Automatic Fish Feeder Final Report

beaverswimmingAI and Robotics

Nov 14, 2013 (3 years and 5 months ago)

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University of Victoria

Department of Electrical and Computer Engineering

ELEC 499
A



DESIGN PROJECT





Automatic Fish F
eeder


Final Report






Submitted by
:


Patrick Audet
paudet@uvic.ca

Tomas Martin
tlcmo@uvic.ca


November 14, 2013

Submitted to: Amirali Baniasadi Ph. D. (Supervisor)
Automatic Fish Feeder



Final Report



II




Patrick Audet / Tomas Martin



©20
05

T
ABLE OF
C
ONTENTS

1.

Executive Summary

................................
................................
................................
............
1

2.

Introduction

................................
................................
................................
.........................
2

3.

Market analysis

................................
................................
................................
...................
3

3.1

Product Definition

................................
................................
................................
.....
3

3.2

Analysis of the pet products market

................................
................................
..........
3

3.3

Competing products

................................
................................
................................
..
4

4.

Mechanical Design

................................
................................
................................
.............
5

4.1

Thermoelectric cooling devices


Seebeck effect

................................
.....................
5

4.2

Thermoelectric cooling system design

................................
................................
......
6

4.3

TEC Calculations

................................
................................
................................
......
8

4.4

TEC selection criteria

................................
................................
................................
9

4.5

TEC cooling

system design

................................
................................
.....................

11

4.6

Housing and feeding system

................................
................................
...................
12

5.

Electrical Design

................................
................................
................................
...............
16

5.1

Component selection

................................
................................
...............................
16

5.1.1

LCD Display

................................
................................
.............................
16

5.1.2

Microcontroller

................................
................................
.........................
17

5.1.3

Stepper Motor

................................
................................
...........................
19

5.1.4

Motor Selection
-

Bipolar stacked (1 W/coil)

................................
............
21

5.2

Power requirements

................................
................................
................................
.
22

5.3

Microcontroller selection

................................
................................
........................
22

5.4

Electrical schematics

................................
................................
...............................
24

5.5

Sof
tware

................................
................................
................................
..................
26

5.5.1

Main module:

................................
................................
............................
26

5.5.2

Set module:

................................
................................
...............................
26

5.5.3

Motor
movement:

................................
................................
.....................
27

6.

Product costs

................................
................................
................................
.....................
28

6.1

Bill of Materials

................................
................................
................................
......
28

6.2

To
tal costs and expected selling price

................................
................................
.....
29

7.

Conclusions
................................
................................
................................
.......................
30

8.

Recommendations

................................
................................
................................
.............
30

9.

References

................................
................................
................................
.........................
31

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Final Report



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Patrick Audet / Tomas Martin



©20
05

L
IST OF
F
IGURES

Figure 1:

Household breakdown by pet type

................................
................................
.........
3

Figur
e 2:

Automatic feeder types and prices (5)

................................
................................
...
4

Figure 3:

Seebeck Voltage diagram (7)

................................
................................
.................
5

Figure 4:

Thermocouples connected in series

(10)

................................
................................
6

Figure 5:

Schematic of a thermocouple (9)

................................
................................
...........
6

Figure 6:

Parameters used in mathematical equations (12)

................................
...................
8

Figure 7:

Performance of selected TEC (13)

................................
................................
.........
9

Figure 8:

Tellurex TEC dimensions (13)

................................
................................
.............
10

Figure 9:

Diagram of performance vs. Input power (8)

................................
......................
10

Figure 10:

TEC Cooling Overview

................................
................................
...................

11

Figure 11:

Picture of TEC Assem
bly

................................
................................
.................

11

Figure 12:

Mechanical drawing

................................
................................
.........................
13

Figure 13:

Automatic fish feeder housing and heatsink assembly

................................
....
14

Figure 14:

Automatic fish feeder
-

fully assembled

................................
..........................
15

Figure 15:

Structure of a transmissive LCD display (16)

................................
..................
16

Figure 16:

HD44780
-
based 2x16 character display

................................
..........................
16

Figure 17:

Unipolar motor structure (17)

................................
................................
..........
19

Figure

18:

Bipolar motor structure (17)

................................
................................
............
19

Figure 19:

Bipolar motor structure (17)

................................
................................
............
20

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Final Report



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Patrick Audet / Tomas Martin



©20
05

Figure 20:

Stacked stepper specifications (Danah
er Motion)

................................
...........
21

Figure 21:

BS2
-
SX Module schematic

................................
................................
..............
23

Figure 22:

Automatic fish feeder


electrical block diagram

................................
............
24

Figure 23:

Electrical Schematic
................................
................................
.........................
25

L
IST OF
T
ABLES

Table 1:

TEC Parameter Definitions

................................
................................
....................
8

Table 2:

Microcontroller characteristics (all prices in US$)

................................
..............
18

Table 3:

AFF Power requirements

................................
................................
.....................
22

Table 4:

TEC Input/Output requirements

................................
................................
..........
22

Table 5:

AFF Prototype


Material Costs

................................
................................
..........
28


Automatic Fish Feeder



Final Report

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Patrick Audet / Tomas Martin



©2005

1.

E
XECUTIVE
S
UMMARY

Pet ownership has been increasing at a steady

pace in the last 20 years.
In the

US, a
fter dogs and
cats, the most popular pet is
now
the freshwater fish.

More than 60% of households in the U.S. own a pet, and with pet ownership considered by many as
an affordable luxury, it is not surprising to see t
hat the total value of the pet industry approaching 35
Billion U.S. dollars (U.S. figures)

The Automatic fish feeder (AFF) is a product that focuses on this market. Its purpose is to dispense
frozen fish food into an aquarium, automatically, and for up to
14 days.

This document provides a brief outlook on possibilities of the AFF in the market: It e
xplores the total
customer base, looks at competing products
and the preferred distribution channels or points of sale.

The mechanical design for a prototype uni
t
, design and selection criteria for thermoelectric cooling,
electrical component descriptions and
complete electrical diagrams are also inclu
ded in this
document. T
he manufacturing cost is reviewed and compared to competitive products already on the
marke
t.

