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Context and Objectives.
The system I am going to study is the
current environment cold blooded
reptiles are kept in as pets within
today's society, and how this effects
their health. I am already aware of a
few flaws in this system, due to the
systems being fully open systems
allowing for errors in user inputs.
I believe that there is a lack of both knowledge and systems for the specific
conditions that a reptile will require in order to live healthily. The combination
of both these lacks can cause pet reptiles to suffer, causing unknown animal
cruelty. If the systems could be improved to a specific level, then it would allow
for the ignorance of pet owners and still cause the reptiles no further suffering.
This is why I am studying this system, as a personal pet owner, and the keeper
of an okeetee morphed corn snake I am aware of the difficulties of keeping it
healthy with the current system.
During my study I will need to investigate and gain more knowledge on the
designing of a system to improve the living conditions of reptilian pets. Some of
the design factors necessary to achieve this are:
The use of CAM and CAD in the designing of the system, to enhance the
overall system by making accurate calculations and/or design ideas.
The consumer needs at present time and in the predictable future, meeting
these needs, such as easy use of the system to keep the reptiles healthy, will
allow for a more specific and appropriate system rather than a system that
does hundreds of unrequited operations.
The electronic systems required in the system to ensure everything works as
it should in the vivarium, ensuring the health of reptilian pets.
The analysis of existing products to ensure there are not any systems exactly
the same as the improvement I will induce. I can also retain ideas from existing
products (while considering copyright laws) to help enhance the system.
The cost of my product is in need of deep investigation as I am already aware
that vivariums are extremely expensive on their own, let alone with a system
attached, although they are not relatively expensive to manufacture.
The materials used in the systems will require good aesthetics and some
ergonomics on a possible controller. Also there are certain materials used in the
heat mats on the vivarium floor.
Reptiles are extremely susceptible to their current environment, if this is
inefficient in any way, the reptile can become unhealthy, thus the maintenance
of the specific environment must be maintained or the reptile will become
unhealthy, or even in more serious cases die.
The operational costs of the system is in need of investigation also, because if
the amount of power wastage can be reduced, then the costs of running the
system are also reduced.
The Quality to Cost ratio will also need to be addressed as good quality
equipment is expensive and will raise the prices of the system, finding a balance
between both price and quality is the best solution to consumer needs.
There is also an amount of manufacturing issues that need investigation for this
system these are:
The interpolation of the entire system, how everything fits together and why,
ensuring that nothing will break too easily, and what will go where and stay rather
than move unexpectedly, while bearing in mind there will be a living moving creature
inside, that might effect the entire interpolation of the system.
The materials used in manufacture will also be investigated to show how the
strength, aesthetics and ergonomics of the system whilst being able to maintain a
specific environment.
Health and safety issues will also need to be revised as the system must adhere to
ALL of the laws regarding health and safety otherwise the system will be dangerous
to use.
The schools manufacturing limits will also require investigation as if it does not have
the specific equipment for a job, I cannot use that part of the system, and may have
to alter the entire system accordingly.
I will also require investigation into the universal design tools used in the
manufacture of this system, like what CAM software will I require to use the cutters
available.
The preparation of the manufacture will also require a decent amount of attention,
what tools are required, what electronic components need to be purchased ect.
The assembly of sub systems within the system is of great importance and will
require a lot of research, if all the sub systems do not work as a whole, the system
will not function adequately, causing suffering to the reptile.
The readiness of the product to be converted into something that is batch
producible is in need of research because at present the system will be a one off
product, and if the system is to enter the market it will need to be available by batch
production.
The time of manufacturing will require a great deal of attention as I only have a set
time limit in which to investigate, design, manufacture, test and evaluate, therefore I
will have to be able to utilize all the time I have to the highest possible standard.
The energy costs of manufacturing will need to be advised as if the manufacturing
energy costs are high it will be both a danger to the environment and a less cost
effective system.
From this I hope to gain:
Knowledge on how systems interpolate.
The ability to manage not only my time but also different materials and circuits.
A fully functioning system that will increase the quality of pet reptilian living
conditions,
Information about controlling systems and how they function for use in further life.
Knowledge on mass production techniques, so I can use the knowledge in later life
to aid in the job areas I am looking in.
From this I hope the reader will gain:
Enjoyment from reading this investigation and learning about the system.
A gain of enthusiasm about both the system and reptilian needs.
In depth knowledge about the requirements of reptiles, and the system itself.
A realisation of how reptile pets are more demanding than most people realise.
A gain of interest about reptilian pets
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Plan of Action.
Hours.
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9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
Plan of action and clarification of problem.
- analysis of the product.
- production of a brief.
- conduction of research.
- analysis of research data.
- production of the specifications
Development of design proposals.
- production of a range of ideas.
- analysis of ideas to work up a proposal.
- working up the proposal into a viable solution
- production of a manufacture plan.
Manufacturing and modelling.
- ordering and collecting materials.
- completion of sub systems.
- assembly and testing.
Conclusions, evaluations and recommendations.
- designing testing procedure.
- gaining user analysis.
- writing up findings.
Communication and presentation.
Ghant chart.
For my plan of action I have decided to use a Ghant chart to plan out the time distribution., this will allow me to plan my allotted time (100 hours) into all sections of work . I have split the time (100 hours) into 5 main sections:
Plan of action and clarification of problem, Development of design proposals, Manufacturing and modelling, Conclusions evaluations and recommendations and finally communication and presentation. These 5 main sections
cover all of the time given and are indicated by purple lines on the Ghant chart. The main sections are split into numerous sub-sections showing what I will be doing in this time and when I will be doing it in that time area, the
subsection timings are shown by a blue line on the chart. I am aware that in a project certain circumstances arise that cannot be avoided and waste time, for this I have allowed for an overflow limit on each section to cover if
this circumstances do arise, this is shown by a red marker on the Ghant chart. The lines overlap at the overflow limits as they can be started then if the other tasks are completed in time. The final main section
(communication and presentation) covers all of the Ghant chart as I will be continuously working on this task throughout all my project, it also has a time slot at the end to allow for improvement of the whole project.
Communication and presentation is also the only main section not to consist of sub-sections as these are trivial and not required within this section.
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Research Plan.
This Spider diagram is a basic plan of
research, I have indicated my main focuses
of research (red ovals) and what I will need
to research about them (black squares).
This diagram is shown in a tabulated
format, with the information on how and
why I will do this research, on the page
below.
Safety.
Humidity.
Cost.
Temperature.
Demands.
Animal
Requirements.
Commercial
Viability.
Materials.
Humidity
controllers.
Vivarium
Types.
Specific
Condition
Vivariums.
Possible areas
of Research?
Technology
Required.
Size.
Already on
market?
Temperature
controllers.
Existing
Products.
Temperature
measurers.
Materials
Required.
Price?
Woods.
Availability?
Humidity
measurers.
Size?
Metals.
Composites.
Plastics.
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Research Plan.
What?
Why?
How?
Commercial viability.
To see if, and why the product will sell on the market.
Questionnaires of reptile owners (sample of 20).
The Cost of the finished product.
To find out how much the consumers are willing to pay for the product.
Questionnaires of reptile owners (sample of 20).
The consumers needs and wants.
To find out what the product will require.
Questionnaires of reptile owners (sample of 20).
Technologies.
To gain knowledge of technologies that may be of use in the product.
Various methods.
Humidifiers/De-humidifiers.
To find ways of controlling the humidity within the vivarium.
Expert Advice, internet research.
Temperature Control.
To find a suitable way of controlling the temperate to the set requirement.
Use of internet engineering sites.
Temperature Recording.
To find a suitable way to measure the temperature of the vivarium.
Use of internet engineering sites.
Humidity Recording.
To find a suitable way of measuring the humidity of the vivarium.
Use of internet engineering sites.
Materials.
To find suitable materials for the my product.
Various methods.
Metals.
To find if there are any suitable metals I can use in my product.
Testing metals, internet research.
Plastics
To find if there are any suitable plastics I can use in my product.
Testing plastics, internet research.
Woods.
To find if there is any suitable timber I can use in my product.
Testing wood, internet research.
Composites.
To find if there are any suitable composites I can use in my product.
Testing composites, internet research.
Existing Products.
