means that the device simplifies the
pool maintenance process by eliminating complicated steps. Smaller in size is another
requirement by the customer. This means that the device is dimensionally small enough
to be able to be moved to and from the pool with ease. The device can be removed from
the pool at any time, therefore it must be small enough to be picked up and moved
without being a major burden to the user. The system must be compact enough to be
carried by almost anyone, from children to the elderly, each customer has to be able to
pick it up and move it. Another requirement is to test chemical levels accurately, this is
required to ensure the device works properly. In order to maintain the pool at the proper
chemical levels, the device must be accurate with its readings. The customer demands
that the system add the proper material and in order to do this, the system has to be able
to read the correct chemical levels. A reasonable price is required by the customer to
ensure the worth of the device. It must be low enough to be affordable so the customer
can purchase it. Durability is required to make the device long lasting for year after year
use. The device is mobile therefore it must be tough enough to be dropped at a reasonable
height and not break. The last customer requirement is that the chemicals have to be
contained safely. The chemicals, specifically chlorine, are dangerous chemicals. Thus,
24. 24
the device has to store them safely and not expose them to people or animals. It is
required to contain the chemicals in order to disburse them at the proper times and limits.
If the device cannot hold the chemicals securely, the pool will be not be balanced and the
customer will not be content with the device.
Engineering Characteristics
Testing frequency (hours)
Power efficiency (η = %)
Chemical capacity (Liters)
Device weight (kg)
Stability (degrees)
Material toughness (KJ/m^3)
Battery life (days)
External dimensions (m^3)
Water resistance (m)
Actuator power output (Joules)
Constraints
Cost
Size
Weight & Stability in water (buoyant or not)
Portable power capacity
Establishing the engineering constrains is vital in the product development. The
engineers must identify and decipher the customer requirements. Those requirements
have to be converted to a quantitative factor that the engineers can interpret and design
for. Constraints are inevitable in designing a product. There are some constraints in the
design of our product. The first constraint is cost. We must design and manufacture a
product that will cost $750. Market research has shown that comparable systems are all in
25. 25
this range. In the current market there are a cheap alternatives which come with a price
tag of $60. However these are not fully automated and have a considerable amount of
user input. Likewise, there is also a more expensive alternative encompassing complex
integrated control systems. These control units cost over $1800. With this information
along with our manufacturing cost, we chose a cost of $750 to be a very competitive and
fair price for the customer. Additional information about the market and the
manufacturing costs can be found in their respective sections. With still having a
complicated system such as ours, designing and manufacturing a product for that price
will be difficult. The group will have to be smart with the materials and use quality parts
that are low priced. Our device requires very specialized equipment such as the sensors,
microcontroller, and actuators. These specialized parts are hard to manufacture and are
expensive. Most of this equipment will have to be outsourced to allow for cheap
purchasing. We initially will not be producing enough products to be able to internally
manufacture each specialized part. This manufacturing constraint ensures our product
satisfies the customer requirement of reducing cost. Another constraint is the size. The
size must be small enough to be carried in and out of the pool by the user.
Also, it is designed to be on the pool surface; therefore the device cannot be too
big to interfere with the users of the pool. It cannot be such a burden to the pool users that
the device would have to be taken out of the pool while the pool was being used. Another
constraint is weight; when the device is fully loaded with chemical materials, the devise
has to be able to be carried by a person and placed onto the pool surface. A second factor
that is connected to weight is the device must float on top of the water in a stable fashion.
An additional constraint is portable power capacity. The device is to be powered by
26. 26
portable batteries for a minimum length of time. This ensures the system can be easily
maintained. The batteries and the chemical material are fairly heavy therefore the amount
of each is constrained.
For the most part, the House of Quality’s relationship between the Customer
Requirements and the Engineering Characteristics is fairly suitable. The results that we
will discuss can also be seen in Appendix F.
Outside the actuator power output Engineering Characteristic, all of the
weight/importance scores were relatively high. The highest was device weight and the
second place was chemical capacity. Those two ECs were much higher than the majority
of the remaining ECs, having a score of over 400. The majority of the weights were
around 200 to 300. External Dimensions were also up close to 400. This tells our team
that the size and weight of the device are extremely vital to a successful design.
Therefore, we will have to be extremely careful to optimize the size and weight of the
device. We will have to prioritize the weight and size over other factors such as power
efficiency. This is very useful information in creating the most successful product that we
can. The lowest is actuator power output with stability coming in second and power
efficiency, third. This tells the group that the power does not have a great deal of
importance to the overall design of this project.
“We guarantee that each member completed their respective part to the satisfaction of the
group.”
Justin Green
Johnathan Sank
Nicholas Wojtysiak
Thomas Guarino
Sayed Baqar
27. 27
VI. Conceptual Design Process
Concept Generation
When attempting to fulfill the wants and needs of an automatic chemical
dispenser, we had to factor in the functions that make this device possible. The function
structure below in Figure 6.1 illustrates a mapped out diagram to describe the functions
required and the process of functions that this device needs to accomplish. The user starts
by adding the respective chemicals into the reservoirs, then the device needs to be able to
hold those chemicals. The system is required to turn on and test the level of chemicals in
each reservoir and then test the pool chemical levels. If the pool needs more chemicals, it
will then disperse the appropriate amount of chemicals needed and retest the pool levels
to make sure that the concentration is appropriate.
The five concepts that we selected will be discussed further in the figures below.
Each concept has its advantages and disadvantages that make it a feasible option for this
product idea. The concepts will be able to fulfill the functions that we require in order to
make this device operate fully and smoothly. Concept #1 resembles the patent US
6309538 the most due to its main functionality and design. However, what differs from
that patent and our concept is that the materials are prepackaged, the design is made for a
spa, there is no reminder for when chemicals get low, there is no component to keep the
device in deep ends of the pool, and the actuation system uses a plunging measurement
device. Whereas in our first concept, the actuation is based on a servo gate-opening
system that enables appropriate dispersing of materials.
30. 30
This device, in Figure 6.2 above, will consist of two main assemblies: the
containment system and the shell. The containment system will encompass the
handle (1), containers (2), lids (3), intermediate channels (4), actuators (10&11), and
weight sensors (12). This entire assembly will be removable from the shell and can only
be inserted one way. Users may pick up the entire system with the reservoir handle (1).