Recommendations are made to improve the thermal insulation of the design, select a less
complex
microcontroller

and lower cost through mass production.

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2.

I
NTRODUCTION

Companion animals bring positive health effects to their owners; most commonly cited e
ffects are
reduced levels of stress, depression, and

even

heart risk. (1)

Mammals, especially dogs and cats, and birds have dominated the pet scene for a very long time.
Many of these are domesticated while others, often considered novelty pets, are not.

The popularity
of aquariums has been
slowly migrating from Europe and Asia to North America. New a
dvances in
low cost water filtration

offer easy maintenance for novice enthusiast.

Aquarium keeping is a popular hobby around the world. The predecessor of th
e modern aquarium
was introduced in 1850 as a novel curiosity; since then, aquarium ownership has expanded as more
sophisticated systems including lighting and filtration systems were developed to keep aquarium fish
healthy. (2)

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3.

M
ARKET ANALYSIS

3.1

Product De
finition

This device will dispense frozen fish food into an aquarium. It will be capable of dispensing frozen
blocks of food at a several times a day at any desired time (all times are programmable). The device
will use an array of thermoelectric coolers m
ounted onto a stainless steel cold plate to keep the
product frozen without making any noise. A heat sink is mounted onto the hot side of the
thermoelectric device. A low speed fan keeps the heat sink temperature low.

The insulating container will feature
a 14
-
turn rotating screw inside. The screw will accommodate 14
frozen blocks of food.

Design goals



∙Compact design capable of being mounted on top of a fish tank.



∙Easy cleaning, cube loading and maintenance



∙Device should be able to handle commercially a
vailable cubes of frozen food.



∙Easy to program with at least three pushbuttons to set the time of day and feed times.

3.2

Analysis of the pet products market

Figure 1:

Household breakdown by pet type

According to the American Pet
Product Manufacturers Association
(APP
MA), the U.S. pet products
market was worth 34.4 billion U.S.
dollars. 63% of U.S. households own
a pet, up from 56% of households in
1998 (3)

The number of households by pet
type can be seen in Figure 1. An
aquarist owns 10 to 12 fish on
average.(3)

Compa
red to dogs and cats, the
biggest advantages of fish are the low
cost of food, no expensive grooming,
and the low maintenance required (no
need to take the fish for walks like
dogs) (4).

U.S. Percentage of households by pet type
5%
32%
37%
4%
12%
1%
4%
5%
Bird
Cat
Dog
Equine
Freshwater Fish
Saltwater Fish
Reptile
Small Animal
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According t
o BusinessWeek, distribution of pet products is mainly d
one

through
small

retailers. Big
chain pet stores such as PetSmart (Petcetera in Canada) account for about 15% of total sales. Big
department store chains like Zellers and
Wal
-
Mart

also offer fish feed and some accessories. (5)

3.3

Competing products

There is
limited distribution of automatic feeders in Canada
; a
utomatic feeder selection is greater in
the U.S.
-

mostly dominated by dry food feed feeders. Prices for automatic dry food fish feeders vary
from US$14 up to $50 U.S. Note that all these products dispe
nse dry food.

Figure 2:

Automatic feeder types and prices (5)


Other products include live shrimp hatcheries from dry cysts


these hatcheries however are not
automatic feeders.

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4.

M
ECHANICAL
D
ESIGN

The most important component of the AFF is the thermoelectric cooli
ng device (TEC). The
arrangement and number of TECs will define the total power consumption and the overall cost
of the

Automatic fish feeder; Because of this, especial consideration is given to the design a operation
of
TECs

in the following section.

TEC

devices are available in packages that can be directly soldered to a surface or in a ceramic
sandwich style. TECs are semiconductor devices that provide cooling when current is passed though
them. They make use of the Peltier effect, which states that i
f a current is passed through a material,
a temperature differential will appear.


4.1

Thermoelectric cooling devices


Seebeck effect

When two wires that are made from dissimilar metals are joined at both ends are heated a current
begins to flow through the
circuit. In 1812 Thomas Seebeck was the first person known to have
made this discovery. The circuit can then be opened and a voltage can be measured at the terminals
called the Seebeck Voltage. This voltage is a function of the martial the two metals are
made from
and the temperature of the junction. Any two dissimilar metals will produce this result. If the
temperature difference is small the Seebeck voltage is linearly proportional to tempera
ture. The
resulting equation can be written as: ∆eAB = α∆T, where the Seebeck Coefficient “α” is the constant
of proportionality. (7)

Figure 3:

Seebeck Voltage diagram (7)


The Seebeck effect is what makes Thermoelectric cooling possible. The inverse of the Seebec
k effect
was discovered in 1834 by French watchmaker and physicist Jean Charles Athanase Peltier [3]
Peltier discovered that by applying a voltage to the Seebeck circuit a temperature difference is
created at the junctions. The result is a small heat pump
that has become known as a thermoelectric
cooler or Peltier cooler.

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©2005

4.2

Thermoelectric cooling system design

TECs manufactured today use many thermocouples in series. This arrangement allows meaningful
amounts of heat to be transferred from the cold side of
the device to a heat sink. Thermocouples are
most commonly constructed of the semiconductors Bismuth and Telluride, which are heavily doped
to create N
-
type or P
-
Type semiconductors; this means an excess of free electrons for N
-
type or lack
of free electr
ons (excess holes) for P
-
type. The two types of semiconductors are then connected
together and form a thermocouple. The resulting heat pump is able to cool devices below ambient
temperatures. (8)

Figure 4:

Thermocouples connected in series (10)


Figure 5:

Schematic of a the
rmocouple (9)




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Today’s conventional cooling systems are made up of 3 basic parts: A compressor, condenser and
evaporator. A pressurized refrigerant is allowed to expand and changes state from a liquid to a gas.
During this stage energy in the form of hea
t is absorbed and results in a temperature drop. The
compressor will then recompress the refrigerant. The heat generated by the compressor and absorbed
in the evaporator is now expelled in the condenser.