To gain information on competition in the market, or a respective gap.
Checking in-store, internet research.
Any already on the market?
To see competition or gaps for my product.
Checking in-store, internet research.
Price of those on the market, or similar products.
To gain a respectable price range for my product.
Checking in-store, internet research.
Availability of the products.
To find if there is a real need for my product
Checking in-store, internet research.
Size of the products.
To see if my product can be smaller than existing products whilst still
functioning.
Checking in-store, internet research.
Types of vivarium.
to gain specific information as to whether my product is best suited to one type
of vivarium.
Personal knowledge, expert advice, internet research.
Size.
To gain appropriate info on size vs. heating strength ratio.
Personal knowledge, expert advice, internet research.
Materials.
To gain relevant information on he materials best suited to a vivarium.
Personal knowledge, expert advice, internet research.
Specific condition vivariums.
To see if my system is better in a specific condition vivarium e.g.: watertight.
Personal knowledge, expert advice, internet research
Animal Requirements.
To ensure the system will meet the animals health requirements.
Personal knowledge, expert advice.
Temperature.
To ensure the animal will not overheat/freeze.
Personal knowledge, expert advice.
Humidity.
To ensure the animal will not drown/dry out.
Personal knowledge, expert advice.
Safety.
To ensure my product cannot harm the animal.
Personal knowledge, expert advice.
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Research area 1 - Commercial Viability.
Primary research.
For my primary research into the commercial viability I have chosen to ask 20 people who own reptilian pets, or are interested in reptilian pet safety what they want/need in a possible system, this questionnaire is shown in the
appendices. I decided to use a liket scale as it provides a rapid and easy to understand set of quantitative data, this data will allow me to see where consumers want specific things or if they would prefer not to have them, by
calculating the total score (multiplying the amount of people choosing a score (eg 3 people choosing four gives a total of 12), then adding all the scores for the question together and then dividing by the total amount of people
asked (20). This will give me the average score for each question, I have decided that if the average score is above (or very close to) 3.5 then I will incorporate that idea into my project as a specification, if this is possible. The
reason for choosing 3.5 is it is above halfway and will indicate a majority view on the subject.
Results.
The results below show that the potential consumers would prefer a self heating vivarium (average point score=4.15) and a majority would also like one that maintains humidity also. There seems to be a common
thought as to the knowledge of reptilian pet safety is low, indicating the need for a self maintaining system to overcome human ignorance. The majority of potential consumers would prefer a separate attachment to a
vivarium, so this will be the design base of my product if it is at all possible. This information will be what I base the most simple design of my product around, ensuring I meet all the criteria given by the results where
possible (self heating, humidity controlling, separate from vivarium). By following these criteria I can ensure
1
2
3
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Average
score.
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a self heating vivarium?
1
3
0
4
12
4.15
a humidity controlling vivarium?
2
5
1
6
6
3.45
17
2
0
0
1
1.30
Fixed into a vivarium?
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3
2
2
4
2.45
Separate add on?
4
3
2
2
9
3.45
price.
4
8
6
1
1
2.35
the widespread knowledge of reptilian pet requirements?
Conclusions.
From this set of results I can conclude that the consumers are almost all wanting a self heating vivarium, so I will have to include this as a specification into my product due to the sheer demand. While only scoring 3.45,
the humidity control is very near the limit, and with my own personal knowledge I will include it in my product as there is a definitive lack of information known to the general public (shown by the small score of 1.30) so in
order to fill this gap my product must cover all the reptilian requirements to ensure no animal cruelty is caused by ignorance. My product is probably going to be a separate add-on due to the higher demand of that to the
fixed idea, even if it does fall short of my score limit, the product must be one of the 2 so I will go with the most popular answer. The consumers do not seem too influenced by the price of the product showing a
preference of quality over prices, understandable within the circumstances, this means that I can use more expensive materials (when available) within my product to ensure it works efficiently. With these specifications I
can now define the key areas where I will have to provide extra research on, these areas are :
•Temporary fixing methods
•Components – price, reliability and tolerance.
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Research area 2 - Required Technologies.
Humidity measurement.
I found 2 main techniques to measure the
humidity of the vivarium, one is a
psychrometers using a wet and a dry bulb,
the other is a mechanical system using
organic matter.
Wet and dry bulb psychrometers are the most
simple and common way of measuring
humidity. This type of hygrometer uses two
basis thermometers, one
with a wet bulb one
with a dry bulb.
Evaporation from the
water on the wet bulb
causes its
temperature reading
to drop, causing it to
show a lower
temperature than the
dry bulb.
Relative humidity is
calculated by
comparing the readings using a
calculation table (shown on next page) that
compares the ambient temperature (the
temperature given by the dry bulb) to the
difference in temperatures between the two
thermometers.
A mechanical
hygrometer uses
a slightly more
complex system,
based on one of
the first
Hygrometers
designed in 1783
by Horace Bénédict de Saussure. This
system uses an organic material that
expands and contracts as a result of the
surrounding humidity. The organic material is
held under slight tension by a spring, which is
linked to a needle gauge that indicates the
level of humidity based on how the hair has
moved.
The best method to measure humidity will be
with the psychrometers as I can use
thermistors in a potential divider to measure
the change in humidity via temperature.
Humidity control.
Increase.
Steam – Often
referred to as a
"vaporizer," a
steam humidifier
boils water and
releases the warm
steam into the
Air. This is the
simplest, and
therefore the least expensive, technology for
adding moisture to the air
Impeller - In this humidifier, a rotating disc
flings water at a comb-like diffuser. The
diffuser breaks the water into fine droplets
that float into the air. These droplets are
usually seen as a cool fog exiting the
humidifier.
Ultrasonic - An ultrasonic humidifier uses a
metal diaphragm vibrating at an ultrasonic
frequency, much like the element in a highfrequency speaker, to create water droplets.
An ultrasonic humidifier is usually silent, and
also produces a cool fog
Decrease.
The four main ways to decrease humidity are
to:
1-Increase heating temperature
2-Increase minimum pipe temperature
3-Reducing the venting temperature
4-Set a minimum vent opening
The first 2 options are ineffective on their
own, and can even be counterproductive due
to the water evaporating in the heat, the third
option is highly effective as it condenses
water in the air before it enters the vivarium
reducing humidity, however it can also have
a counter effect of cooling down the vivarium
itself.
Setting a minimum vent opening will allow for
cooler dry air to be added when needed and
not when the air is dry but too cold, a mixture
of the last two ideas is probably the best for
my circuit as there is always a pool of water
in a reptile vivarium and it will also require no
method of increasing humidity as with the
temperature requirements in a vivarium water
evaporation will occur naturally.
Temperature measurement.
I had previous knowledge of the first three
options to measure temperature however
after researching I compiled information on
thermocouples also.
Thermistors.
Allow for direct input of the relative
temperature into a circuit via a change in
resistance, when used in a potential divider
they can compare the temperature to a set
amount (given by another resistor) before a
signal is produced, causing a limit on the
maximum/minimum temperature. Also if the
second resistor is variable, the temperature
limits can be changed.
Limit switch on a thermometer.
Applying two limit switches to a thermometer
with a mechanical dial will allow for a
permanent temperature limit to be reached,
however as this cannot be changed it will
only ever be suited for one type of reptile as
they all have different requirements.
Separate thermometers.
A separate thermometer will allow the owner
to see the temperature at the current setting
and higher/lower the temperature output in
accordance, however this makes the product
an open system instead of a mainly closed
system as it will require regular attention
(every few days).
Thermocouples.
A junction between two dissimilar metals
produces a voltage. In the thermocouple, the
sensing junction produces a voltage that
depends upon the temperature. This voltage
can then be read by a circuit (eg: a
programmable interface controller (PIC)) in
order to display the temperature or to perform
an action at the limit voltage.
The best solution to my product is the
thermistors as they are small, inexpensive
and are easily integrated into the circuit, they
also allow for an alteration in the limits of the
temperature to allow for the different animal
requirements.
Temperature control.
Heating.
I could only find two methods of generating heat energy
electronically, these method are known as Joule heating
and friction conversion.