However, once removed from the pool, the handle can be twisted to unlock the reservoir
from the shell (5). Each chemical is added to its assigned reservoir by opening the lid (3)
and pouring in the chemical. Once complete, the containment assembly is reinserted into
the shell (5) and placed into the pool or spa. When the designated time occurs, the system
users the sensors (9) located at the bottom of the shell to test the pool chemicals. Based
on these chemical readings and our coding scheme, the gate between the container and
intermediate channel (10) will open and release the stored chemicals. Once the correct
amount is released, the gate will close. At this time, the second gate (8) will open and
release the chemicals into the pool. This approach will ensure no pool water can
contaminate or activate the chemicals in the reservoirs. A sensor located at the bottom of
each container will continuously measure the level of each chemical. This will be
displayed on the LCD display (7). It is also worth noting that the LCD display (7) and
number pad (8) will be used to display and alter critical device settings.
Using the design above, much strength can be observed. First and foremost, the
system is a modular design. By being able to remove the reservoir system, filling each
container becomes effortless. Furthermore, the configuration of the containers utilizes
gravity as an energy source for adding chemicals into the intermediate chambers. This
saves valuable energy and can increase the time the sensors can test the pool. However,
31. 31
this configuration also presents one of the biggest weaknesses of this design. As some
chemicals are added more frequently than others, each reservoir level will be different.
This unbalance of weight will provide difficulties in stabilizing and balancing the device
in water.
Concept #2: Modular Design
Parts:
1. Central Control Unit
2. Connection Interface
3. Modules
4. Sensor Unit
5. Deployment Unit
6. Chemical Reservoir
This concept in Figure 6.3 above will address the issues associated with
maintaining a pools chemical levels. This system will automatically detect chemical
Figure 6.3: Concept 2, Modular
32. 32
levels in the pool and adjust them accordingly by injecting the chemicals automatically.
This concept functions on a modular architecture, where there is a central controlling
unit, which is connected to various modules. Each module is specialized for a different
pool chemical, which is stored inside of it, along with a deployment unit and a sensor unit
specific to that particular chemical. This modular architecture will grant users greater
customization to meet their pool’s maintenance needs.
Each system will need to have a central controlling unit (1), which will be
connected to one of the modules (3). No matter how many modules are needed in the
system, only one controlling unit is required. The controlling unit (1) will have a LCD
display, LED indicator lights, and arrow and selection buttons which will allow the user
to set the functionality of the system. The module (3) will be able to float horizontally on
the pool with the water level indicated in the figure. The module (3) will also house all
the components of the sensor, deployment unit, and the chemical. The chemical reservoir
access (6) is located on the top of the module (3), which the user will use to refill when
reservoir levels are low. The sensor unit (4) protrudes out from the module’s (3) lower
portion and will remain under water while the system is deployed. The sensor unit (4)
will be able to sample and test the pool’s water for the chemical that certain module is
designed for, and relay this information to the controller (1). The controller (1) will then
determine if the level of the chemical in the pool need to be adjusted. If necessary the
deployment unit (5) will be actuated to deploy the chemical into the pool. The modules
(3) will be connected to each other through a common connecting interface (2). This
interface mechanically connects the modules (3) to each other; but more importantly
stables each modules connection to the controlling unit (1). The side drawing in figure 1
33. 33
depicts the female interface of the connector (2), while the other side will have the male
interface.
Concept #3: Bottom of Pool Stationary Design
Figure 6.4: Concept 3, Bottom of Pool and Stationary
34. 34
Parts:
1. Chemical Chamber
2. Battery Pack
3. Actuator System
4. Smaller Chemical Chamber
This device in Figure 6.4 above will sit flush against the bottom of the pool in the
deep end so that there will be no accidental bumping or touching the product. In the
figure, the #1 displays the chamber that the chemicals will be contained in. At the top are
four holes where the chemicals can be pushed through. The #2 shows the battery pack,
which will sit at the bottom of the device. In this design, it will use a battery that will last
long enough for the entire time the pool is filled with water, requiring no change until the
season is over. In the mini diagram, it shows the method for pumping the chemicals into
the water. The #3 is an actuator system that will load itself with chemicals from the force
of gravity, and then push the chemicals up into the smaller chamber #4. Once the plunger
from #3 is inside the chamber 4, the holes will open up at the top and the plunger will
push the chemicals all the way into the pool. Once the face of the plunger is pressed
against the holes, the holes will close and the plunger will retract, ensuring that no water
gets inside the device. More chemicals will fall into the plunger and the cycle will repeat
every six hours or so.
The advantage to having the device sit at the bottom of the pool and release
chemicals from its top is that the chemicals will not come near any walls, ensuring that
corrosion of the pool walls will be minimized. Also, it will be out of the user’s way when
swimming, having an advantage over floating pool devices. This is also an aesthetic
advantage so that you can’t really see the device around the pool. Finally, the battery and
35. 35
chambers will be large enough so that you will only have to refill/recharge them once per
season so that the user never has to worry about the chemical levels during the summer.
Concept #4: Pipeline Attachment Design
Parts:
1. LCD Screen
2. Chemical Reservoirs
3. Inlet Pipe
4. Outlet Pipe
5. Power Center
6. Sensors
7. Power Input
Figure 6.5: Concept 4, Pipeline Attachment
36. 36
This concept design in Figure 6.5 above solved the issue of constant maintenance
of pool chemical balances. The system sits after the filter and heater system if installed.
Unlike the other concepts that are proposed, this design sits outside the pool, within the
pool plumbing system.
The design is a polymer box with dimension of 36 inches wide by 24 inches wide
by 24 inches tall. It utilizes a LCD screen for the user to input information about the
specifics of the pool and desired chemical levels. The screen also read outs real time and
past data on the chemical levels to inform the user of the pool’s changing properties, as
well as reading out chemical material levels within the device and warn the user if a
problem is occurring. The heart of the device is the power center. The power center
controls the LCD screen and chemical material addition. The center reads the sensor
input and calculates the amount of how much chemical material must be added. It also
powers the actuators and draws the power from an outside power source such as the
house or pool system. This design features 3 chemical reservoirs; chlorine, bromine, and
pH reducer. The reservoirs are designed such that to hold enough material to last a typical
summer season without refill. Piping runs through the system where the three sensors;
chlorine, bromine, and pH reducer are installed to. The actuators are also installed onto
this pipeline to add the chemical materials as needed.