When comparing conventional cooling systems to TECs
several analogies can be made. Electrons at
the cold junction absorb heat as they move from the P
-
type (lower energy level) element to an N
-
type element (higher energy level). The electrons are moved through the system by the power supply
where the energy
is released into a heat sink as the electrons move from the N
-
type element back to
the P
-
type element. (8)

Thermoelectric devices have no moving parts, produce no noise, are rugged and very reliable.
Standard TECs are 40x40x4mm (length X width X height) or

smaller. The industry standard mean
time between failures is about 200,000 hours, which is more than 20 years for modules left in the
cooling mode. (11)

In order to choose a TEC three important specifications need to be stated. These are: The
temperatures

on the cold side, the temperature on the hot side and the amount of heat that must be
moved by the device.

The temperature difference across the TEC device is not the same as the measurable temperature
difference between the cold and hot sides of the syst
em. The methods of exchanging heat on the
cold or hot side of the system are an important consideration in order to achieve a desired result. The
efficiency of the heat exchanger depends on its unique characteristics. These represent a typical
value for
the heat sink operating temperature for the method used:



Finned forced air heat sink: 10 to 15°C above ambient air temperature



Free convection heat sink: 20 to 40°C above ambient air temperature



Liquid exchangers: 2 to 5°C above liquid temperature

T
he amount of heat to be moved by the device is called the heat load (QC). The load is comprised of
the amount of work needed complete the desired task; for example to cool an object or dehumidify
air. The load must also take into account the parasitic loa
d caused by losses to the surrounding
environment. Environmental losses are made up of loss through insulation, condensation of water,
formation of ice or conduction through wires. (8)

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4.3

TEC Calculations




Figure 6:

Parameters used in mathematical equations (12)


Table 1:

TEC Parameter Definitions

L = element height

R = electrical resistivity

Tc = cold
-
side temperature

N = number of couples

Qc = heat load

K = thermal conductivity

I =

applied current

V = voltage

A = cross
-
sectional area

S = Seebeck coefficient

Th = hot
-
side temperature




The basic equation for estimations on TEC performance:



V
T
T
L
A
K
A
L
R
I
T
I
S
N
Q
C
H
C
C




















2
2
1
2



(Equ: 1)

This can be simplified to:

















A
L
R
I
T
T
S
N
Q
C
H
C
2






(Equ: 2)

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©2005

4.4

TEC selection criteria

Because the actual differential equations are particularly unique for every system and have no
closed
-
form solution equations 1 and 2 are meant to only show the basic idea behind the
calculations. S, R and K are all temper
ature dependent and an assumption of constant properties can
result in large errors. (12)

To design a system using TECs manufacturing companies use powerful software to model the
complete system at the expected operating temperatures.(8) For the purposes o
f creating a prototype
a chart can be used to select a TEC that will operate in the desired range of expected temperatures.

For a small enclosed space to be effectively cooled in a temperature range typically found on earth
the Tellurex CZ1
-
1.4
-
127
-
1.14 w
as chosen. This device will easily operate from 20°C to 30°C for
our application. The Tellurex TEC is made up of 127 thermocouples and will pump 40 watts of heat
at 12 Volts with a current of 7 Amps. This should produce a 30°C temperature drop across the T
EC.
(13)

TEC manufactures provide a chart that helps in choosing an appropriate TEC. For the project
decisions for the operating voltage, current, temperature difference and heat moved were all made
from Figure 7. It is also possible to construct a simi
lar graph using equations 1 or 2.

Figure 7:

Performance of selected TEC (13)




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The Basic dimensions of the Tellurex TEC are 44x40x3.3mm (LxWxH) and pictured below.

Figure 8:

Tellurex TEC dimensions (13)



When choosing a TEC it is im
portant to consider the device performance vs. input power. The
diagram below shows the relation ship between the two. Input power can be, Voltage (V), Current
(I) or the product of the two, P=IV. The performance of the device can be stated as (Th
-
Tc), QC

or a
combination of these two parameters which is the case most of the time.


The terms ∆T
MAX

, Q
MAX

, I
MAX

or V
MAX

refer to the point where the curve peaks. Operating at or
close to the peak of this curve is inefficient and devices should be designed to

operate from 40% to
80% of maximum performance. (8)


Figure 9:

Diagram of performance vs. Input power (8)


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©2005

4.5

TEC cooling system design

The TEC cooling device used 4 TECs connected in a

series cascade. This arrangement allows one
TEC to be cooled by the TEC placed directly on top. The results of a series cascade are the lower
TEC will perform closer to the expected performance regardless of deficiencies in the attached
heatsink.

Figure 10:

TEC Coo
ling Overview


Figure 11:

Picture of TEC Assembly



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©2005

4.6

Housing and feeding system


The Design uses a coil to move the food to the dispensing hole. The food storage area is kept below
freezing by the TEC cooling device. In the front compartment the controlling electro
nics and LCD
display are housed. The housing has been constructed out of 11mm Plexiglas. The Plexiglas will
provide substantial insulation for the refrigerated area and is much easier to work with than metal.
For the prototype, the internal helical coil is

made of brass due to limited supply of stainless steel
rods. The coil on the final product will be made of stainless steel.

Figure 12 is a diagram showing the principal mechanical components of the Automatic fish feeder.

The Plexiglas feeder housing has
an opening on the base to dispense the food into the tank (the food
cubes fall into the tank). Two TECs are stacked together to obtain the required temperature
difference (
-
10°C) between the cold plate inside the feeder housing and the heat sink outside. 4

TEC
units are used in total (two sets of stacked TECs). The TECs are firmly attached to both the stainless
steel cold plate inside the tank and the heat sink to maximize the heat transfer and cooling efficiency
(nylon screws are used to secure the cold pl
ate to the heat sink). The gap between the cold plate and
heat sinks is sealed with foam to prevent condensation around the TECs. To avoid transferring heat
back to the cold plate nylon screws will be used to secure the cold plate to the heat sink. The ste
pper
motor is mounted into the housing using nylon screws as well. Silicone is used to seal off the gap
between the motor and Plexiglas isolating the inner chamber from the outside air. The lid of the cold
chamber is connected to the 12V power supply as re
quired by the TECs inside. A two
-
pins pressure
socket mounted over the Plexiglas unit will connect to the heat sink assembly allowing for easy
maintenance of the food area.

