urban home farming in singapore - herschelpangborn.com · the purpose of this report is to present...

ME4263 Product Design

Project Report

Urban Home Farming in Singapore

June 08, 2012

Submitted by:

David Blyton

Herschel Pangborn

Li Weiyan

Liu Dong

Liu Yisi

Product Design: Urban Farming in Singapore

1

Executive Summary The purpose of this report is to present a product designed to assist with urban home

farming in Singapore. The product integrates a moisture sensor and water level

monitor, designed to create a carefree solution to urban farming by reducing the time

investment of watering so as to attract more city dwellers to start growing plants

indoors, and to allow them to produce healthier plants in les time. An Arduino Uno

R3 microcontroller was used to generate a prototype, which controls the measurement

of moisture level in soil as well as water level in water tank and can activate a pump

to water the plants. Electrical resistance of the soil is inversely proportional to the

moisture level, and a critical resistance corresponding to the point at which a plant

needs to be watered can be identified based upon the type of soil and plants, and

fine-tuned by the user. When this critical resistance is reached, the Arduino activates a

water pump and water is pumped from water tank to irrigate plants. The Arduino also

controls a physical user interface, consisting of three status LEDs, a tank refill push

button, and a moisture level adjustment knob.

This report covers the product design process including customer need identification,

concept generation and selection and financial justification. The report also

investigates several limitations of the prototype, such as the accuracy of moisture

measurement and methods of user notification. Further improvements include

developing multi-sensor for different types of soil and creating web interface that

allows the sending of notifications to users through email, Facebook, or iPhone and

Android apps.


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Introduction

Singapore’s approach to food security is primed to undergo a fundamental shift –

from being a passive food-importer to a more active contributor to the regional food

system. Certain realities clearly define food security planning: Singapore is not an

agricultural country as it has little land to grow its own food, thus it is perpetually

subject to the influences of foreign nations. This picture may soon change if

Singapore’s highly urbanized domestic market could be turned into a ‘test lab’ for

urban farming.

Urban farming refers to agricultural production that takes place within the urban

region, which includes growing of food, medicinal plants, and ornamental plants.

Having found that a lack of motivation, either due to time investment or perception of

the worth of that time, is the main reason that drives Singaporean away from home

farming, the designers aim to develop a product that will require little to no time

investment through the usage of an integrated system that monitors and sustains a

plant as it grows.

Field interviews at a

Singapore HDB residence

were conducted to better

understand the customer

needs. Listed in Table 1

are the ten primary needs

that are to be addressed,

among which space

efficiency, easy

installation, low maintenance and low power and water demand are of highest

Table 1: Customer needs and the importance of each need with 1 being the most important and 5 being the least important.


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importance. The design team interpreted these need and generated need-metric chart

shown in Table 2. Eight out of the 10 needs can be quantified by at least one

parameter. In order to ensure the customer’s satisfaction, the team developed

functional specifications for each metric -- the final product is expected to be within

the size of 30×100×50 cm in order to fit in a common balcony of an HDB apartment

(see Appendix I); it requires less than 20 minutes to install and less than 5 minutes to

maintain the whole system per week; furthermore, power needed to run the product

should be around 400 W-hr per week, which is equivalent to the power consumed by

a 40-watt light bulb in 10 hours.

Met

ric

Dep

th a

nd h

eigh

t

Tim

e to

pro

duce

a e

dibl

e pl

ant

Tim

e re

quire

d fo

r mai

nten

ance

Tim

e re

quire

d to

inst

all a

nd re

pair

Tool

s nee

ded

for i

nsta

llatio

n an

d m

aint

enan

ce

Pric

e

Pow

er c

onsu

med

per

wee

k

Am

ount

of w

ater

con

sum

ed p

er w

eek

LED

/aud

io sy

stem

Sing

apor

e N

atio

nal

Envi

ronm

ent

Age

ncy

Stan

dard

s

# Need # 1 2 3 4 5 6 7 8 9 10

1 Space efficient ●

9 Capable of facilitating the growth of a plant

●

3 Low maintenance ●

2 Easy to install and repair ● ●

5 Inexpensive to purchase ●

4 Low power and water demand ● ●

7 Gives indication or instructions when needed

●

8 Use of recyclable materials ●

Table 2: Need-‐metric chart


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Product Design Process & Solution

Having generated customer

needs and linked these to metrics,

the team was ready to develop a

solution to fulfill the mission

statement. The first task was to

further define the scope of the

product. This was accomplished

through the use of a black box

model, presented in Figure 1. It

was determined that the system

would need to deliver water and

energy to the plants, as well as

energy to any electronic systems.