37. 37
Concept #5: Side of Pool Attachment Design
Parts:
1. Locking Hinges
2. Handle
3. Interface LCD Screen
4. Interface Keyboard
5. Chemical Sensors
6. Upper Chamber Reservoir
7. Chemical Tube Slots
8. Upper Chamber Actuator
9. Lower Chamber Reservoir
10. Lower Chamber Actuator
11. Flow Gates
12. Flow Gate Elbow Joint
13. Battery Compartment
Figure 6.6: Concept 5, Side of Pool
38. 38
This design concept in Figure 6.6 is a box-shaped chemical dispenser that is intended
to sit on the edge of a pool and stay locked in place with locking hinges [1]. There are
handles [2] on each side to allow for portability to be placed anywhere around a pool.
The device is to be programmed by the interface screen [3] and keyboard [4]. Three
chemical sensors [5] are suspended into the water to take readings based on the
programmed intervals. If the pool needs to disperse chemicals, the system will turn on
and initiate the upper chamber reservoirs [6]. There are three chemical chambers that fit
into the chemical tube slots [7] on the top of the device. The upper chamber actuator [8]
then disperses the appropriate amount of chemicals into the lower chamber reservoir [9].
The lower chamber actuator [10] is then activated and disperses the chemicals through
flow gates [11], which flows into the pool by gravity. The flow gates are connected to the
lower chamber reservoir by a flow gate elbow joint [12]. The device is battery powered
with its battery compartment [13] being on the side.
This device has its advantages because it is very easily incorporated to the pool and
the user has its leisure to place it wherever they please. Also, this device is not attached to
a pump system or free floating in the water so its more accessible. However, having
sensors suspended right into the water could possibly be dangerous if their insulation
becomes damaged. This device also shoots its chemicals close to the wall/pool lining
which could be harming and costly to repair if the pool gets damaged.
39. 39
Concept Selection Process
Pugh Chart
The five generated concepts that were previously discussed were then subjected
into a Pugh Chart in Chart 6.1 above to compare how each design related to the datum.
The datum we chose was Concept 1, the free-floating chemical dispenser, due to its
simplistic multifunctional design. The remaining four concepts were then compared to
that datum to determine its functions, strengths, and weaknesses with respect to Concept
1. Each engineering characteristic we chose based on the House of Quality above was
given a “+”, “-“ or “S” for each concept design based on how well it compares to the
datum. The “+” indicates that the concept was deemed better at meeting the selection
criteria, whereas the “-“ indicates the inverse relationship. A rating of “S” means that
both the concept and the datum are even on that selection criterion.
Following the Pugh analysis, we were able to eliminate two concepts based on
how they performed versus the datum. Concept 3, the heavy bottom of the pool design,
Concepts
Selection Criteria Concept 1 2 3 4 5
Device Weight S - - -
External Dimensions D S - - -
Stability A + + + +
Material Toughness T S + - +
Chemical Capacity U S + + S
Power Output M S - - -
Battery Life S + + -
Actuator Power Output S - - S
# of Pluses 1 4 3 2
# of Minuses 0 4 5 4
Chart 6.1: Pugh Chart Comparison
40. 40
and Concept 4, the pipe integrated design, could be eliminated. They both possessed a lot
of positive attributes, however the negative attributes outweighed them. Concept 3 was
eliminated because of its bulkiness and expensive technology needed to manufacture.
Concept 4 was eliminated because of the abundance of pipeline pool chemical dispensers
available and the power output needed. Therefore, we found that Concept 1, Concept 2,
and Concept 5 will be further considered to create the best automatic chemical dispenser.
Analytical Hierarchy Process
Using the Analytical Hierarchy Process (AHP), we were able to further test each
design criteria with each design concept to assist with which concept is most feasible. To
begin a complete AHP process, we had to create a table rating each criterion against one
another, which can be seen below in Table Figure 6.7. After making all the ratings we
then summed up each column to give us a total value for each design criteria.
After we made those assumptions, we then normalized each value in the weight
table by taking the given value and dividing by its summed value for the respective
column. From there, we could take the average of the entire row for each design criterion
to give us a weighted value, {W}. This weighted value describes which criteria we
Figure 6.7: AHP
41. 41
believe is most important to our final design. As can be seen in Figure 6.7 below, the
chemical capacity and the device stability is the most important aspects that should be
considered for our final design.
The last part of the AHP process that needed to be completed is the consistency
check to make sure that our assumptions earlier from the design criteria are justifiable. In
order to ensure these values, we had to create a weighted sum vector, {Ws}, which is a
matrix multiplier between a design criteria row of values and the weighted sum values
that were previously shown in Figure 6.8 above. From there we had to create a
consistency vector, {Cons}, by dividing the criteria weights from the weighted sum
vector. After all of those calculations, we then could take average value for the
consistency vector column, λ, to get achieve a consistency index, CI. Finally, we can
check to see if our assumptions are consistent by finding the consistency ratio, CR. This
ratio is equal to the consistency ratio divided by the random index (RI), which is equal to
1.24 based on the number of criterion we are testing. As can be seen in Figure 6.9 below,
the calculated CR value is less than 0.10. This measures that our provided assumptions in
the first part of the AHP process are justifiable.
Figure 6.8
42. 42
Figure 6.9
After performing the complete AHP process on the design criteria’s and
concluding that our assumptions are consistent, we then can take our concepts and rate
them against one another in AHP to narrow our options down to just one concept. To
begin this process, we have to rate each of the three concepts against each other for each
criteria, then normalize the values we received to find the design alternative priority
values, and last apply a consistency ratio to ensure that our values are correct.
First, we applied AHP to test the concepts for the device weight criteria. From
normalizing our ratings, we found that Concept 1 rated the best in out of the three in
terms of weight meaning that is the lightest out of the three. To make sure that this was
consistent, we performed a consistency check and the ratio was less than 0.10, therefore,
our assumptions are okay. The ratings can be seen below in Figure 6.10 through Figure
6.12.
43. 43
Figure 6.10
Figure 6.11
Figure 6.12
Second, we tested the concepts for the external dimensions criteria. According to
our assumptions, Concept 1 is the most feasible in terms of the external dimensions. This
means that this concept will conserve more space than the other concepts. The weighted
values are consistent to validate our choices. These values can be seen from Figure 6.13
through Figure 6.15.