The solvent used to glue the Plexiglas effectively “welds” the Plexiglas together;
this is preferable to
drilling holes into the Plexiglas, which may weaken the material and cause cracks to form in this
area of higher mechanical stress.

The holes for the LCD display and buttons are cut from the front faceplate before it is welded. The
wa
ll between of the electrical compartment is insulated to prevent condensation and improve the
LCD operation. Adequate room was left to accommodate a thin layer of neoprene foam if needed.


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©2005

Figure 12:

Mechanical drawing



TOP VIEW

FRONT VIEW

Automatic Fish Feeder



Final Report

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Patrick Audet / Tomas Martin



©2005


Figure 13:

Automatic fish feeder housing and heatsi
nk assembly


Automatic Fish Feeder



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Patrick Audet / Tomas Martin



©2005


Figure 14:

Automatic fish feeder
-

fully assembled



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©2005

5.

E
LECTRICAL
D
ESIGN

The AFF is controlled by a programmable microcontroller; this is a necessity for a design that
features an alphanumeric LCD display that interacts with the user. The design requ
ires a stepper
motor to control screw forward/backward motion precisely

5.1

Component selection

5.1.1

LCD Display

The user interacts with the unit through a display/keyboard combination. A backlit LCD character
display will be used at it offers effective communicati
on of words at a minimal cost. An LCD works
like a light valve


Liquid crystals change light’s polarization angle when subject to a voltage
differential. Figure 15 shows the structure of an LCD display.

Figure 15:

Structure of a transmissive LCD display (16)


All
LCD character displays are sold as modules. The most common LCD controllers used in these
modules are the Hitachi HD44780 and the Samsung KS0066 controllers.

Figure 16:

HD44780
-
based 2x16 character display

The HD44780 controller is extensively
used in the industry
and features a 4
-
bit or
8
-
bit parallel interface. Documentation and
sample code is provided for all
microcontroller families. KS0066
-
based
controllers offer both parallel and serial
communications, however, LCD displays
based on this controller are not ver
y
common. Prices for HD44780
-
based
displays are lower and offer similar
performance to those based on the
KS0066.

The chosen module is a 16
-
character by 2
-
line, transmissive backlit LCD display.

1 Front glass substrate

2 Terminal

3 Segment electrode

4 Common electrode

5 Back glass substrate

6 Upper polarizer

7 Orientation layer

8 sealant

9 Liquid crystal

10 Conducting material

11 Sealant

12 Inlet

13 Viewing Area

14 Lower polarizing plate

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5.1.2

Microcontroller

Four types of Microcontrollers will be anal
yzed here. These microcontroller types were chosen due
to their low price, wide availability, and abundant support. All these microcontrollers are offered
with multiple built
-
in devices, memory types and sizes.

8051
-
based Microcontrollers

The 8051 is an 8
bit microcontroller originally developed by Intel in 1980. It is the world's most
popular microcontroller core, made by many independent manufacturers.

The 8051 is widely supported, with a a full range of free and commercial products available, its
archi
tecture matches control system problems (boolean logic). This microcontroller is also the one
that is offered at the lowest cost, with multiple options integrated into the same chip.

Due to its internal architecture, the 8051 is difficult to program in mac
hine language. Most of the
development products feature a C compiler. Development kits are priced from $50 to $100 U.S. (14)

PIC Microcontroller


The PIC microcontrollers were the first RISC microcontrollers. Although having few
instructions (e.g. 33

instructions for the 16C5X line versus over 90 for the Intel 8048), the PIC
line has a wealth of features included as part of the chip. The benefits of design simplicity are a very
small chip, small pin count, and very low power consumption.(15)

U
nusually for microcontrollers, the Microchip PIC data books include complete documentation on
how to program the chips
--

information that other manufacturers do not disclose easily. Parallax
offers PIC microcontrollers with a tokenized BASIC interpreter f
or fast development times

68xx series by Motorola

The popular 68hc11 is a powerful 8
-
bit data, 16
-
bit address microcontroller from Motorola (the sole
supplier) with an instruction set that is similar to the older 68xx parts (6801, 6805, 6809). The
68hc11
has a common memory architecture in which instructions, data, I/O, and timers all share the
same memory space.(15)

This microcontroller is widely used and extensively supported by Motorola. Machine programming
is much easier than the 8051nad PIC, and it c
an also be programmed in C.

The main characteristics of all microcontroller families can be seen in Table 2. From Table 2 we can
conclude that the Basic stamp module is excellent for fast prototyping, but it is unsuitable for mass
production due to its cos
t. Although Motorola’s microcontroller is easy to program and use, the
development costs are steep, it is single sourced and programming information is secret. The 8051
-
base microcontrollers and the PIC microcontrollers are used widely and are fully docume
nted with a
great number of free development tools


these two microcontrollers will be the most suitable for a
commercial low
-
scale project.


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©2005



Table 2:

Microcontroller characteristics (all prices in US$)


Device

Price

Ease of use

Comments

8051
-
Based (ATMEL)





Software programming tools

0.00

Medium

Freeware assembler and C compiler
available


Programming device


Easy

Included in Demo board


Demo Board

132.00

Easy

AT89STK
-
08 Starter Kit


MCU (chip only
-

mass product)

2.47


AT89C51
-
33PI
-
ND (40 pin DIP) 4
k Flash 32
I/O pins





Freescale MC68HCxx series





Software programming tools

499.00

Easy

Metrowerks Codewarrior "basic". Freescale
proprietary undisclosed


Programming device

30.00


None available for DIP MCUs


Demo Board

30.00

Easy

Lowest cost

programmer/demo board
-

includes SMT QFP MCU


MCU (chip only
-

mass product)

3.00


MC68HRC98JL3ECP (28
-
pin DIP)
MCU,128RAM,4K FLASH,A/D





Microchip PIC RISC MCU





Software programming tools

0.00

Medium

Freeware assembler and C compiler


Progra
mming device

199.00

Easy

Public programming info: Multiple
programming circuits available


Demo Board

99.00

Easy

Multiple sources, might not be needed


MCU (chip only
-

mass product)

1.65


SX28AC
-
DP+ (16 pin DIP) / other models
available





Parallax

PIC w/ BASIC





Software programming tools

0.00

Extremely easy

Freeware basic tokenizer


Programming device


Easy

Included in demo board/ same as PIC


Demo Board

50.00

Easy

BS2
-
SX OEM module


MCU (chip only
-

mass product)

12.00


SX28AC
-
DP+ (16 p
in DIP); No internal
memory for programs


EEPROM for MCU (required)

5.00


Required


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5.1.3

Stepper Motor

A stepper motor is required to perform precise screw movements (in degrees) as the screw must
move 360° exactly in each feeding operation. A stepper mot
or will also allow for forward/backward
motion to prevent the product from freezing into the screw and housing.