Joule heating, also known as ohmic heating and resistive
heating, is the process by which the passage of an electric
current through a conductor releases heat. By varying the
current and the length of the wire the heat produced varies
in proportion to the square of the current multiplied by the
electrical resistance of the wire. This will allow for the
heating of the vivarium using strips of metal, however these
will have to be covered as the metal will reach a high
temperature and would harm the reptile. The conversion of
friction into heat could be made by having two rotating
objects moving at a reasonable speed against each other,
this will convert some energy into heat which can then be
supplied into the vivarium, however this is a highly
inefficient system and would require more venting, so the
best option of increasing the temperature is to induce joule
heating.
Conserving.
A way to keep the temperature at an intended level for a
longer period of time would be to conserve the heat already
in the vivarium, this is usually very energy efficient and
could be achieved by using insulating foam in the walls of a
vivarium this however stops heat entering the vivarium via
the walls and will not cover glass panels, or by using “solar
glass” which allows heat to enter the vivarium but not
escape, this could however overheat the vivarium if not
constantly attended to. The main disadvantage of both of
these is that they would require a full vivarium to be
manufactured and altered, making my product large and
expensive, these will have to be taken into further
consideration with the consumer ideals.
Cooling.
I found two ways of cooling down the vivarium. The first
method of cooling is to just let it cool itself down, this can
take time to occur but allows for a gradual decrease of heat
with no energy output at all. The other method is to use the
Peltier effect when a current is passed through a specific
circuit the upper junction of the circuit releases heat (could
be used for a heating system) while the lower junction
absorbs heat (used for cooling system) however this circuit
is complex and requires the use of specific and expensive
materials beyond my productivity limits.
7
Research area 2 - Calculation Table.
WET BULB TEMPERATURE
61
62
63
64
65
of
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
3
7
11
15
19
23
27
31
36
40
44
49
54
58
63
68
73
78
84
89
94
100
1
4
8
12
16
20
24
28
32
37
41
45
50
54
59
64
69
74
79
84
89
95
100
2
6
10
14
17
21
25
29
33
38
42
46
51
55
60
64
69
74
79
84
89
95
100
1
4
8
11
15
19
23
26
30
34
39
43
47
51
56
60
65
70
74
79
84
89
95
2
6
9
13
16
20
24
28
31
35
39
44
48
52
56
61
65
70
75
80
85
90
2
4
7
10
12
15
18
21
24
27
31
34
37
40
44
47
51
2
4
6
9
11
13
16
18
21
23
26
29
31
75
DRY BULB
83
TEMPERATURE
oF
This table is used to calculate the relative humidity from the psychrometer readings (previous page) at the shown temperatures (of) on both the wet and dry bulb a reading is shown
for the relative humidity. For example when the temperature is 61oF(16oC) in the vivarium and 50oF(10oC) in the water the relative humidity is 49% at some temperatures
(eg:40oFin the wet bulb and 65oF there is no reading, this is because there is no relative humidity in these temperatures due to the fact that unless in a false condition the water
should never reach lower than 41oF)
8
Research area 3 - Existing Products.
Helix DBS-1000 Proportional Thermostat
The best digital proportional thermostat on the market!

$129.95 each
You save $5.00
Helix DBS1000 Thermostat with grounded plug
Same features as original DBS1000, but comes with a grounded plug for use with metal rack systems.

$136.00 each
You save $3.95
Helix DBS 1000 Thermostat & Temp Gun Special
Helix DBS 1000 Thermostat & Infrared Temperature Gun

$149.99 each
You save $5.00
Helix DBS1000, Night Drop Cord & Temp Gun Combo
Special includes the DBS1000 Helix Thermostat, the Appliance Timer Adapter Cord and the $25 Infrared Temperature Gun

$174.99 each
http://lllreptile.com/store/catalog/reptile-supplies/thermometers-thermostats-and-timers/
Conclusions.
After Conducting some research I found these products that are similar to what mine will be, however they all only measure and control temperature (albeit accurately) and are extremely expensive and cost
around the same price as a vivarium itself, even with the discounts. This means my product will have a good standing on the market, however as there are so few products like this it shows that the market niche is
very small and I should be careful to make sure my product meets consumer demand, or it may not become successful. However the size of these products is very small and my product will have to be a lot larger
in order to cope with the humidity, I believe though that the requirement for a set humidity will outshine the want for a small product. These products are small add-ons to a vivarium that both measure and alter the
temperature within a vivarium, in this respect they are almost the same as my system, however they do not monitor humidity in any aspect which I am hoping for my product to do. However these products are from
a reputable brand of thermostats and so consumers might look over my product at a lower price due to their reputation.
Other products for the sub-systems.
I have realised that to find alternate methods of controlling the humidity and temperature of my design it is possible to look at existing products for inspiration.
Existing products to alter environments.
- Fish tank heaters increase the temperature of the specific environment they are in quickly and are easy to attach, the main problem with using a fish tank heater is that my vivarium is not underwater and if a fish
tank heater is turned on out of water they will crack and stop functioning. This problem is easily solved by encasing the heater within a water tight casing filled with water, this will allow the heat to travel by
convection out of the water into the water and into the vivarium. This product can be used for both temperature and humidity if placed in a specified water bath.
-- Radiators increase the temperature in a house by moving hot water through the system, while moving hot water is not viable for my design, using still hot water being heated in copper tubes is viable and will
give a similar effect. The convection of the heat will also supply a temperature gradient that reptiles require.
-Greenhouses alter the temperature and humidity by opening and closing windows automatically, while an open window would be a hazard for a reptile escaping, fixing a mesh into the window would prevent the
reptile escaping, however a moving object in a vivarium is not viable due to predatory reptiles thinking it is prey and/or a threat.
- bi-metallic strips are used in greenhouses also, they detect larger fluctuations in temperature and bend accordingly, this being is caused by the two metals it is composed of having different rates of expansion
and compression.
-Misting mechanisms extrude a mist of water into the environment greatly increasing the humidity, they however cool down the environment which is not a good thing for the reptile within the vivarium. These
mechanisms use solenoid valves to separate the water into a mist these mechanisms also require larger amounts of water and can increase the humidity by an overly large amount.
9
Research area 4 - The Vivarium.
There are various forms of vivarium, including:
Aquarium - simulating a water habitat; for instance a river, lake or sea; but only the submerged area of these natural
habitats. Plants in the water will use some nitrogen present within the system, and will provide areas for organisms
to hide and forage.
Insectariums - containing insects.
Formicaries - with species of ants.
Paludarium - simulating a rain forest or swamp environment. It also can be seen as an aquarium interconnected
with a terrarium, having both the underwater area as well as the shore.
Riparian - a Paludarium with circulating current through different-levelled pools
Terrarium - simulating a dry habitat, for instance desert or savannah. A terrarium can also be formed to create a
temperate woodland habitat, and even a jungle like habitat. This can be created with pebbles, leaf litter, and soil. By
misting the terrarium, a natural water cycle occurs within the environment by condensation forming on the lid
causing precipitation. Plants suitable for this type of terrarium environment include moss and tree seedlings. Many
kinds of plants are suitable for these habitats, including bromeliads, African Violets and Crassulaceae. Animals
commonly held for observation include reptiles, amphibians, insects, spiders, scorpions, and small birds.
Size and materials
Vivarium with epoxy-coated plywood walls It is usually made of a clear container (often plastic or glass).
Unless it is an aquarium, it doesn't need to withstand the pressure of water, so it can also be made out of
wood or metal, with at least one transparent side. The new fashion in vivariums are those constructed from
epoxy-coated plywood and fitted with sliding glass doors. Coating the inside of a plywood vivarium helps to
retain the natural effect of the environment. Epoxy-coated plywood vivariums retain heat better than glass
or plastic enclosures and are able to withstand high degrees of humidity. They may be cubical, spherical,
rectangular, or other shapes. The choice of materials depends on the desired size and weight of the entire
ensemble, resistance to high humidity, the cost and the desired quality.
The ground surface must be calculated to be enough for the species living inside, at their adult size. The
height can also be important for the larger plants, climbing plants, or for tree climbing animal species.
The width must be big enough to create the sensation of depth, both for the pleasure of the spectator and
the good of the species inside.