44. 44
Figure 6.13
Figure 6.14
Figure 6.15
Third, the stability criteria were tested amongst the three concepts. From Figure
6.16 – Figure 6.18 below, we were able to see that the stability was best for Concept 5.
This makes sense because of the product being stationary and not being subjected to any
flotation like the other two concepts. The consistency ratio is less than 0.10 so our
assumptions are justifiable.
45. 45
Figure 6.16
Figure 6.17
Figure 6.18
Fourth, we compared the concepts against one another for the material toughness
criteria. Figure 6.19 through Figure 6.21 shows that the material toughness is best for
Concept 2, followed by Concept 1 and then Concept 5. The material toughness is greater
for the first two because they will be subjected to water along with weather and normal
wear and tear. The consistency ratio backs these values.
46. 46
Figure 6.19
Figure 6.20
Figure 6.21
Fifth, we tested the chemical capacity against all the three remaining concepts.
From Figure 6.22 through Figure 6.24, Concept 1 and Concept 2 are fairly even when it
comes to the chemical capacity. However, Concept 5 has the highest rated capacity
because this product does not need to worry about weight as much due to its stationary
position outside of the pool. Therefore, Concept 5 can afford to carry more chemicals
47. 47
than the other two concepts since we neglected buoyancy for that design. The consistency
ratio supports our assumptions.
Figure 6.22
Figure 6.23
Figure 6.24
Sixth, the battery life for each concept was tested. The values we gave each
concept and that we received from Figure 6.25 through Figure 6.27 show that Concept 5
is favored for battery life. As previously stated in the chemical capacity table analysis,
48. 48
Concept 5 can be heavier than the other two. Therefore, a heavier battery can be used to
allow for longer battery life. These values are consistent due to the ratio.
Figure 6.25
Figure 6.26
Figure 6.27
Finally, we can create a final rating matrix in Figure 6.28 and find an alternative
value for each concept to see which concept is rated the highest. As can be seen in Figure
49. 49
6.29 below, Concept 5 has the highest rated value, followed by Concept 1 and then
Concept 2.
From this AHP process and further group discussions, we eliminated Concept 2
from consideration mainly because of its unsymmetrical design and alternative value
score. With Concept 1 and Concept 5 still in contemplation, we had to consider the
design, production, and function factors for each concept. We concluded by eliminating
Concept 5 even though its alternative value was much higher than Concept 1’s. The
reasoning behind eliminating this concept was because of its more in depth design, its
need for stronger and most likely more expensive materials needed to produce, and the
inconvenience of being stationary on the side of pool.
However, we still were not completely sold on our idea for the original design
draw up for Concept 1. We decided to use the same shape that can be seen in Concept 1,
but change up some of the placements of the parts to make the concept be less cluttered
and more visually appearance. The new design draw up can be seen in the next section.
Figure 6.28
Figure 6.29
51. 51
Improved Concept Design
Figure 6.30: Improved concept design
Parts:
1. Handle
2. Housing
3. Foam Base
4. Lid Attachment
5. LCD Display and Keypad
6. Chemical Reservoirs
7. Electronic Components
8. Chemical Divider
9. Probe Tunnel
10. Servo
11. Gates
52. 52
In this new concept design, the device will have the same exact functionality as
was stated earlier for Concept 1. The sole purpose of this new sketch was to better place
our parts in order to make this product look more appealing and also function smoother.
This concept will function by being placed into the deep end of the pool using the
handle (1). All of the components will be inside the housing (2) and will be floating in the
water. The foam base (3) will assist with reducing weight while also allowing for better
buoyancy. The lid attachment (4) has the handle on it and will be latched onto the
housing to eliminate water from getting in the inside. The lid will also have the LCD
display and keypad attached to it (5). On the next layer inside of the housing there will be
three slots to hold each chemical reservoir (6) and also the electronic components (7).
The electronic components will include the battery, microcontroller, and the probes.
From the micro controller, there is a probe tunnel (9) that stems into the bottom of the
device so that the probes can touch the water to receive the necessary readings. Based on
these probe readings, the reservoirs will release the correct amount of chemicals needed
into the water by the servo gate actuation system. The servo (10) will be inside the
reservoir sitting on the top gate (11), which has holes in them. The bottom also has holes
that are misaligned when the system is not running. When the actuation system is
operating, the holes from the top and bottom will align and the chemicals will be released
from the reservoir.
VII. Embodiment Design Process
Product Architecture
The overall final design of our product will be based on a hemispherical shape,
with the spherical portion in the water and the flat portion protruding from the water. The
53. 53
various modules will be assembled together along an axis, perpendicular to and
going through the center of the assembled product. The overall architecture will maintain
radial symmetry around this axis as well. This type of architecture will help in the overall
stability and buoyancy of the product in water by distributing weight radially over the
bottom surface. Furthermore this type of architecture will help in assembly
and maintenance of the product since most interfaces will be concentrically attached and
easily separated. Furthermore our design and implantation of this product will be of an
integral architecture, since many components will rely on other components to perform
their tasks. This duality does not allow for us to maintain a modular architecture. For
example, if we made our product of a modular architecture, we could have had
different modules that came together and tested for and dispensed different chemicals.
This way the customer could decide specifically which module they wanted to purchase
to create their array. But this type of architecture was not possible since the testing of the
chlorine depends on the pH of the pool. Therefore components had to be included into on
system since they rely on each other and serve multiple purposes for other
components. The various modules of this product will be grouped into two main
systems, the Housing and the Electronics. The Housing will be the structural body of the
product that will be in contact with the water and hold the chemicals and electronics. The
Electronics will include all the circuits that will test for and deploy the chemicals. The
housing consists of four modules, the lid, reservoir cover, reservoir, and the foam base.
The electronics consist of the two probes and their circuitry, ORP and pH, the
microcontroller, the servos and gates, and the LCD screen and keypad.
54. 54
Configuration design
The following are the configuration design considerations and rational for our in
house designed parts.