System conditions would also need

to be translated into information provide to the user. The black box model was

elaborated upon through the use of a functional diagram (Figure 2), in which the basic

tasks demonstrating the relationship between inputs and outputs to the product are

outlined. One can observe that system conditions play a role in the activation of the

pump—specifically, when the soil is dry.

Once the basic functions and interactions that would need to be designed had

been identified, the team could pursue concept generation. This was accomplished

through both internal and external searching. The external search revealed that

automated home gardening systems have been created and documented on the internet,

but that they primarily exist as DIY projects requiring extensive knowledge of

electronics and computer programming, as well as access to soldering tools and a

variety of electronics parts. These prerequisites obviously present a significant

Figure 2: Functional Diagram

Figure 1: Black Box Model


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barrier to consumers, especially given that customer needs identified previously

included the need for the system to be quick and easy to set up, as well as relatively

inexpensive and easy to operate. Additionally, existing systems found online lack the

implementation of a simple user interface. One such system, named Garduino,

exemplifies these traits. However, these systems do serve as a great resource in

order to study the solutions that others have chosen in order to solve similar problems

within gardening automation.

Figure 3: Concept Screening Matrix

A patent search was also

conducted as part of the

external search. However, this

did not reveal a great deal of

prior art relating to automated

home gardening. This

suggests that there is a market

opportunity for the product.

After gathering external

data, the team worked both

individually and as a group to Figure 4: Selected Concepts Sketched


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brainstorm concepts to fulfill the needs identified previously. One function that

received a great deal attention was the method of measuring the amount of water

available in the system’s storage tank. Four concepts were used in a

concept-screening matrix (Figure 3). These were: A “toilet bowl” sensor, which

would use an object’s buoyancy to trigger a switch, electrical leads that detect when

they are submerged, an ultrasonic transducer that can detect the water level, and the

use of the microcontroller to monitor the run-time of the pump given that its total

capacity has been measured. The screening matrix strongly suggested that the

“run-time” concept was the best for the design. In fact, this concept scored so much

higher than the others that concept scoring was not required in this instance.

The team also devoted a

significant amount of time to the user

interface. While a simple physical

user interface consisting of LEDs,

buttons or dials would be more

practical to implement for

prototyping, a mass production model

could utilized a web-enabled system

that emails users when it is time to

pollinate or refill the water tank and

allows them to input information about the type and quantity of plants they are

growing so as to optimize the system’s behavior. These features would serve to

increase the product’s “cool factor,” allowing youths to relate better to gardening

because of the incorporation of modern technology. They also provide the product

with a competitive advantage over traditional watering methods and competing

products. An early sketch of the selected design is presented in Figure 4. One can

observe the microcontroller acting as the “brain” of the system, monitoring both soil

Figure 5: CAD Model of Design


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Figure 6: Circuit Diagram for Alpha Prototype

moisture (via resistance measurements across a two pieces of metal embedded in the

soil) and the tank water level, activating the pump via a relay, and coordinating the

operation of the user interface. A CAD model of the design is presented in Figure 5.

One can observe that the user interface box is attached to the exterior of the water

tank, and that solar panels to run the electronics are mounted on the lid of the tank.

While the internal systems of the product are relatively complex in terms of

electronics and computer programming, the interaction between the user and the

system is very simple, largely due to considerations of industrial design. The

physical user interface (not including any web-based service) consists of only three

LED lights, an adjustment knob, and a button. The green LED informs users that the

system is in fine working order. The yellow LED signals that the tank is low on

water. The red LED indicates that the tank is on empty and needs to be refilled.

After refilling the tank, the user presses the button to reset the system. The

adjustment knob can be used to adjust the moisture level maintained in the soil in

order to keep the soil either drier or wetter. This allows the user to fine-tune

operations if need-be after the web interface calibrates the system to the types of

plants in the garden.

The final product will be

comprised of two main

sections: The water storage

tank and the control panel.

The tank will be constructed

through plastic injection

mold. The lid will use a

similar process, but two

small holes will be featured

for hoses and wires. The tank


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and lid will be designed in such a way that they can snap shut without the use of

fasteners. The pump will attach to the interior of the water tank with suction cups. The

suction cups will eliminate the need for fasteners, as well as allow for modification.

The user could easily transport the pump to a larger or smaller tank if the original one

did not suit their needs. The control panel will also be created from plastic injection

molds, forming parts that snap together. A circuit board housing all the internal

electronics as well as LEDs and controls will also snap into the interior of the control

box. Unobtrusive access holes in the panels will allow wires to attach to the solar

panel and water pump. The control box, along with the pump and all other materials

included with the product can packaged inside the water tank when the product is sold,

allowing shipping and packaging costs to be minimized.