Most used substrates are : common soil, small pebbles, sand, peat, chips of various trees, wood mulch,
vegetable fibres (of coconut for example), or a combination of them. The choice of the substrate depends
on the needs of the plants (type of ground), or of the animals (need to dig galleries for example), moisture
(resistance to mould, conservation of water), the risks involved (e.g. the risk of absorption by an animal)
and aesthetic aspects. Sterile vivariums sometimes used to ensure high levels of hygiene (especially
during quarantine periods), generally have very straightforward, easily removable substrates such as paper tissue, wood chips and even newspaper.
Research area 5 - Animal Requirements.
Reptile Heating:
Reptile heating is an extremely important factor in the success of keeping a pet reptile. It can be one of the main reasons to ensure the reptile has a long and healthy life, however
there are many factors involved in the process of heating a reptiles housing. So I will have to take each of them into account before attempting to make a product.
The Reason For Heating:
Due to the fact that the majority of reptiles come from warm climates it is necessary for a reptile keeper to replicate their natural living environment within the housing created for
them. The reason for keeping a high temperature in a reptile’s vivarium is because reptiles are ectothermic (cold blooded) creatures that cannot regulate their own body
temperature meaning that they use the environment they are in to heat their body. Not only does a warm temperature keep the reptiles warm it also aids the digestion process,
therefore it is imperative that a reptiles vivarium is heated correctly. This means that the system must work the majority of the time and if it breaks, it should possess a backup
system that not only attempts to keep the vivarium in check but alerts the pet owner to the problem so the reptile is exposed to non-ideal conditions as little as possible.
Temperature Gradient:
A reptiles cage should have a temperature gradient within its housing that allows for a warm and a cool area, this is to allow the reptile hosed within the tank to move to a
temperature where they feel comfortable. The benefits of this mean that reptiles can move to the hot area of the tank after a meal so the heat can help them
digest their food quicker. An average reptile temperature within a housing should be no cooler than 20°C and no warmer than 32°C to ensure a good
temperature variation within the tank. This
could be created by using a heating system on the floor of the vivarium to crate a vertical temperature gradient.
Hotspot:
A hotspot is an area within a reptiles housing that has a higher temperature than the rest of the reptiles tank, this helps to provide a temperature gradient as stated above. This
means I will have to centre the majority of my heating system into one area.
Humidity:
Different reptiles require different humidities due to changes in their habitat for example the majority of snakes live in dry areas and so require a low humidity, however a poison
dart tree frog lives in rainforest and as such requires a high humidity. This is due to the fact that reptiles/amphibians are specifically adapted to their respected habitats.
Components.
Despite their scales reptiles are still vulnerable to injury, this means the my device will have to be as safe and/or enclosed as is possible. Below I have listed a few
safety hazards my product will face along with possible solutions:
•Sharp objects in the vivarium – conceal all sharp objects within the casing and round off all edges of the casing.
•Exposed wires/visible wires – make sure all wires are connected up safely and ensure no loose wires are disconnected, if they are they must be covered up to
conceal the wire itself. Also any visible wires within the vivarium must be fixed in place due to excessive movement might cause a reptile such as a snake to attack
the wire thus endangering it further.
•Exposed heating/cooling surfaces – these can be particularly dangerous, an exposed heating surface could cause contact burns on the reptile itself, whilst if a
reptile is caught on a cooling surface it could freeze to death before the pet owner noticed.
•Holes – my product might require hole being made in the walls of a vivarium, however if these holes are too big and/or weaken a wall surface this could give the
reptile a way out of the vivarium into the colder air outside, or even into more danger caused by the outside world.
•Moving objects – if an object is in motion and is visible to a reptile, such as a snake, it will cause the reptile to strike the object assuming it to be food and/or a
threat. This could cause not only faulty components but also damage to the reptile if It is caught within the moving objects.
Light:
Some reptiles prefer a certain level of U.V. lighting in their vivarium, this can be accomplished by the addition of a U.V. lamp, these are pretty low costs and highly cost effective, however these are unnecessary and could cause problems
with the heat gradient of the vivarium itself, thus I have decided to not include the U.V. lighting within my circuit.
10
11
Research area 6 – extra research - fixing.
Knock Down Joints.
PLASTIC CORNER BLOCK (FIXIT
BLOCKS):
The corner block is pressed against
the two pieces of material (normally
wood based). Screws are used to fix
the block into position. This type of
joint is used to fit modern cabinets
such as those found in a kitchen. It is
a relatively strong joint although it
has the advantage that it can be
dismantled using a screwdriver.
NATURAL WOOD FITTING (SQUARE
SECTION BATTEN):
A piece of material such as pine can
be drilled and screws can be passed
through these holes. This gives a
cheap and effective knock-down
joint. The screws are normally
countersunk into the knock-down
fitting.
TWO BLOCK FITTING (LOK-JOINTS): These are made from
plastic. A bolt passes through the first fitting into the thread
of the second. As the bolt is tightened it draws the two fittings
together. The pins help keep the fitting straight. This gives a
very strong joint and it can be dismantled using a screwdriver.
RIGID JOINT: These are normally
moulded in plastic which makes
them strong. Screws pass through
the four holes which hold the sides
at each corner firmly together.
Adhesives.
Adhesive or glue is a compound in a liquid or semi-liquid
state that adheres or bonds items together. Adhesives may
come from either natural or synthetic sources. Some
modern adhesives are extremely strong, and are becoming
increasingly important in modern construction and industry.
The types of materials that can be bonded using adhesives
are virtually limitless, but they are especially useful for
bonding thin materials. Adhesives usually require a
controlled temperature to cure or set. They can be
electrically and thermally conductive or insulative.
Pressure sensitive adhesives (PSA) form a bond by the application of light pressure to marry the
adhesive with the adherent. They are designed with a balance between flow and resistance to
flow. The bond forms because the adhesive is soft enough to flow (i.e. "wet") the adherent. The
bond has strength because the adhesive is hard enough to resist flow when stress is applied to
the bond. Once the adhesive and the adherent are in close proximity, molecular interactions, such
as Van der Waals forces, become involved in the bond, contributing significantly to its ultimate
strength.
PSAs are designed for either permanent or removable applications. Examples of permanent
applications include safety labels for power equipment, foil tape for HVAC duct work, automotive
interior trim assembly, and sound/vibration damping films. Some high performance permanent
PSAs exhibit high adhesion values and can support kilograms of weight per square centimetre of
contact area, even at elevated temperature. Permanent PSAs may be initially removable (for
example to recover mislabelled goods) and build adhesion to a permanent bond after several
hours or days.
Removable adhesives are designed to form a temporary bond, and ideally can be removed after
months or years without leaving residue on the adherent. Removable adhesives are used in
applications such as surface protection films, masking tapes, bookmark and note papers, price
marking labels, promotional graphics materials, and for skin contact (wound care dressings, EKG
electrodes, athletic tape, analgesic and transdermal drug patches, etc.). Some removable
adhesives are designed to repeatedly stick and unstick. They have low adhesion and generally
can not support much weight.
Pressure sensitive adhesives are manufactured with either a liquid carrier or in 100% solid form.
Articles are made from liquid PSAs by coating the adhesive and drying off the solvent or water
carrier. They may be further heated to initiate a cross-linking reaction and increase molecular
weight. 100% solid PSAs may be low viscosity polymers that are coated and then reacted with
radiation to increase molecular weight and form the adhesive; or they may be high viscosity
materials that are heated to reduce viscosity enough to allow coating, and then cooled to their
final form. Mayor raw material for PSA´s are acrylate based polymers.
Plastic wrap displays temporary adhesive properties as well.
Research area 6 – extra research – Components.
I have researched the different components I may require, they're prices, availabilities and tolerances. This will give me a general overview of what components would be best suited to my product.
Environmental control.
THERMISTORS – these components increase/decrease the resistance upon an increase of the temperature, this is accomplished by the energy of the electrons being increased as the resistive material is heated, this allows them to flow
more freely around the material, thus reducing/increasing the resistive qualities of the material. The resistance increases by a specific constant known as the first-order temperature coefficient of resistance. The equation to work out
resistance from temperature is:
ΔR = kΔT
Where: ΔR = the change in resistance, k = the first order temperature co-efficient of resistance and ΔT = the change in temperature.