The Lid
Figure 7.1: The Lid
The Lid will be the top most component in our product and it will be the main
component that the user interacts with. The Lid will need to attach to the rest of the
housing and provide a tight seal to prevent water for getting into the electronic
components and reservoirs. For the attachment to the rest of the housing, six latches will
be used around the rim of the Lid to secure it. The Lid will hold to the overall
product architecture and be of a circular shape and it will be the “flat” part of the
hemispherical shape. The Lid will also have to allow for easy retrieval and deployment of
the product from and to the pool. Therefore the Lid needs to have a handle on the top of
it. This handle must be big enough and have enough spacing from the Lid to allow for a
tight grip. According to A Guide to Selecting Non-Powered Hand Tools the widest part of
your hand is usually 4” – 6” and ideal handle diameter is 1.25” to 2”.[B.3]. Once the Lid
is removed from the housing by the user, it will expose the electronics and the reservoirs,
55. 55
therefore allowing the user to change the battery or refill the reservoirs. But once the Lid
is closed the reservoir and the electronics must be sealed off from each other, therefore
the bottom of the lid will have reservoir seals to keep a barrier from the Lid and the
electronics.
Reservoir Cover
Figure 7.2: Reservoir Cover
The Reservoir Cover is the next component under the Lid.
The Reservoir Cover will close off the reservoir from the rest of the assembly and allow
for an opening to refill the reservoirs. The opening will be big enough to allow for the
chemical containers to fit. The Reservoir Cover will also be the base for which the
electronics, like battery and controller, sit on. A hole in the middle of the Reservoir
Cover will allow for the probes to reach the water through the
middle. The reservoir Cover will be attached to the Reservoirs through ultrasonic
welding and the Lid will simply rest on top.
56. 56
Reservoir
Figure 7.3: Reservoir
The Reservoir is the main and largest component of the Housing assembly. It sets
the overall dimension of the product and dictates the dimension of the other components
as well. There will be three sections, each holding a different chemical and separated
from the other by a wall. The Reservoir is configured in a radial design with a center
tunnel that runs through it. This tunnel is an access for the probes and is sized to allow a
comfortable fit for both probes. In all three sections, close to the center of the Reservoir,
holes are placed to be the exit point of the chemicals. The inner base of the Reservoir is
angled 10° toward the center so the chemicals flow to the exit point. The individual
reservoirs are sized to hold a volume of approximately 2.5L and made a little larger to
allow for space. This value was chosen after careful consideration of the amount of
chlorine used since it is the most used chemical in pools. A standard size that chlorine
refills come in is 5 lbs (2.48 L) which will last a 10,000 gallon pool well more than a
month [B.11]. This parameter sets the overall diameter of the housing 10 be about 18 in.
57. 57
Foam Base
The Foam Base will be the last portion of the assembled housing, and it will be in
direct contact with the water. The Foam Base will serve two main purposes. First, it is
light weight, so instead of plastic, a heavier material, taking up the large portion of the
empty space on the bottom of the product to complete the circular shape, a material made
of foam can accomplish that while adding insignificant weight. This keeps our product
under our weight requirements. Secondly, the lower density of the foam will help
in buoyancy. The Foam Base will be shaped in a way to complete
the hemispherical shape of the product.
DFM/DFA/Logistics
When considering the Design for Manufacturing (DFM), all PBT plastics have
excellent specs to be injection molded. During the injection molding process, the
shrinkage rate is very low (0.010 in/in) and has a fast crystallization process making it
easy to mold [B.10]. As stated above, the resin to create the molded components is cheap
to buy in bulk, and if the parts are molded in a single shot, many parts can be produced
continuously with minimal oversight or manpower. The biggest costs would be the
machine itself, and the mold to create the component. After those two considerations are
taken care of, many parts can be produced for minimal cost.
For Design for Assembly, considerations have been made to minimize the
manufacturing cost and time. The main body is composed of four main components: The
lid/handle system, the reservoir cap, the reservoirs, and a buoy. The lid/handle will be
made from PRL TP-FR-IM-(color)-3, and will latch onto the reservoirs with six separate
latches. This part can be removed with the intent that the user will refill the reservoirs
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when it is required. Next, the reservoir cap will be welded to the reservoir body, and both
of these components will be made of PRL TP-FR-IM-(color)-3 as well. At the bottom of
this assembly, a urethane foam will be attached via waterproof adhesive to the base of the
plastic reservoir body. In order to produce this part, three separate injection molded PRL
TP-FR-IM-(color)-3 components will have to be made. One will act as the lid/handle,
and two others will be welded together to provide a housing for the chemicals. A
urethane foam can be purchased in bulk and can be attached to the base of the assembly.
In order for the assembly to work, manpower will have to be used to move the
components from the injection molding site to an assembly site, where team members
will individually weld the two attached components together and will attach the foam to
the bottom. Three separate molds will need to be purchased to produce these parts, and
the urethane foam will have to be purchased from a third party supplier.
An extra piece will be attached to the bottom of the reservoir container, above the
buoy which will act as a moving door. This servo will be attached to some circuitry,
which will be connected to a battery all within the body of the reservoir container. An
actuating servo will spin, resulting in the holes at the bottom of the reservoir to become
open when the program tells it to. The falling rates of the chemicals will be calculated
and tested so that the falling rates depending on the tested chemical levels of the pool will
be formulaic. The circuitry and the servo will all be entirely contained within the body of
the plastic, preventing it from becoming breached by either the chemicals or the pool
water. This piece can be assembled at the end of the production process via manpower in
an assembly line-like system.
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In the logistics department (Design for Logistics), a supplier would have to be
considered for the PBT resin to be shipped monthly to the warehouse where the injection
molding will be taking place, or if the decision is made to outsource the production of the
casing and reservoirs, then a supplier would have to be given technical drawings of the
parts required so that they can mold the components as a third party and sell it back to
Pool Systems Inc [B.1]. There would have to be a monthly quota for casings and
reservoirs which would probably change over the course of the year, meaning that the
outsourced manufacturing company would have certain months where they would need
to supply Pool Systems Inc. with more produced parts. Also, a supplier would be
required for the production of the molds. Since molds have a certain life span, new
molds would be required every several hundred thousand parts produced or so [B.1].
Pool Systems Inc. could outsource the creation of the mold to China to be produced, but
this would be sacrificing mold quality and mold life compared to a manufacturer within
the U.S [B.13]. A cost analysis would have to be performed to see which manufacturer
would be cheaper to work with over time. Due to the fact that a quote is required to get
an actual price for an injection molding machine and molds of a certain volume, a
specific number cannot be given in this report.