An alpha prototype of this design was constructed through the use of an Arduino

open-source microcontroller. A circuit diagram of this prototype is given in Figure 6,

and a bill of materials is available in the appendix. This system required a power

outlet in order to run the pump, however future iterations of prototypes would use

lower voltage pumps that could be run on exclusively solar power. However,

construction and successful operation of the prototype demonstrated that the design is

viable. The Arduino was able to monitor the moisture levels in the soil via resistance

using a voltage divider, and could activate the pump when the resistance dropped

below a threshold. The run-time of the pump was continuously tracked, so that when

the tank was low on water, the system would pause operation until the tank was filled

and the button on the user interface was pressed. The prototype was also able to send

some basic information to a computer over a USB connection, allowing the user to

see the threshold value used in the moisture sensor, the remaining amount of water in

the tank, and well as how long it had been since the tank was last filled. All that

would remain in order to make this information available on the internet would be to

add an inexpensive wifi chip to the hardware so that the data could be uploaded to the


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web and then downloaded and distributed to users’ email or smartphones via iPhone

and Android apps. Future prototypes would incorporate a proprietary microcontroller

in place of the Arduino board, as well as more robust circuitry to make the system

resilient to power surges and other unexpected phenomena.

The cost of a mass production model has been estimated to be $40. Table 3

provides a break-down of the estimated cost of each part of the design. A

microcontroller developed and manufactured especially for this product would be a

fraction of the cost of a commercially available version. Its components would be

tailored to fit the specific functional requirements of the system. By far the most

expensive part of the design will be the solar panels. Although these panels effectively

double the price of the product, they are a necessary component because the potting

beds for which the product is primarily designed do not have electrical outlets nearby.

In fact, the closest source of electricity other than the sun is on the other side of a

sliding door.

Item Cost

Water pump $5

Microcontroller $5

Electronic components $5

Water tank & control box enclosure $5

Solar panels $20

Total $40

Table 3: Cost breakdown of mass production model


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Financial Justification

The product life cycle is estimated to be four years without upgrading the electrical

components. Heavy investment on advertising will be made in the first two years in

order to gain market share until the product reaches its maturity in the third year.

Sales are expected to decline from year four onwards due to increasing competition

and market saturation. An exit strategy, such as introducing an upgraded version of

the product, may then be considered. As shown in Table 5, the product is estimated to

break even in year two after launching the product. The net present value of luaching

the product in the first four years is SGD 452,012, which is reasonably profitable.

Table 4: Selling price and number of unit sold throughout the product life cycle.

Market Year 1 Year 2 Year 3 Year 4

Selling price (S$) 80 80 80 80

Cost (S$) 40 30 25 25

Profit margin (S$) 40 50 55 55

Unit sold 3600 6480 7920 5750

Fiscal Year 2011 2012 2013 2014 Revenue 288,000.0 518,400.0 633,600.0 460,000.0 Cost of Goods Sold 144,000.0 194,400.0 198,000.0 143,750.0 Gross Profit 144,000.0 324,000.0 435,600.0 316,250.0 Selling/General/Admin.Expenses 5,000.0 7,000.0 12,000.0 7,090.0 Research and Development 50,000.0 - - - Marketing 80,000.0 80,000.0 60,000.0 40,000.0 Equipment 40,000.0 10,000.0 - - Interest Expense 24,480.0 55,080.0 74,052.0 53,762.5 Other Expenses 10,000.0 10,000.0 10,000.0 10,000.0 Total Operating Expenses 209,480.0 162,080.0 156,052.0 110852.5 Income Before Tax (65,480.0) 161,920.0 279,548.0 205,397.5 Income After Tax - 129,536.0 223,638.4 164,318.0 Net Income (65,480.0) 129,536.0 223,638.4 164,318.0

Table 5: Balance sheet


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Conclusion

Singapore is faced with potential food security issues, and urban farming has

promise to play a significant role in alleviating that risk by allowing urban residents to

grow their own healthy food inexpensively. However, in order to popularize the use

of urban farming, consumers need to be encouraged to give it a try. Having

identified that reducing the time investment required to grow plants is a primary

customer need, the team went through concept generation, selection, finalization and

financial justification and came up with an integrated electronic irrigation system that

keeps track of the moisture level of a plant as well as the water level in a water tank

so as to notify users when watering is needed and to reduce labor input to a minimum.

Although there are certain aspects of the product that require further development and

improvement, the design is capable of satisfying the customer needs and has

promising results as a profitable product. Above all, the team hopes that the design

might be capable of attracting more people to urban farming.


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Appendix 1: Typical balcony of an HDB apartment

Appendix 2: Soil Resistivity Measurement


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Appendix 3: Prototype Bill of Materials

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