If k is the positive coefficient then the resistance will increase as temperature, similarly if k is negative then resistance will decrease as temperature increases. The different coefficients allow us to use thermistor to both increase and
decrease the resistance in a circuit, however each thermistor has its own value of k that cannot be changed. Thermistor tend to be relatively cheap and are easy for me to acquire making the ma suitable device for measuring temperature in
my circuit.
HEATING PADS – in their most basic form these are just strips of high resistance metals, through which a large current is passed, as this current flows through the strips they heat up in accordance to the current, these strips can reach
fairly high temperatures, and can become very dangerous very quickly if not properly covered up. The heat produced is calculated using the following equation:
where Q is the heat generated by a constant current I flowing through a conductor of electrical resistance R, for a time t. this shows that the temperature is equivalent to the current squared, multiplied by the resistance of the material and
then this is then multiplied by the time the current is applied for. Using this formula we can calculate the maximum temperature we want the strips to reach, to ensure that the vivarium doesn’t overheat, nor will the strips burn through their
protective coating, endangering the reptile. Despite the extreme safety precautions these heating pads are reasonably priced and easy to access, or even manufacture by hand.
MAINS CONNECTION – this would allow me to connect a mains powered component into my circuit this would allow for a higher voltage supply.
Processing.
PROGRAMMABLE INTERFACE CONTROLLERS (PICS) – these are programmable chips that will hold a set amount of data within them, this data will tell them how to operate when certain scenarios occur (example: temperature dropping
below preferred value) these components use a software on the computer known as livewire. Using these allow for complicated systems to be made with relative ease, whilst also lowering the amount of components and hence the price
and reliability.
TRANSISTORS - these amplify the current allowing for a low amp output from a set component (e.g. a PIC) can operate a high ampage component such as a motor. These also allow things to be activated and de-activated.
Inputs.
VARIABLE RESISTOR – a resistor that allows the user to change its resistance, this will allow for an alteration in the set value that will decide the temperature limits if used in a potential divider . These are cheap and extremely easy to
acquire, and thus are of great use in any circuit, however a rotating panel on my product might be altered by the reptile if it is housed internally, this could cause large implications.
PUSH TO MAKES (PTM) – these are simple push to use switches, they make a connection when pressed and break it when released, they are useful for singular inputs or even multiple inputs with limited effects, they are of great use in a
code or a number pad.
12
13
Specifications.
What?
Why?
Evidence.
Must accurately measure and control temperature.
To ensure a safe temperature for the reptile to live in.
Page 10: paragraphs 1-4.
Must control the humidity within the vivarium.
To ensure a maximum comfort for the reptile, the reptile
should, ideally, have the same humidity within the vivarium
as is in its natural habitat.
Page 5: questionnaire results.
Page 10 paragraph 5
Must strongly attach to the vivarium, whilst still being
removable.
To ensure that the system can stay in the vivarium without
risk of potential harm to a reptile by collapse.
General Knowledge.
Must have no sharp edges.
Sharp edges could easily cut the soft underbelly of a reptile.
Page 10: components paragraph.
Must leave no wires bare or easy to bite through.
A bare wire and/or an easy to bite wire could cause the
potential hazard of electrocution occurring to the reptile.
Page 10: components paragraph.
Must have no exposed heating or cooling components.
Can cause the potential for the reptile to freeze/overheat if
it gets caught on the component.
Page 10: components paragraph.
Any holes made in the vivarium must not be too large.
Larger holes might let smaller reptiles escape the vivarium
risking it damage from the outside world.
Page 10: components paragraph.
There must be no moving objects within the vivarium.
Moving objects will not only cause a risk to the snake by
potential collision but also, a predatory reptile such as a
snake, might mistake the object as a threat and/or food and
will, as such, attempt to bite the object, either endangering
the animal or causing damage to the system.
Page 10: components paragraph.
Must be able to alter the temperature and humidity limits.
Different reptiles will have different requirements of heat
and humidity.
Page 10: paragraphs 1-5.
Must be easy to use.
People might not be able to use the system if it is too
complicated of use.
General Knowledge
Must have an alerting system if anything fails.
So consumers will know when something requires a
replacement and/or repairs.
General Knowledge
Must have a backup system if anything fails.
To ensure the reptile is not harmed whilst the system is
down.
General Knowledge
Must be able to be converted from bespoke into batch or
mass production.
To allow for adequate marketing.
General Knowledge
Introduction To Ideas.
Ideas.
The next stage of progress is the designing of the ideas, these ideas will consist of in depth explanations of how the circuit works, the advantages that idea has above the others, or any disadvantages it may have, these will also allow me to
decide which ideas are more suitable for my design. I have decided that instead of approaching each idea as a whole design idea I will explain each sub-system in detail and then choose not only the most efficient subsystems to make the
final, whole, idea but also the subsystems that are the most compatible with each other. There are numerous different sub-sections that need to be addressed, but I will address them in groups which are:
• Temperature sensing and processing.
• Temperature modification.
• Humidity sensing and processing.
• Humidity modification.
• User interfacing.
• Casing of the design.
• Attachment of the case into a vivarium.
• Power supplies.
These subsystems are shown in this diagram, with all the basic idea titles that I will be including. in my ideas section.
14
Ideas, subsection 1 – Power.
1. Temporary battery power, through a voltage regulator to produce a 5V DC supply.
A normal pp3 battery produces a 9V DC supply without the
capability of high current. By running this through a voltage
regulator I can produce the steady 5V DC supply that is
required to run my PIC, this will however decrease the current
available from the battery. while they supply a decent voltage
at low amps batteries have a short shelf life, even if
rechargeable, this means that the user will have to pay to
keep the product running when the battery runs out.
Batteries however can be integrated into the case (as long
as they can be easily removed by a user) allowing the product
to become fully portable, most batteries take up very little space, the pp3 battery is approximately
48 mm × 25 mm × 15 mm so if integrated into a case there would be little if any need to increase the
size of the case. by working out the ampere hours of the circuit you can calculate how long the battery
will last for. because the battery only has a set voltage and current it is practically useless as a supply to
any heavy duty items such as heathers or motors, however it is a highly adequate supply for processing
signals as this is very low duty and thus will not wear out the battery too quickly.
2. Mains 240V AC supply.
Every house in the UK is connected to a mains supply and so it
is a readily available supply of energy. the mains supply can
supply massive amounts of current to a circuit making it the
perfect supply to use on heaters, motors and other heavy duty
components that require rather large amounts of power.
However in order to be used for lower duty components it would
require passing through a transformer to lower the voltage
(see section on transformers.) A high voltage and current make
this idea extremely flexible, however it involves a high level of
danger to myself.
3. Solar.
This would only be useable as a backup supply of power or as
a charger for the main source (if it’s a rechargeable battery)
solar would be of use in my project as the majority of
vivarium use a lamp to provide a light source for the reptile
to provide a sense of night and day, so while the lamp is on
using solar panels on the upper face of the casing would
re-use a miniscule amount of the light energy provided by the
lamp as electrical energy for my system making it more
energy efficient.
4. Permanent battery power, through a voltage regulator to produce a 5V DC supply.
This design is almost identical to the temporary battery,
however the user would not be able to remove the battery
from the casing without totally dismantling the case, this
prevents the removing of the battery by children, or by
animals, but causes the issue of not being able to remove
an empty battery. Due to the lack of ability to remove the
battery this system would require a rechargeable battery,
this idea would also provide a professional look to the
product. This power supply is often used in mp3 players
and ipods.
5. Dynamo.
A dynamo is basically a motor in reverse, it converts
rotary mechanical energy into electric energy using a
magnet and a coil of wire. This supply could only be
viably used in conjunction with a fan for the cooling
system as it could be attached to one end of the fan
causing a feed back of a small amount of energy from
the motor being used to rotate the fan. This, like the
solar panels, could not viably be used as a full power
source, however it would be able to charge a battery
or could be used as an emergency backup generator.
6. Transformers.
Not a power supply in themselves but they can be used to
step-up, or step-down the voltage and current of other supplies
(such as the 240V mains supply to generate a 12V supply).
these are of great use when running two circuits that both
require different power supplies (such as a 12V circuit activating
a 240V circuit via a relay.) However transformers require a supply
of AC as the electromagnetic effect cannot be established with
a DC supply, similarly they also can only emit AC, however this
can be altered into a DC supply by using a bridge rectifier diode
setup.