The designed parts will include the lid/handle piece, the reservoir cap, and the
reservoir body. If it is decided to purchase the injection molds and the molding machines,
then the only component that will need to be purchased is the resin pellets. However, if
the machines aren't purchased after a cost analysis, then the injection molded parts will
need to be purchased. This will require Pool Systems Inc. to outsource the molding job to
a third party company that specializes in injection molding. Also, this would require the
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declassification of proprietary information such as technical drawings and required
specifications/certifications. Urethane foam can be purchased and cut to the necessary
size and be attached to the bottom of the reservoir via waterproof adhesive. The circuitry,
battery, and the sensors will all be purchased components since it would not be feasible to
create robotic pH and ORP sensors from scratch simply for this product. Also, an LCD
interaction screen can be purchased from a third party supplier and can easily be
integrated into the circuitry so that the user can put in information about pool size. As
stated above, the purchased components can be attached via manpower since it will be
more feasible to have someone put the parts together by hand rather than having an
assembly line of automated machines putting these components together.
As stated above, a cost analysis would have to be performed to see what methods would
be cheaper over time: purchasing the injection molding machines and molds to produce
the products, or outsourcing the production of these parts to an injection molding
company. The machines themselves have a certain cost per hour, a cost to purchase, a
mold to purchase, maintenance costs, and manpower costs for workers, processing
engineers, molding engineers, and quality engineers who work on the factory floor to
ensure the parts are produced with customer standard quality, and do not have any other
physical or aesthetic defects [B.1]. Also, considerations would have to be made to either
purchase a newer model injection-molding machine from the 1970s or 1980s, or to
purchase a new machine for a much higher cost. If an older machine is purchased, the
cost would be significantly lower at the sacrifice of quality and machine life [B.6]. If the
machine requires significant amounts of maintenance due to its age, the final cost after
repairs and maintenance may outweigh the cost of a new machine in the end.
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Failure Modes & Effects Analysis
Failure mode and effects analysis, also referred as FMEA, is a systematic
approach in which a team of engineers can assess possible weak links in the design of a
product. Rankings are given after a set of questions is answered for each critical function.
These rankings are based off of three important criteria: the severity of the failure, the
probability to failure, and the probability of identifying the problem before it affects the
user. These three rankings are multiplied together to determine the risk priority number,
or RPN. The RPN is then used to determine the risk of a particular failure and thus, the
overall successfulness of the product.
At the conclusion of our failure modes and effects analysis, we located critical
components that must function properly in order for our product to perform its assigned
task. Unlike other innovations, the failure of this product will rarely endanger lives.
Instead, failing components will lead to the dissatisfaction of the customer. For this
reason, our risk priority numbers are rather low due to nominal severity ratings.
Nevertheless, there are a few specific areas we would like to further look into to prevent
future failures. Below are the highest risks for failure with a short explanation of why it
would occur and how it can be detected or prevented:
1. Sensors fail to gather correct readings
Occurrence: The reason for this failure could come from faulty sensors or
sensors falling out of calibration. Another possibility is that wires become
unfastened during use.
Detection: Since users might be unaware of this failure, we would like to
introduce ways to inform the user of faulty sensor behavior. The first
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approach is by providing a time frame for the user to recalibrate the sensors.
This information will be included in the instruction manual. Furthermore,
code will be implemented to send SMS alerts to the user if the sensors fail to
take readings.
2. Actuators add incorrect amount of chemicals
Occurrence: This failure will largely be influenced by the robustness of our
processing code. In addition, the servo specifications can affect the precision
and accuracy of the servo responding to the code.
Detection: Similar to above, a SMS alert system will be implemented to
measure the weight of the remaining chemicals compared to the previous
quantity. This value can be compared to the amount of chemicals that was
supposed to be added. If this comparison is vastly different or happens
frequently, the user will be notified.
3. Reservoirs leak chemicals
Occurrence: Failures of the reservoirs will occur during manufacturing. To
avoid the frequency of this issue, considerable thought has been used to
determine the thickness and material of the walls.
Detection: While it is hard for the user to notice a reservoir wall failure
without visual inspecting the product, we can provide guidelines for correct
operation. Common refill times for specific pool sizes will be included in the
instruction manual. While we know that the addition of chemicals will vary
for each pool and location, this provides a rough guide to determine incorrect
device operation.
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Below are moderate risks for failures with a short explanation of why it will occur and
how it can be detected or prevented:
1. The wrong chemical is placed in a reservoir
Occurrence: This failure is directly related to human contributions. Despite
having the reservoir lids labeled with the chemical they should contain,
humans inevitably make mistakes. If a user adds the incorrect chemical to a
reservoir, the system would assume that it was the correct chemical and add it
accordingly. This would inversely affect the balancing of chemicals.
Detection: In order to detect this, code will be added to determine which
chemical has been added to each reservoir. Assuming the reservoir is filled to
the max fill line, weight sensors and densities can be used to determine
chemical type. If the type is wrong, the user will be alerted with either LED
indicators or SMS warnings.
2. System fails to start
Occurrence: This failure can be caused by human contributions or
manufacturing. In terms of the human contributions, the user may forget to
recharge the batteries. In terms of manufacturing, a short circuit or water
damage may prohibit the device from starting.
Detection: In order to detect these failures, LED indicators and SMS
warnings will be used. In addition, average battery life will be included in the
instruction manual.
It should also be noted that FMEA also helped Pool Systems Inc. to determine a product
weight. If a user cannot pick up the product, the product is considered a failure.
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Therefore, we were able to use programs to test the difficulty of lifting objects of varying
weight and positions for a percentile of humans. This analysis will be examined in more
detail later in the report. A more exhaustive list of failures can be found in the FMEA
chart located in Appendix C.
Material Selection
The material that is chosen to provide the casing for the final product will be
Polybutylene Terephthalate (PRL TP-FR-IM-(color)-3). This material is a thermoplastic
polymer that is cheap and easy to manufacture into different shapes and sizes via plastic
injection molding.
The reason that PRL TP-FR-IM-(color)-3 is chosen to be used as the casing
material is that it has high impact resistance, the resin pellets are easy to purchase and
easy to manufacture, the material itself is easy and cheap to manufacture via plastic
injection molding continuously [B.1], it has a high yield strength for a thermoplastic, has
thermal properties that will be able to withstand any pool or spa operating temperature,
and has a high UV resistance [B.10]. Due to the nature of the production of the material,
all a manufacturer would have to do is purchase a mold for the casing and purchase the
PBT resin to produce the parts. Because this part would be manufactured via plastic
injection molding, minimal oversight would be required to operate the molding machine,
and assuming this would be a one shot tool (due to the size of the casing), you would not
need manpower to separate the part from a runner and sprue, meaning no surface defects
would be present due to the absence of a gate [B.1].