Stepper motors can be of two types: Permanent Magnet and Variable reluctance. Variable reluctance
motors run freely when no current is applied
while permanent magnet motors have a tendency to
show some resistance to movement. Permanent magnet steppers are heavier but easier to
manufacture; this explains their widespread use.


Unipolar motors

Figure 17:

Unipolar motor structure (17)

Unipolar stepping motors

can be controlled
using 6 wires and are usually wired as shown
in Figure 17, with a center tap on each of two
windings. The center taps of the windings are
typically wired to the positive supply, and the
two ends of each winding are alternately
grounded t
o reverse the direction of the field
provided by that winding


Bipolar Motors

Figure 18:

Bipolar motor structure (17)

Bipolar motors are constructed just like
unipolar motors, but the two windings are
replace with a single winding and the center
tap is eliminated. T
he motor itself is simpler
but the drive circuitry needed to reverse the
polarity of each pair of motor poles is more
complex (See Figure 18).


The drive circuitry for such a motor requires an H
-
bridge control circuit for each winding. An H
-
bridge allows
the polarity of the power applied to each end of each winding to be controlled in
dependently


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Other types of stepper motors
:

Bifilar Motors

Similar to the bipolar motor, but instead of winding each coil in the stator with a single wire, two
wires are wo
und in parallel with each other. Motors with bifilar windings are always powered as
either unipolar or bipolar motors.

Multiphase Motors

Multiphase motors are used in power/torque applications are very different from the unipolar/bipolar
construction as se
en in Figure 19.

Figure 19:

Bipolar motor structure (17)


Control of either one of these multiphase motors in either the Delta or Y configuration requires 1/2
of an H
-
bridge for each motor terminal. It is noteworthy that 5
-
phase motors have the potential of
deliveri
ng more torque from a given package size because all or all but one of the motor windings
are
energized

at every point in the drive cycle. Some 5
-
phase motors have high resolutions on the
order of 0.72 degrees per step (500 steps per revolution).

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5.1.4

Motor S
election
-

Bipolar stacked (1 W/coil)

The Bipolar motor was selected due to its easy construction, widespread use and low price. A
stacked bipolar motor was selected to allow for more even operation and greater angle control. A
stacked bipolar is just two b
ipolar stepper motors stacked together with a common rotation axis
allowing for standardization of parts and lower manufacturing costs. The selected motor electrical
schematic can be seen on Figure 20.


Figure 20:

Stacked stepper specifications (Danaher Motion)



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©2005

5.2

Power requirements

Table 3 shows the electrical power requirements for the AFF. TECs and Heatsink fans are connected
directly to the 12V power supply, as they have built

in control elements.


Table 3:

AFF Power requirements


ELEMENT

I

V

R

POWER

TEC

8.00

12.00

**

96.00

STEPPER

0.80

5.00

6.25

4.00

SOLENOID

1.00

12.00

**

12.00


S.T. POWER

4.30

**

**

46.00

LOGIC

0.30

5.00

N/A

1.50











TOTAL

4.60





159.50


5.3

Microcontroller selection

The Input/Output requirements for the microcontroller can be found in Ta
ble 4
:

Table 4:

TEC Input/Output requirements

Component

Pin requirements



Inputs

Outputs


Stepper

0

4

2
-
coil bipolar stacked stepper

Push buttons

3

0

Momentary contact type

LCD display

1

11

Hitachi
-
based; 7 outputs for 4
-
bit operation

Total

4

15

19 Total I/O
pins


The Basic Stamp 2SX OEM model was selected among the microcontrollers listed in Table 2. This is
due to the very limited amount of resources available to build a single prototype. The Basic Stamp
Module integrates a fully functional microcontroller
board with programming, debugging and
development tools for $50 US. The Basic Stamp does not have the required number of pins to
control all functions unless the LCD is operated in 4
-
bit parallel mode.

Figure 21 shows the schematic diagram for the BS2
-
SX m
odule.


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Patrick Audet / Tomas Martin



©2005

Figure 21:

BS2
-
SX Module schematic


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24

Patrick Audet / Tomas Martin



©2005

5.4

Electrical schematics

A block diagram of the electrical design is shown in Figure 22 and detailed electrical schematics on
Figure 23
.

Figure 22:

Automatic fish feeder


electrical block diagram

Basic Stamp 2 SX OEM
(Microcontroller module)
H

Bridge
I/O buffers
LCD Module
12 V DC Power supply
H

Bridge
Input switches
V. Reg.
TEC unit
TEC unit
TEC unit
TEC unit
Stacked stepper Motor
Fan
Fan
12V D.C.
5V D.C.
CONTROL
Feeding
mechanism
Basic Stamp 2 SX OEM
(Microcontroller module)
H

Bridge
I/O buffers
LCD Module
12 V DC Power supply
H

Bridge
Input switches
V. Reg.
TEC unit
TEC unit
TEC unit
TEC unit
Stacked stepper Motor
Fan
Fan
12V D.C.
5V D.C.
CONTROL
Feeding
mechanism

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Patrick Audet / Tomas Martin



©2005

Figure 23:

Electrical Schematic


Automatic Fish Feeder



Final Report

26

Patrick Audet / Tomas Martin



©2005

5.5

Software

T
he prototype system can deliver one frozen food blocks per day at a preprogrammed time. The
system runs a counter to derive a 1minute pulse which is used to run the real time clock (the clock
returns to zero at midnight). Feeding times are stored on a tabl
e (feed time table
-

FTT), which the
main loop checks constantly.