15
Ideas, subsection 2 – Temperature measurement and processing.
1. Thermistor with operation amplifiers and potential dividers. This circuit consists of two potential
dividers, one using a variable resistor to allow a limit to be set (PD 2) and the other using a thermistor to
measure the temperature in the vivarium (PD1), these potential dividers are then compared by two
operation Amplifiers (OP-AMPS). Depending on whether the temperature is high enough to allow a
voltage from PD1 that is larger than the one produced in PD2, through to the OP-AMP then the cooling
system will switch on, while at the same time the heating system will be switched off. However when the
temperature is too low, the voltage from PD2 is greater than that from PD1 and so the cooler is turned
off and the heater is turned on. This occurs due to the set up of the two OP-AMPS, the first is set up so
it will supply a positive voltage if PD1 is greater than PD2 but a negative if it is smaller, the second
OP-AMP however is connected in the opposite way, so when PD 1 is of a higher value than PD2 it
supplies a negative voltage, but supplies a positive voltage if PD 1 is lower. When a positive voltage is
released from the first OP-AMP into transistor 1 (T1), the transistor
allows current to flow from its collector to its emitter activating
D
the relay for the cooling system (RLY1). Whereas if a positive
R
R
voltage is released from the second OP-AMP then it activates
R
D
TR
T2 allowing current to flow through activating RLY2 for the
OPAMP
heating system. This circuit will measure the temperature by
R
R
altering the first resistor value in PD1, thus altering the voltage
OPsignal (Vs). This Vs is then compared against the Vs from
R
AMP
another potential divider set at a constant value, until changed
TR
by user input. When temperature is higher the resistance of
the thermistor decreases, thus increasing the V s for that
potential divider. This circuit will allow for an accurate
measurement and processing of temperature value, comparing
it against a set limit and activating the heater/cooler
respectively, while also preventing both the heater and the cooler being active at the same time. The
main problems with this circuit are that is has no settable timer to receive values from the PDs so every
flux in the temperature is measured, so a small change in temperature, that might not need noticing can
cause the heater to turn off and the cooler turn on, or visa versa, this circuit will also rely on a split rail
voltage that includes a negative voltage, this can cause issues when manufacturing the circuit board
especially if short circuits occur.
1
1
2
5
2
1
1
4
3
2
6
2
2. Bi-metallic strip breaking a circuit.
This circuit uses a bi-metallic strip to monitor the temperature, because the bottom half of the bi-metallic
strip (in this case copper or Cu) has a higher expansion rate than the upper half (in this case iron or Fe),
the Cu expands at a faster rate than the Fe as the temperature increases, however they are bonded
together and fixed into a solid support at one end, thus the Cu expands and bends the bi-metallic strip
towards the Fe, using this I can place a push to brake (PTB) in the path of the bending strip, thus
setting a temperature limit. While the PTB is not pressed by the bi-metallic strip, current passes to the
base of the resistor activating both it and the relay, while the relay is active the heating system is active
but when the PTB is activated by the bi-metallic strip hitting it, the relay is de-activated and the cooling
system is activated. This system records a wide
range of temperatures, and tiny fluctuations will
not effect the bimetallic strip, so the relay will not
constantly switch on and off, however with the
temperature changes required in the vivarium,
the bi-metallic strip might not be effected due to the
changes being too small, the strip will also require
a time to bend, this could cause complications in the
speed of reactions. The circuit is relatively simple
and easy to manufacture and could be the least
expensive circuit to manufacture, however the
practical offsets made by the bi-metallic strip
greatly outweigh the circuits simplicity and ease of manufacture, and thus it is probably not the best
method for my design.
3. Thermistor with a
Programmable Interface
Controller (PIC).
this Circuit consists of a single
thermistor within a potential
divider that feeds into the analogue
input of the PIC this is then
compared against the voltage of
another potential divider which can
be set to certain values using a
variable resistor. After a set time
the PIC will compare the two
voltages and if the thermistor
provides the higher voltage then
the PIC will only activate relay one,
this in turn will activate the cooling
system, however if the variable
resistor provides the higher voltage
the PIC will only activate relay two
in turn activating the heating
system. attached to seven of
the outputs is a 16pin resistor array set at 220ohms, this resistor array is also connected to seven light emitting
diodes (LED), these seven LEDs provide a user interface display, one LED will be used as a power light
showing that the system is active the other six are temperature representative, if the air is too cold, only the first
two will light, if it is within the boundaries of limitation that have been set then the second pair will light, so four
LEDs are lit and finally if the temperature is too hot, all LEDs will be lit, these six LEDs will be colour coded, two
green to show cold, two orange to show acceptable and two red to show too hot.
4. Thermocouple with two Operational Amplifiers used
as comparators.
Thermocouples (TC1) induce a current dependant on the
temperature this voltage is then compared against the voltage
from the first potential divider (PD1) in OP-AMP1 if the
voltage induced is larger than that from the first potential
divider then OP-AMP1 produces a positive voltage, this voltage
will activate TR1 which allows current to flow through TR1 this
activates the first relay (RLY1) which controls the cooling
system, however if the voltage induced from TC1 is smaller
than that of PD1, OP-AMP1 will supply a negative voltage to
TR1, this will however not activate it, so RLY1 will not be
activated and the cooling system remains switched off.
the voltage induced from TC1 is also compared against
the second potential divider (PD2) by OP-AMP2 however
if the voltage induced from TC1 is larger than that from PD2 then OP-AMP2 supplies a negative voltage to TR2
so both TR2 and RLY2 remain inactive and thus the heating system remains inactive, however if the voltage
induced from TC1 is lower than that of PD2, OP-AMP2 will produce a positive current to TR2 allowing current to
pass through, activating RLY2 and in turn activating the heating system. Because TC1 produces a voltage
dependant upon the temperature it is a consistent monitoring of the temperature, however the voltage increase
from the small temperature increases in my design could be difficult to limit, due to limitations upon the resistors
in the potential dividers.
16
Ideas, subsection 2 – Temperature measurement and processing continued
Ideas, subsection 3 – user interfaces
Ideas, subsection 4 – temperature control.
5. Thermistor through a potential divider into a PIC controlled by a rotary switch into 5 inputs.
A change in temperature is recorded by the
thermistor within the potential divider, this
then produces a signal which is recorded
by the PIC. Depending on which input is
activated by the rotary switch, the signal from
the potential divider is compared against a
set value range specific to which of the digital
inputs on the PIC is activated. this allows for
a multitude of set ranges for the temperature
within the vivarium with relatively easy use.
However this will use every input into the PIC
with the only exception of one analogue input
this will thus prevent any extra inputs if
necessary.
1. Two seven-segment LED displays
displaying the temperature at a specific
point of time.
Using further research into the temperature
ranges and their specific values from the
potential divider with the thermistor in (this
is going to be necessary in the project with
or without this interface) I can program the PIC
to generate a number of pulses depending on
value (approximately equal to the temperature)
so this value can then be counted by two
4018’s providing the 7-segment LEDs with
current to the correct pins in order to display
the approximate temperature value, another
output from the PIC would reset the 7-segments
this operation would occur every time the PIC
Checked the temperature.
2. Six Led’s providing a coloured scheme display to show
relative temperature to set values.
When the temperature is monitored by the PIC depending on
which operation the PIC must perform it will send two signals
to two specific LEDs through the resistor array the LEDs will
be coloured in a specific order (see figure right) this shows
whether the temperature is cold (G), just right (A) or too warm
(R). this will allow the user to note as to whether
the system is faulty, or if it is safe for use at that
specific moment (when first set up). This interface
would best be used in conjunction with idea no. 5
of the systems for monitoring of temperature as the
use of macros would enable easy use of set
programs and the idea in speculation is very easily
adapted to using macros. This interface is relatively
easy to manufacture and for use by the user.
1. Underground heating.
Using a system in which the heating is on the bottom
floor of the vivarium (either built into the base, or kept
under the woodchips) allows for the heat to travel
through the vivarium by convection, this will induce a
temperature gradient throughout the vivarium with
higher temperatures at the bottom and lower
temperatures along the roof, however it will take time
for heating effects to take place and at lower
temperatures the heating effect may not reach the top parts of the vivarium at all. This system is also
inefficient due to the heat wastage in the convection, however it is easy to construct and relatively
inexpensive.