Once the part is manufactured, it will have a high Tensile Strength (6500 psi) and
a large Flexural Strength (11300 psi) and Flexural Modulus (300,000 psi) [B.10]. This is
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an important factor to consider for part production because human error is a large part of
the consideration for the design. If the user were to accidentally drop this product, it
would not be preferable for the casing to break, exposing the circuitry and chemicals. It
is for the user’s benefit that the material is durable and can withstand being dropped or
accidentally stepped on during the chemical refill that will have to be performed.
Another consideration was a large range of temperature resistances. The material will be
able to withstand all of the operating temperatures of a pool or a spa, and if the user
happens to leave the product out in the sun, the material will still be very far away from
its melting point.
Finally, PRL TP-FR-IM-(color)-3 has an outdoor suitability of f2 based on the UL 746C
Standard for Safety of Polymeric Materials guidelines [B.10]. This means that it has a
high UV resistance and has passed the water exposure/immersion testing [B.13]. The
material was tested for flammability, mechanical impact, and mechanical strength both
before and after testing and was able to pass both in accordance with Test Standard
protocol [B.13].
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Parametric Design
The overall diameter of the Lid was chosen to be 18” for it to close off the
product completely. The lower portion of the Lid, which will be inserted into the housing,
was chosen to have a diameter of 17.46” with a tolerance of -0.02” so that it may be a
clearance fit with a clearance of 0.02” with the Reservoir opening. Similarly the reservoir
seal, on the bottom of the Lid, were sized up to fit into the reservoir opening and position
as to be concentric with the openings when the lid is placed. The reservoir seals will be
3.960” in diameter with a tolerance of -0.02”, and three of them are placed in a circular
pattern 5” from the center. The seals and the two sections of the Lid will each have a
thickness of 0.25” as to remain consistent with the overall product thickness and to be
thick enough to insert into the housing. As for FEA, this thickness is shown to be
sufficient to keep minimal deformation. There isn’t very much choice with the
parameters of the handle since it is set by ergonomic standards. The handle will have a
cross-section of 0.75” by 1.5”, be 6” long, and have a clearance from the Lid of 1”.
Figure 7.4a and 7.4b show the FEA analysis on the lid, simulating the lifting of the
product off the ground and assuming full chemical reservoirs. The von Mises stress is
nominal throughout the surface of the Lid and only spikes up to 350 psi, well below the
yield strength of the material, at the corner of the Lid and handle. The max deformation is
seen to be about 0.005” at the outer edges of the Lid and even more insignificant at the
center, so it is not seen as a factor.
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Figure 7.4a: Stress Distribution of Lid, von Mises (psi)
Figure 7.4b: Deformation of Lid (in)
The stress concentration at the corner of the handle and lid surface can be reduced
by the implementation of a fillet feature at the interface. The fillet can be varied to
determine an ideal value but cannot be made too big as to dominate the shape of the
handle. A sensitivity design study was preformed to determine the fillet. Figure 7.5 shows
the results of this parameter variation. As the fillet size increases the stress decreases and
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seems to approach a value of 200 psi, but the fillet cannot be made larger than 0.5” since
it will become too big. Therefore a value of 0.41” is chosen; thus reducing the stress to
approximately 250 psi.
Figure 7.5 Sensitivity Design Study for fillet.
The Reservoir is the main component of the product and its dimensions drive the
dimensions of all the other parts. The Reservoir is designed so that each section of the
reservoir is approximately 2.5L. First we picked the thickness of the Reservoir,
considering overall product rigidity, need for low weight, and the injection molding
process, a thickness of 0.25” with tolerances of ± 0.01” was determined, later FEA
analysis shows this thickness is sufficient. Since a radial architecture was chosen earlier,
a certain amount of arc must be revolved around the symmetry axis to reach the desired
volume, modeled by this equation V = (Revolved Area)*(Radius from axis of symmetry
to center of revolved area * 2)π. After varying the radius of the cross sectional semi-circle
and depth of the reservoir section, an cross sectional area of 16.891in2
was determine,
which when offset from and revolved around the symmetrical axis gave each chemical
reservoir 2.5L. From this determination the radius of the hemispherical dome was 6”
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offset form the symmetry axis by 3”, therefore giving the overall diameter of 18”. Figures
7.6a and 7.6b show the stress and deformation distributions on the structure of the
reservoir as it is fully filled with chemicals and resting on the ground.
Figure 7.6a: Stress Distribution, von Mises (psi)
Figure 7.6b: Deformation Distribution, (in)
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The stress throughout the Reservoir is well below the yield strength of the
material and the deformation is almost nonexistent throughout the component, therefore
justifying our selection of 0.25” as the component thickness.
The Reservoir Cover was given a similar thickness of 0.25” with tolerances of ±
0.01”. This component needs to fit into the housing so it must have a clearance fit with
the reservoir. Given a clearance of 0.02” the Cover was sized to a radius of 8.729” with
tolerances of -0.02” to fit inside. The reservoir openings were sized to 4” with a tolerance
of +0.02” to correspond to the chemical containers and fit with the covers on the Lid, and
made 0.98” in height to give a clearance when the Lid is closed.
The shape of the Reservoir dictates the Foam Base’s configuration since it is there
to complete the hemispherical shape. The Base has a cross sectional area of 6.979in2
and
is offset from the symmetry axis by 3” so it can fit around the bottom half of the
Reservoir.
IX. Prototyping & Testing
Determining the target weight of the system
We used the University of Michigan 3DSSPP 6.0.6 program and the NIOSH
Lifting Equation simultaneously to find a target weight for our system. Within the
3DSSPP program, we selected the 5th
percentile in order to account for 95% of all people.