During normal operation (not during programming), the 2x24 LCD will display:

Standby


HH:MM

Software modules
:

5.5.1

Main module:

The main loop runs when the unit is
not being programmed or not dispensing food. The main
functions of the main loop are:



Maintains a counter that is used to estimate the time (loop counter)



Polls the buttons and enters programming loop if any of the buttons is pressed.



Displays the time on
the LCD display



Controls feeding events
-

enters the feed module when feeding time occurs

5.5.2

Set module:

The main module calls the programming module when the 'SET' button is pressed. This module is
the only module that interacts with the user. User programma
ble functions are:



Administers the FTT



Sets the time of day



Forced feed

The user interface is designed to use a 2x24 alphanumeric display and three buttons. The interface is
structured as hierarchical lists
-

the user navigates through the lists using the
'LEFT' and 'RIGHT'
buttons, and selecting options using the 'SET' button. The values are changed using the 'LEFT' and
'RIGHT' buttons. New values take effect by pressing 'SET' (which also returns the user to 'Stand by'
mode)

The following options can be se
t in programming mode:

TIME OF DAY:

Used to set the time, (in 24
-
hour format) that the unit uses to control feed times.


Internal clock mis estimated through a loop. During setup the LCD screen shows the following:

TIME OF DAY <> (set)

00:00 +hrs +mins

(set)

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Where 00:00 is the current time that the user adjusts using the “left” button for hours and “right
button for minutes. The user sets the time by pressing “set” once the right time is displayed on the
LCD screen. Once set, the unit will display the f
ollowing message for 1 second:


SETUP SUCCESSFUL


FEED TIME
: Allows the user to set the time of day at which the unit will feed one block of frozen
food. Further software improvements will permit multiple feed times per day. When setting feed
time th
e LCD display shows:

FEED TIME <> (set)

00:00 +hrs +mins (set)

The 00:00 text changes with the desired feed time. The user adjusts the feed time using the “left”
button for hours and “right button for minutes just as with time of day. The user sets th
e time by
pressing “set” once the right time is displayed on the LCD screen. Once set, the unit will the
following message for 1 second:


SETUP SUCCESSFUL


SET TEMPERATURE:

Will control the TEC current and therefore control the temperature. This
opti
on requires an analog input and thermistor. This function is not implemented in the current
design.

FEED NOW:

Will activate the feeding mechanism immediately, dispensing one block of frozen
food. The unit will display the following display while feeding:


** FEEDING **


EXIT SET MENU:

Returns to Standby mode. And waits for the next programmed feeding event.

5.5.3

Motor movement:

The motor movement modules move the motor for a single feed (360° rotation forward). The PLC
generates the signals that control

the two H
-
Bridges for the 2
-
unit
-
stacked stepper motor.

The complete source code can be found in Appendix A

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Final Report

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Patrick Audet / Tomas Martin



©2005

6.

P
RODUCT COSTS

6.1

Bill of Materials

The total cost of components required to assemble the prototype board can be found in Table 5
:


Table 5:


AFF Prototype


Material Costs

Part

Description

Amount

Unit Cost

Total Cost

ELECTRICAL






74LS05N

Hex Inverter

2

0.69

$1.38


2N6124

PNP

4

1.49

$5.96


2N6121

NPN

4

1.49

$5.96


108
-
4100

4x10 Breadboard

1

13.08

$13.08


--

Metal film resistor 10k

20

0.24

$4.80


--

Metal film resistor 1k

5

0.24

$1
.20


BS2SX

Basic Stamp B2SX OEM

1

62.50

$62.50


529PB
-
ND

Momentary SPDT

3

1.37

$4.11


LED

3mm LED

1

0.82

$0.82


1NS3xx

Diode 5W T18

8

1.55

$12.40


--

Wire. etc.

--

--

$10.00


SMT
-
75
2

Airpax stepper, 5V, 7.5deg

1

3.44

$3.44


LCD
-
107
2

2x24 Parallel LC
D w/EL

1

5.00

$5.00


MC78M05BT

500mA, 5V Regulator

1

0.89

$0.89


--

12V 3000RPM Fan

2

7.50

$15.00


PJT
-
2
2

Thermo Electric cooler

4

18.38

$73.50







MECHANICAL





--

Helical feeding screw



$0.00


--

Plexiglas Housing



$50.00


--

Heat sinks

2

4.
38

$8.75







TOTAL COST




$278.79


Prices per unit from Digikey Canada, AllElectronics.com
2


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©2005


6.2

Total costs and expected selling price

This is a unique product targeted at the enthusiast aquarist. There is no product in

the market capable
of automatically dispensing frozen food to an aquarium. This item should be sold as a novelty/luxury
item.

We believe the enthusiast aquarist will be willing to pay about $70 extra for the capability to handle
frozen food. A luxury auto
matic fish feeder with similar characteristics to the AFF (without freezing
capabilities) has a retail value of $65/US$50 (see Figure 2). Therefore, we believe the suggested
retail price (MSRP
) for this unit should be $13
0 as an absolute minimum.

I
f mass p
roduction of the AFF is achieved the cost reduction can typically be one fifth of the
prototype cost which is only $55.

With a MSRP of $130, a

profit of $75 per unit can not
actually
be
expected;

distribution

costs
,
packaging

and advertising costs will red
uce the over all profit

but not
too the extent that the AFF would be an unattractive business venture.


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©2005


7.

C
ONCLUSIONS




Fish and aquariums are the world's largest hobby. Aquarists spend much more money in
accessories and maintenance products than any other
type of pet owner. The profits from
aquarium related equipment exceeds that of any other pet type.



This is a novelty/luxury product that can be sold to enthusiasts for much a higher price than
current dry food automatic fish feeders. Manufacturing costs wi
ll have to be reduced to meet
suggested price target



The Automatic frozen food feeder depends on the availability of frozen food for fish. Current
availability is very limited.



8.

R
ECOMMENDATIONS




The total
cost should be reduced to $5
5
with mass production
. From Table
2, more than 50%
of the total cost is due to the TECs and BS2SX microcontroller.

Cost reductions should be
possible by targeting these areas.