2. Cooling by increased ventilation.
Increasing the ventilation of the vivarium would rapidly cause a decrease in temperature (down to that
of the rooms ambient temperature) this would be useful
as long as the ventilation holes were either covered by
the product OR covered by a fine mesh small enough so
while air can still traverse through, neither the reptile nor
its respective food can escape. By using a metal panel
(as shown) we can monitor the amount of ventilation
And thus maintain the amount of relatively cool air
Being let into the vivarium. An increase of cool air
entering the vivarium would cause a decrease in the
time taken for the temperature within the vivarium to fall
whereas less air would cause the temperature to fall less
rapidly. A rotary fan may also be used.
3. Fish tank heaters.
By conducting research about existing products, I found
that fish tank heaters are an efficient method of increasing
temperature within an isolated environment. Connecting the
heater to a supply that can automatically alternate between
on and off would be simple enough if used with a relay but
could be very complicated if done in other ways due to the
requirement of a power supply consisting of 240V A.C.
Using a fish tank heater outside of water however will
cause the casing to crack and break, preventing the heater itself from functioning and
could cause large issues to the reptiles safety due to broken glass and potentially hot
surfaces. However if the heater is encased in liquid (for example water (H 2O)) which is contained by a
glass or polymeric case the heater will not break and the liquid will allow for the heat to travel by
convection through the casing into the vivarium heating the entire isolated environment.
4. The conduction of heat using water.
Because water is a good conductor of heat it can be
used to convey the heat produced around the entirety
of the vivarium equally. The heat could be produced
using one of the above methods, this system however
will require the construction of an entire vivarium and
will provide no temperature gradient.
5. Heating effect by power wastage.
When current is passed through a circuit with
resistance, some power is lost from the circuit as heat,
while this is a problem in most circuits it may have a
use in mine. If I can contain the metal (preferably
copper) strips in a conducting material, so the heat can
escape but the reptile wont run the risk of burning itself on the strips themselves. There is an equation
to calculate the power lost as heat in a circuit in Watts, this equation is shown below, and is also
converted to include the resistivity of copper strips;
Pw = I2R
Pw = I2ρSal
Pw = I2ρV
Where Pw is the power in Watts, R is the resistance of the circuit, I is the current of the circuit, ρ is the
resistivity of copper, Sa is the surface area of the copper strip, l is the length of the copper strip and V is
the volume of the copper strip. This equation allows me to alter the heat output of the circuit, while it
would be difficult and expensive to alter the volume of copper in the equation I can easily alter the
current and/or voltage of the circuit to increase/decrease the heating output.
17
Ideas, Development of idea - Circuitry.
Thermistor through a potential divider into a PIC controlled by a rotary switch into 5 inputs.
A change in temperature is recorded by the
thermistor within the potential divider, this
then produces a signal which is recorded
by the PIC. Depending on which input is
activated by the rotary switch, the signal from
the potential divider is compared against a
set value range specific to which of the digital
inputs on the PIC is activated. this allows for
a multitude of set ranges for the temperature
within the vivarium with relatively easy use.
However this will use every input into the PIC
with the only exception of one analogue input
this will thus prevent any extra inputs if
necessary.
Reasons:
For Allows for preset “allowable” temperature ranges to give reptile a variety of temperatures to
allocate its preferences.
Enables security of temperature range, as the rotary switch is less likely to be accidentally
turned than a variable resistor.
Very specific design allows for concentration to be allocated on its main functioning.
Not overly complicated circuit.
Against Design is very specific limiting the amount of variations available to make product more
diverse.
Very few spare inputs stop use of extra controls
Quite sizeable circuit board would be required.
Heating effect by power wastage.
When current is passed through a circuit with
resistance, some power is lost from the circuit as heat,
while this is a problem in most circuits it may have a
use in mine. If I can contain the metal (preferably
copper) strips in a conducting material, so the heat can
escape but the reptile wont run the risk of burning itself on the strips themselves. There is an equation
to calculate the power lost as heat in a circuit in Watts, this equation is shown below, and is also
converted to include the resistivity of copper strips;
Pw = I2R
Pw = I2ρSal
Pw = I2ρV
Where Pw is the power in Watts, R is the resistance of the circuit, I is the current of the circuit, ρ is the
resistivity of copper, Sa is the surface area of the copper strip, l is the length of the copper strip and V is
the volume of the copper strip. This equation allows me to alter the heat output of the circuit, while it
would be difficult and expensive to alter the volume of copper in the equation I can easily alter the
current and/or voltage of the circuit to increase/decrease the heating output.
Reasons:
For Is capable of giving large amounts of heat out.
Not overly expensive, especially if made by hand.
Quick response to alteration of the circuit.
Allows for a varied heating effect.
A prebuilt “heat mat” can be used.
Against High energy running costs.
“Heat mats” can be expensive.
Requires 240V AC supply. (mains.)
My cause damage if metal is not insulated properly.
Six Led’s providing a coloured scheme display to show
relative temperature to set values.
When the temperature is monitored by the PIC depending on
which operation the PIC must perform it will send two signals
to two specific LEDs through the resistor array the LEDs will
be coloured in a specific order (see figure right) this shows
whether the temperature is cold (G), just right (A) or too warm
(R). this will allow the user to note as to whether
the system is faulty, or if it is safe for use at that
specific moment (when first set up). This interface
would best be used in conjunction with idea no. 5
of the systems for monitoring of temperature as the
use of macros would enable easy use of set
programs and the idea in speculation is very easily
adapted to using macros. This interface is relatively
easy to manufacture and for use by the user.
Reasons:
For Allows display of relative temperature, thus suiting the temperature recording system as it
can show if, for the selected input, whether the temperature is too low, high or just right.
Easy to integrate into a circuit.
Cheap cost due to low price of LEDs
Simple design makes it easy for consumer use.
No further research is required in order to use this option.
Against simple design might make design seem less professional.
May cause problems if the temp range is set wrong as no indication of true temperature.
Will not satisfy and user curiosity of the temperature.
18
Ideas, Development of idea.
Temporary battery power, through a voltage regulator to produce a 5V DC supply.
A normal pp3 battery produces a 9V DC supply without the
capability of high current. By running this through a voltage
regulator I can produce the steady 5V DC supply that is
required to run my PIC, this will however decrease the current
available from the battery. while they supply a decent voltage
at low amps batteries have a short shelf life, even if
rechargeable, this means that the user will have to pay to
keep the product running when the battery runs out.
Batteries however can be integrated into the case (as long
as they can be easily removed by a user) allowing the product
to become fully portable, most batteries take up very little space, the pp3 battery is approximately
48 mm × 25 mm × 15 mm so if integrated into a case there would be little if any need to increase the
size of the case. by working out the ampere hours of the circuit you can calculate how long the battery
will last for. because the battery only has a set voltage and current it is practically useless as a supply to
any heavy duty items such as heathers or motors, however it is a highly adequate supply for processing
signals as this is very low duty and thus will not wear out the battery too quickly.
Mains 240V AC supply.
Every house in the UK is connected to a mains supply and so it
is a readily available supply of energy. the mains supply can
supply massive amounts of current to a circuit making it the
perfect supply to use on heaters, motors and other heavy duty
components that require rather large amounts of power.
However in order to be used for lower duty components it would
require passing through a transformer to lower the voltage
(see section on transformers.) A high voltage and current make
this idea extremely flexible, however it involves a high level of
danger to myself.
I have decided to use the two power inputs as my circuit requires two separate voltages the mains
supply can provide enough voltage and current to run the heater whilst the batteries can provide the low
voltage – low current requirements of the PIC.
My circuit could not include humidity control as this was unfeasible within the time constraints and with
schools supplies.
19
Ideas, Development of design – PCB programming design.
20
21
PCB Development.