Seeing how our product is being created for the end user in mind, it is critical that a large
portion of our market be able to utilize our product on a daily basis. From this, we tested
various weights to determine what percent of the population had the strength to lift an
object in certain conditions. The conditions we tested involved the squat and stoop lift
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with a weight attached to the right arm. It is to be noted that we tested both hands but the
results were similar, therefore the right hand was chosen for simplicity. We feel that these
positions and hand placements will be the preferred method to add or remove our device
from pools. The reasoning behind this is that the product will be stationed around feet
level. Using these conditions, different weights were analyzed for both males and
females. The limiting strength factor was recorded for each combination. While there
may be individuals that can still lift the object despite a specific muscle limitation, we are
looking at the extreme values to account for all individuals. From the results in Table 9.1,
we would like to have our product to be around 30lbs, however, we feel comfortable that
if our product is around 40lbs we will still satisfy a large portion of our market. It is clear
that if our product increases to 50lbs, we risk losing a large portion of our female market.
Pictures of the two positions and analysis of the 40lb target weight can be seen in
Appendix D.
Gender Percentile Position Height Weight System
Weight
Minimal Strength
Percentile
Male 5 Squat 63.8 132 30 89%
Female 5 Squat 59 110.9 30 76%
Male 5 Stoop 63.8 132 30 91%
Female 5 Stoop 59 110.9 30 85%
Male 5 Squat 63.8 132 40 85%
Female 5 Squat 59 110.9 40 40%
Male 5 Stoop 63.8 132 40 90%
Female 5 Stoop 59 110.9 40 77%
Male 5 Squat 63.8 132 50 69%
Female 5 Squat 59 110.9 50 13%
Male 5 Stoop 63.8 132 50 87%
Female 5 Stoop 59 110.9 50 58%
Table 9.1: Product weight analysis
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NIOSH Lifting Equation
The other approach we had used to determine an efficient target weight for our
device was the NIOSH Lifting Equation. According to Ergonomics Plus, the NIOSH
Lifting Equation is “a tool used by occupational health and safety professionals to assess
the manual material handling risks associated with lifting and lowering tasks in the
workplace” (Middlesworth). We decided to apply this tool to our design to see if our
target weight of 40 pounds is a safe weight to be lifted. The two lifting tasks we
considered was lifting the device from pool to ground and also lifting it from the ground
to the pool. We first had to consider nine different lifting variable including horizontal
location (H), vertical location (V), travel distance (D), angle of asymmetry (A), coupling,
frequency, average load, maximum load (L), and the duration. After we assign these
variables a value, we must then use multiplier tables that are provided by the NIOSH
tool. Lastly, we are able to determine a Recommended Weight Limit (RWL) and
compare it to the maximum load (L) to see if our target weight is risky or not to our
customers. This comparison is called the Lifting Index (LI) and if that value is greater
than 1, then the customers could face possible injuries.
In Table 9.2, we assigned the values to each lifting variable for both tasks. The
horizontal location measures how far from a user’s body will the object be when they lift
it so we estimated roughly that H = 9 inches for both tasks. The vertical location
measures how high the user’s hands will be from the ground when the device is in its
preferred position. For the pool to ground task, V = 5 inches and for ground to pool task,
V = 2 inches. The distance traveled is how far the device will be carried from its vertical
location. For the pool to ground task, D = 12 inches and for ground to pool task, D = 3
73. 73
inches. The angle of asymmetry is how far the user needs to twist their body to perform
the task. Both tasks got an estimate of a 20-degree twist. The coupling value has to do
with the hand connection between the user and the device. A 1 value denotes that there is
a good connection because of the handle design. The frequency has 0.2 lifts per minute
value because the user should only have to lift this device twice during an average 15
minute sampling time. 0.2 lifts per minutes is the minimum value that this variable can
have. The average and maximum loads will always be 40 pounds since that is the target
weight. Last, the duration value is 1 because the time to perform these tasks is considered
short due to the time being less than one hour.
Table 9.2: NIOSH Lifting Variables
After we assigned all of the values for the lifting variables, we then could use
the multiplier tables found in the Applications Manual For The Revised NIOSH Lifting
Equation (16-31, Garg, Putz-Anderson, and Waters). Based on the lifting equation values,
there is a multiplier value that corresponds to those values. The multiplier values can be
found in Table 9.3 and Table 9.5 below. From these values we then can calculate the
RWL. The equation for the recommended weight limit is:
RWL = LC x HM x VM x DM x AM x FM x CM
LC is considered the load constant, which is always 51 pounds for this equation. After the
RWL is calculated, the LI can be calculated by:
LI = L/RWL
Table 9.4 and Table 9.6 below show that both tasks receive similar LI values of 1.07,
which is greater than 1. From these values we can conclude that there will be a greater
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risk involved lifting this device that is 40 pounds, but it also is not much greater than 1.
Therefore, 40 pounds can be lifted, however, we will attempt to design our product much
lighter to eliminate possible injuries from heavy lifting.
Table 9.3
Table 9.4
Table 9.5
Table 9.6
The final prototype will be a physical model of our product that will be tested in
how well it will perform our main function. These results will be used to validate the
decisions that our team has made along the way. The team’s overall plan for the final
prototype is to construct an operational device that will float in a predetermined body of
water while performing its main function.
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Key functionalities demonstrated
The main function that the device demonstrates is completing a read and react
cycle. However, due to an inadequate microprocessor along with a lack of suitable power,
the steps had to be segmented. The user had to perform some steps in order for the device
to function. The first step by the device is the sensing of the water's chemistry. Two
sensors, the pH and the ORP sensor do this. These take readings of the current pH levels
and the Oxidation Reduction Potential of the water. The sensors then transmitted these
readings through the circuit to the microprocessor, which will interpret the reading and
calculate an output. The output will determine how much chemical material shall be
dispersed into the pool water. The Arduino cannot successfully take the data from the two
circuits and use them both for interpretation for an output. We could individually take the
pH levels and the ORP levels of the water. In order to determine the chlorine of the
water, the program needs pH level, temperature of the water and the oxidation-reduction
potential. Since the Arduino could not take the input of both the sensors at the same time,
we had to focus on the pH portion of the program. After the pH was read the Arduino
knew how much chemical material to add to the water based on the program the team
wrote for it. The application of material was done by the actuation of servomotors. The
gates that allowed the material to fall into the water were holes that were covered by the
servomotor. When the servo was rotated the holes opened, thus dumping material into the
water. The actuation process works very well. The servos were glued to the platform that
holds the chemicals. The hole that allows for the chemicals to pass through the platform
was drilled next to the servo. Attached to the servo is a gate. The gate prevents the
chemicals from entering the water. The Arduino controls the servo and thus the gates.