Replace the BS2SX
-
OEM module ($75) with a single
-
chip microcontroller and integra
te this
chip into the circuit.
Th
ere are simpler microcontrollers av
ailable for less than $10US



More

efficient heat insulation on the feeding chamber to

allow

for smaller

more efficient

TECs.




Add a door to the food chamber to reduce cold air loss and reduce cooling requirements.



Add an e
xtra LED and a LED/photodiode detector pair to sound an alarm when the system
has run out of product.

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Final Report

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©2005


9.

R
EFERENCES

(1)

Hynes, Angela, Natural Health; Mar2005, Vol. 35 Issue 3, p72, 6p, 10c, 2bw

(2)


http://en.wikipedia.org/wiki/Pet

(3)

American pet product manufacturing Association (APPMA); Statistics page,
http://www.appma.org/press_industrytrends.asp

(4)

Alderman, Lesley; Money Magazine; Sep94
, Vol. 23 Issue 9, p154, 1/4p, 1c

(5)

Business Week; 9/23/2002 Issue 3800, p128, 1p, 1 graph, 3c

(6)

Petsmart;
http://www.petsmart.com

(fish


fish feeder section)

(7)

Omega, “Thermoelement Material
-
T30
-
Z”,
http://www.omegaeng.nl/temperature/z/pdf/z021
-
032.pdf

(8) Steinbrecher,
Tillmann; The Heat sink guide,
http://www.
heatsi
nk
guide.com/content.php?content=peltierinfo.shtml

(8)

http://www.melcor.com/handbook.html

(10)
http://www.digit
-
life.com/articles/peltierco
olers/

(11)
http://www.electracool.com/basics.htm

(12) TE Technology, Inc.;
http://www.tetech.com/techinfo/#1

(13) Tellurex Corporation;
http://www.tellurex.com/cz1
-
1.4
-
127
-
1.14cm.html

(14) Internet FAQ Archives; “8051 Microcontroller”,

www.faqs.org/faqs/microcontroller
-
fa
q/8051/

(15)

Internet FAQ Archives; “Microcontroller FAQs”,

http://www.faqs.org/faqs/microcontroller
-
faq/primer/

(16)
http://www.displaytech
-
us.com/pdf/ol_lcd/LCDConstruction.PDF

(17) Douglas, Jones (Ph.D.); “Control of Stepping Motors

(18) “
A Tutorial”,
http://www.cs.uiowa.edu/~jones/step/types.htm
l



APPENDIX A


Automatic Fish Feeder



Final Report


A
-
1

Patrick Audet / Tomas Martin



©2005

APPENDIX

A


AFF Software for BSX2
-
OEM



' {$STAMP BS2sx}

' {$PBASIC 2.5}


#SELECT $STAMP


#CASE BS2


#ERROR "BS2e or greater required."


#CASE BS2E, BS2SX


Slot CON 63


#CASE BS2P, BS2PE, BS2PX


Slot CON 127

#ENDSEL
ECT


' defines variables to use in the program

lcdchar VAR Byte ' character to be output by the LCD routine

lcd_low VAR lcdchar.LOWNIB ' break up byte for 4 bit lcd interface

lcd_hi VAR lcdchar.HIGHNIB ' break up byte for 4 bit lcd interface

idx VAR Byte
' counter for printout looping

hours VAR Byte ' hours
-

time (main loop)

mins VAR Byte ' counts minutes to keep time (main loop)

fd_hours VAR Byte ' feed time hours

fd_mins VAR Byte ' ' feed time minutes

secs VAR Byte ' seconds
-

time (main loop)

tmp VAR
Byte ' temprary storage for calculations

setstate VAR Byte ' current state that we are setting


' I/O definitions

' Three push buttons ( IN )


sw1 VAR IN0


sw2 VAR IN1


sw3 VAR IN2

' Motor Control


mtout VAR OUTB

' LCD control lines


L_ENA VAR OUT13



L_RS VAR OUT14


L_NIBOUT VAR OUTC ' Nibble for out8
-
out11


L_RW VAR OUT12

' constants


debounce CON 200 ' 200 ms debounce


stpdly CON 30 ' delay between steps

APPENDIX A


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-
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Patrick Audet / Tomas Martin



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stp1 CON %1001 ' stepper motor h
-
bridge combinations


stp2 CON %0101


stp3 CON
%0110


stp4 CON %1010


moff CON %1111 ' turn motor off

Init: ' Resets Direction registers, motor outputs to 1 (i.e. 0)


' program the IO direction register to our needs

' input=0 output=1

' 5432109876543210

DIRS = %1111111111111000

'
---
RDDDD
REMotSwt


' resets outputs (inverter buffers on motor transistors)

' 5432109876543210

OUTS = %0000000000111000 ' motor output low

'
---
RDDDDREMotSwt


'init motor

GOSUB fwd


' initialize LCD display

PAUSE 1000

L_RS=%0

L_RW=%0

L_ENA=%0

L_NIBOUT=%
0011

GOSUB lcdout '1

PAUSE 6 ' wait for more than 4.1ms

L_NIBOUT=%0011

GOSUB lcdout '2

PAUSE 1 ' wait for more than 100us

L_NIBOUT=%0011

GOSUB lcdout '3

L_NIBOUT=%0010 ' last init nibble this is a 8
-
bit instruction

GOSUB lcdout '4

L_NIBOUT=%0010 ' 0
01x:0= 4bit interface

GOSUB lcdout '5a

L_NIBOUT=%1000 ' N=1(2 lines) F=0 (5x8dots)

GOSUB lcdout '5b

L_NIBOUT=%0000 ' Display on

GOSUB lcdout '6a

L_NIBOUT=%1111 ' 1DCB display, cursor and blink on=1/off=0

GOSUB lcdout '6b

L_NIBOUT=%0000 ' Display clear

GOSU
B lcdout '7a

L_NIBOUT=%0001 ' =0001

GOSUB lcdout '7b

L_NIBOUT=%0000 ' Entry mode set

GOSUB lcdout '8a

APPENDIX A


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L_NIBOUT=%0110 ' 0 1 I/D S cursor behaviour and shifting