The first section of my development is to design and develop a printed
VR1
circuit board (PCB). This is the base for my entire
circuit to be on and will give an impression as to the
C1
size of my overall product. To design the PCB I used a
R1
C2
piece of software on the computer called “PCBwiz.” As
with any circuit I began by creating a power source (fig1)
(this can be moved at later times to shrink the PCB
T1
if necessary). Due to the fact I am using a 9V battery
fig1
to supply my PIC processing unit (which requires a steady 5V supply) I
will have to include a voltage regulator within my power source which
will lower the supply to a steady 5V. to connect the battery into the
circuit I am using a terminal block (T1) mounted on the PCB in which I
will connect a “battery snap” to provide power to the circuit. The
positive volts from the battery will be fed through a diode (D1) into the
voltage regulator (VR1). In order for the voltage regulator to function it
requires two 10µF capacitors (C1 and C2) connecting both of its outer
pins to 0V (on my circuit board this is direct to the 0V side of my
batteries terminal block, however this can be done at any point on the
0V rail). After I had designed my power source I decided my next step
would be to connect my PIC to the power
R1
DIL2
C3
and to the LED display (fig2). For my LEDs
I am using 7 terminal blocks (T2-8) conne- T9
fig2
cted to the PIC through 14 pins of a 220Ω
T2
resistor array, the 0V legs of the LED
DIL2
terminal blocks are connected together and T3
then to the 0V supply from the battery to
T7
T4
save space on the PCB, the outputs for the
T6
T5
7 LEDs are outputs 0-6, or pins 6-12. Pin 5
T5
of the PIC is connected directly to 0V while
pin 14 is connected directly to +V and then to 0V by a 10µF ceramic
capacitor (C2). Finally pin 4 on the PIC (reset) is connected to +V
through a 10kΩ resistor (R1) and then to 0V through a Push To Make
switch (PTM) that is connected by a ninth terminal block (T 9). After
T11
this had been completed, the next step was to
R3
T12
T10
connect my PIC to the rotary switch to determine
R7
the limits of the analogue signal produced by the
R6
R5
temperature and to the potential divider providing
R4
R8 the analogue signal for processing
R5
(fig3). the rotary
switch is connected by using three terminal block
R1
C3
(T10-12) in a ┴ shaped pattern, the topmost
T9
fig3
connection will be the common connection while
the other 5 connections will be normal poles of the switch. each
connection of the switch is connected to 0V through a 10kΩ resistor
(R2-6) and directly to the input pins of the PIC (pins1-3 + 15-16 or digital
inputs0-4). The potential divider is connected to pin 17 (analogue input0)
of the PIC, with the negative coefficient thermistor, connected using a
terminal block (T13) connected to +V and the 10kΩ resistor (R7)
connected to the bottoms of two other 10kΩ resistors (from the rotary
switch) then to 0V through a 0Ω resistor (R8).
D2
No
My next, and final, step is to add the relay switch (RLY1) to the PIC
+V
and the power supply. On the relay there are 5 pins normally open
(No), normally closed (Nc), common (Co) and the two power pins
Co
(+V and 0V). Pin +V is connected to the +V supply and has a diode
T14
Nc
(D2)(polarised against the +V supply) to prevent the relay from
0V
blowing, the 0V pin is connected to the collector of a high gain transistor (TR1). The base pin of the transistor is connected to pin 13
R8
(output7) of the PIC through a 1KΩ resistor (R9) which acts to protect
C3
the transistor, the emitter pin of the transistor is connected directly to
R9
0V. For the switching pins of the relay I have connected pin Co to a
leg of a terminal block (T14), pin No to the other leg of the same
TR1
terminal block and finally pin Nc is connected directly to 0V. This
layout causes the heater attached to the terminal block to receive voltage from its supply when the relay is activated,
however when the relay is closed, nothing will occur as there is no connection between the two pins of the terminal
block. I am now left with a complete circuit on the PCB, however with too many white
gaps a lot of copper would be wasted, so my next job is to “block in” the circuit to
save on the cost of copper. while blocking my circuit I noticed a gap between my
thermistor’s terminal block and the positive volt rail, this would cause a major
problem in my circuit, however it is easily fixed during designing, to fix this problem I
simply blocked over the gap making the connection in that way. in addition to
blocking I also placed my initials onto the circuit for identification reasons. I am now
left with a complete circuit board PCB wasting as little copper as is possible given the
size of my circuit.(fig6)
Now that I have completed my PCB I am finished designing and can move on to development and
manufacturing.
22
Manufacture plan.
Tasks.
Time required for task.
Materials and processes.
Health and safety.
Quality control.
Final checks of the PCB design on a
computer prior to printing design onto
an acetate sheet.
Computer
PCB software.
N/A
Receive supervisors appreciation of the
PCB design.
Printout PCB design onto acetate
sheet.
Computer
PCB software
Acetate sheet
Printer and ink
Low amounts if any.
Check the quality of the printout is
acceptable, with no smudges or
unwanted gaps.
Develop PCB within UV box.
UV box
Cut to size photo etch board
Acetate.
UV light so minimise exposure, and
240V equipment.
Develop for the appropriate time. (ask
supervisor if unsure)
Etch PCB in chemical bath.
Chemical bath
Developing solution
Developed PCB
Corrosive acid is being used so
protective guards must be used.
Use of the correct concentration of acid
and etch for the correct amount of time
(see supervisor for values)
Drilling holes for components.
Pillar drill
PCB
Drill bits
Use a drill guard
Wear safety goggles
Tie hair back with bobble
Ensure to take time while drilling to
increase accuracy of drilling, ensure
use of correct size drill bit and check
drill holes after.
Clean with steel wool.
Steel wool
PCB
Wear goggles at all times.
N/A
Solder in components.
Components
PCB
Soldering equipment
Flux
Wear goggles at all times.
Be careful to avoid touching iron.
Always replace iron in holder.
Use flux to assist soldering.
Use correct solder amount
Try not to burn components.
Solder and attach flying leads
Components
Multi-core wire
Soldering equipment
Screwdriver
PCB
Use “helping hands”
Wear goggles at all times
Avoid touching iron
Always return iron to holder
Use shrink-wrap tubing to insulate.
Programme PIC
PIC programming software
PIC programmer
PIC
N/A
N/A
Snagging.
Multimeter.
Signal probe
Repair equipment.
Battery.
N/A
This is all Quality control.
Product Development.
•Firstly I needed to check my PCB design for any flaws, this is just quality control
of my product, ensuring that it works and functions adequately.
•After this was completed (and double checked by my supervisor) the next step
was to print my design onto a sheet of transparent acetate. This printout would be
the basis of etching my circuit board.
•In order to etch my PCB I had to place the acetate sheet on top of a photo-etch
board, then add both pieces into a UV light box for approximately 2-3 minutes to
develop parts of the board.
•After development in a UV box I placed the photo-etch board in developing
solution to prime the photo-etch board for etching in an acid tank.
•After priming the board I placed the photo-etch board into the acid bath, this would
remove all UV-treated copper from the board. (takes approximately 20mins)
•While the board was etching I connected the loose components (LEDs, battery
snaps and switches) to flying leads.
•I am now left with a completely etched PCB, after washing all acid off the board
the next step is to solder in the components, as in case of mistakes its easier to
start smallest first, the first thing I soldered in was the resistors, directly mounted
onto the PCB board.
•The next components that required soldering were the DIL holders and the
capacitors, no chips are added to the circuit at this point to help avoid any heat
damage.
•After soldering in the DIL holders I inserted my PIC and my resistor array into their
respective holders.
•After I have soldered all my DIL holders and capacitors in the penultimate
components left to solder are the terminal blocks, when soldering these in I noticed
I had left too small a gap for them to fit in, this however was simple to fix my filing
down the wide back of certain ones.
•The final thing to solder to my circuit board is the relay, this is mounted onto my
PCB directly.
•Now I had completed my soldering I attached my flying leads to their respective
terminal blocks and my circuit was complete.
Snagging.
However my circuit had a few flaws in its design, I had placed several tracks too
close to pads and during etching this had left a short circuit, this was easy to fix
however by scoring through the copper using a scribe. I had also soldered in my
transistor the wrong way and the diode above the relay was in back-to-front
causing a short circuit, this meant I had to de-solder and then re-solder both
components, this was highly time consuming.
After fixing these minor issues I had a fully operational circuit board, the
programme used (left) was mildly complex and took a while to configure..
23