GOSUB lcdout '8b

L_RS=%1 ' we are assuming printing all times, no commands


lcdchar=0 ' prints we
lcome message

GOSUB setpos

idx=welcm_msg

GOSUB prt_str


PAUSE 1000 ' waits for 5 seconds and goes to standby


stdby:


lcdchar=0 ' prints standby


GOSUB setpos


idx=standby


GOSUB prt_str


stdbyloop:


GOSUB printtim ' prints time on second line


' de
tect buttons


FOR secs = 0 TO 5 ' seconds


PAUSE 980 ' 980ms delay


IF (sw1 | sw2 | sw3) THEN GOTO uiset 'jumps to setup ui if pressed


NEXT


' update clock


mins=mins+1


IF mins>59 THEN


hours=hours+1


mins=0


ENDIF


IF hours>23 THEN hou
rs=0


' checks feed time


IF ((fd_hours=hours) & (fd_mins=mins)) THEN


GOSUB feednow


GOTO stdby


ENDIF



GOTO stdbyloop ' branches back


'****************************************

'*** UISET user interface to set opts ***

'************************
****************


uiset:


setstate=0 'Option currently being set up = 0


topuiloop:


GOSUB clrs

APPENDIX A


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Final Report


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-
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LOOKUP setstate,[set_feed, set_time, set_temp, set_feednow, set_end],idx


GOSUB setpos


GOSUB prt_str ' print message for setstate


PAUSE debounce


lup1
:


IF (sw1 | sw2 | sw3)=0 THEN GOTO lup1


setstate=(setstate
-
sw1+sw2)


IF setstate>4 THEN setstate=0


lcdchar=0 ' adjusts position of message


IF sw3=0 THEN GOTO topuiloop 'loops ntil set pressed


IF setstate=4 THEN GOTO stdby ' EXITS TO STANDBY LOOP


IF setstate=3 THEN GOSUB feednow ' feeds the


IF setstate=3 THEN GOTO uiset



IF setstate=0 THEN 'set feed


hours=fd_hours


mins=fd_mins


ENDIF



' sets option (= sets time)


lcdchar=64 ' button operation txt on 2nd line


GOSUB setpos


idx
= set_tim_msg


GOSUB prt_str

set_tim_opt:


GOSUB printtim ' prints time to be set


PAUSE debounce

lup2:


IF (sw1 | sw2 | sw3)=0 THEN GOTO lup2


mins=mins+sw2


IF mins>59 THEN


hours=hours+1


mins=0


ENDIF


hours=hours+sw1


IF hours>23 THEN



hours=0


ENDIF


IF sw3=0 THEN GOTO set_tim_opt 'loops until set pressed



IF setstate=0 THEN


fd_hours=hours


fd_mins=mins


ENDIF



GOSUB clrs


idx= setsuccess


GOSUB prt_str ' print message for setstate


PAUSE 1000


GOTO uiset

APPENDIX A


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Final Report


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-
5

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©2005


'********
********************************

'*** Useful routines ***

'****************************************


feednow: ' prints message and rotates forward 360


GOSUB clrs


idx= feeding


GOSUB prt_str


GOSUB fwd

RETURN


printtim: ' prints the
time (from hours:mins)


lcdchar=64 ' sets position second line


GOSUB setpos


tmp=(hours/10) ' form ascii char (hours 1st digit)


lcdchar=tmp+48


GOSUB prt_char


tmp=(hours
-
(tmp*10))' form ascii char (hours 2nd digit)


lcdchar=tmp+48


GOSUB prt_cha
r


lcdchar=%00111010 ' colon


GOSUB prt_char


tmp=(mins/10) ' form ascii char (hours 1st digit)


lcdchar=tmp+48


GOSUB prt_char


tmp=(mins
-
(tmp*10)) ' form ascii char (hours 2nd digit)


lcdchar=tmp+48


GOSUB prt_char

RETURN


clrs: 'clears the LC
D screen


lcdchar=%00000001 'clears the screen


L_RS=%0 ' command


GOSUB prt_char


lcdchar=%00000000 'position zero


GOSUB setpos

RETURN


prt_str: 'prints a zero
-
terminated string on the LCD located at idx


READ idx, lcdchar


idx=idx+1


IF lcdchar=
0 THEN RETURN


L_NIBOUT= lcd_hi


GOSUB lcdout


L_NIBOUT= lcd_low


GOSUB lcdout

GOTO prt_str


prt_char: 'outputs a byte to the LCD

APPENDIX A


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Final Report


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-
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©2005


L_NIBOUT= lcd_hi


GOSUB lcdout


L_NIBOUT= lcd_low


GOSUB lcdout

RETURN


lcdout: '4bit transfer to lcd routi
ne


PAUSE 1


L_ENA=%1


PAUSE 1


L_ENA=%0

RETURN


setpos: ' sets the position of the next character to be printed LCD


L_RS=%0 ' Changes mode to command


L_NIBOUT= %0000 ' return home


GOSUB lcdout


L_NIBOUT= %0010


GOSUB lcdout


' move to

desired pos


L_NIBOUT= (lcd_hi | 8)


GOSUB lcdout


L_NIBOUT= lcd_low


GOSUB lcdout


L_RS=%1 ' And back to data

RETURN


fwd: 'moves the motor 360deg fwd (feeding motion)

FOR tmp=0 TO 12


mtout= stp1


PAUSE stpdly


mtout= stp2


PAUSE stpdly


mtou
t= stp3


PAUSE stpdly


mtout= stp4


PAUSE stpdly

NEXT


mtout= moff ' turns off current to coils

RETURN


'Messages

' 1 2

' 123456789012345678901234

welcm_msg DATA " ** GUPPY LUV **",0

standby

DATA "STANDBY
-

(Press to set)",0

set_time DATA "TIME OF DAY <> (set)",0

set_feed DATA "FEED TIME <> (set)",0

set_temp DATA "SET TEMPERATURE <> (set)",0

set_feednow DATA "FEED NOW ",0

APPENDIX A


Automatic Fish Feeder



Final Report


A
-
7

Patrick Audet / Tomas Martin



©2005

set_end DATA "Exit set menu

",0

set_tim_msg DATA " +hrs +mins (set)",0

setsuccess DATA " SETUP SUCCESSFUL ",0

feeding DATA " ** FEEDING ** ",0