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Project Kelvin

DP 263 Product Development Designing Our Futures: Winter warmth Chloe Fong

It started with a clay animation, then the long and winding road of making it work. Feel free to jump about, but reading it chronologically is strongly advised. Some of the work done was a little geeky to put here. So if you are interested in the industrial side of mass production, there’s a book called Supergeek which you would be very interested in.

Kelvin is a personified thermometer that aims to evoke a nurturing response from the user to pay more attention to the status of the plant, and in turn, the ambient indoor temperature. It adds a positive touch to the normally stigmatising health warning by turning the older person into the carer instead of having to be cared for.


Table of Contents

Part One: First Principals


One- Bimetallic Strips Two- Shape Memoty Alloys Back to the Drawing Board Three- Shape Memory Polymers

Part Two: Design Changes


Semiotics Testing New Form Factor Making It Work

Part Three: Third Time Lucky First Concept: Pneumatics Second Concept: Linear Pivot CAM In the Third Dimension Driving the CAM Adapted System Initial CAD A New Problem Limit Switching




Part Four: Looking Good Image Board Material Finish/Tactile Desirability Size of Leaves/Psychosocial Pot Designs Visual Prototypes A Major Problem


Part Five: User Testing The Study Qualitative


Part Six: Final Final This Is Kelvin Further Development References

If you are marking this book, the human factor sections are conviently highlighted in brown above.


Part i: First Principals Making Kelvin work was a little tricky, many ideas and methods where explored to find the perfect way. The first principals relied on material properties of the product itself, without the use of electronics or mechanics. The idea was to minimise the tasks needed for initial set up and upkeep of the product, making it work straight out of the box. The first concept carried on from ideation used bimetallic strips, as that option was not viable, the search went on and came to shape memory alloys and polymers.


One- Bimetallic Strips

Bimetallic strips work by using the difference in linear thermal expansion coefficients between 2 metals, that’s what the physicists call it anyway. In normal terms, that just means the amount a metal expands when heated. By sticking together 2 strips with different expansions, the strip curls because one length is greater than another. The most common materials used for bimetallic strips are copper (Cu) and steel. Cu as a coefficient of 16.6x10-6m/m K, a relative high expansion and Steel (stainless, ferritic) has a coefficient of 9.9x10-6m/m K. (Engineering Toolbox, 2014) To figure out what type and how much of each material is required, we need to look at the movement needed for the two dimensions of the two shapes and their curvatures. The numbers from that was then plugged into the (to me) insanely complicated equation on the next page, and the attempts to get it to work follow.


Basic Thermostatic Bimet 1. General Formulae

A bimetal strip consisting of two components and s the expression 1


6 (α2 – α1) (1 + m)2

– = RT RO 3 (1 + m)2 + (1 + m · n)


m2 + 1 m·n




where RT = Radius at temperature T RO = Radius at temperature TO

s1 m=— s2 where s1 and s2 are thicknesses of the comp E n = —1 where E1 and E2 are moduli of elasticity of E2 α1 and α2 = coefficients of linear thermal expansion

If the thicknesses of the component layers are the sa elasticity are also the same we obtain n = 1. The exp 08



3 (α2 – α1) T – TO

tal Data

subjected to heat alters its curvature according to

T – TO



ponent alloys the component alloys of component alloy I and II respectively.

ame, s1 = s2, we obtain m = 1, and if the moduli of pression [1] can then be simplified to From Kanthall Themostatic Bimetal Handbook , 2008

Curvature of Spirals

Origianl Radius=0.08m 12

Radius at >18C= 0.05m

Using the Copper and Steel as the two materials, the thickness of the material will have to be 9.96m to get the radius change needed. So the plant will have to be quite big and not really feasible. There are ways around this though, if the materials have a larger difference is expansion coefficients, then the movement would be greater. However, after searching and searching and searching, there

are materials that would expand enough, but the material changes state and will not go back to its original shape when cooled. (i.e. foaming certain plastics.) So to sadly conclude, bimetallics strips do not seem like a viable course of action.


Marchon Eyeware, 2012. via

Two- Shape memory Alloys Shape memory alloys (SMAs) are smart materials, and indeed they are smart. The material changes shape with temperature change, a bit like state changes in water. When water is cooled below 0oC, the molecules arrange into a uniform state and the water becomes ice, when heated above 100 water become gas. SMAs have more than the normal 3 states of gas, liquid and solid, in fact, they have 2 solid states: Austenite (at a higher temperature) and Matensite (at a lower temperature), allowing them to switch between the two solid shapes.


When changing between the two states the atomic structure reshuffles, allowing the metal to go from a rigid state (Austenite) to a super elastic state (Matensite), when can be bent to any shape when force is applied.


When heated, the atomic structure is uniform.

+ Cooling = martensite Atomic stucture reshuffles. The Shape memory alloy becomes superelastic.

+ force = deformation SMAs can be deformed easily when cool, and will return to austenite phase when reheated.


Shape memory alloy (nitinol) in action.

Vacuum Arc Remelting. Youtube (2012)

So if the metal changes shape within itself, surely it would be the best option for Kelvin? Well, sadly, no. Unless users would pay a lot of money for it. Currently, Nitinol, the nickel titainium SMA widely used in medical procedures, costs a lot of money to make. The process (Vacuum arc remelting) requires very high heat, argon gas, tons of electricity, specific heat conditions, specific factories, specially trained technicians and, well, you get the drift. 17

back to the drawing board


With Bimetallic strips ruled out, the next concept would make the alert system binary, so the wise opinion of users were consulted.

Q: would you rather the thermometer move gradually with temperature? or a theremometer that will move to tell you if the room is too cold? A: 2 of the 5 users preferred the binary system. 1 would rather it unfurl but would like markings on the plant to tell the temperature and 2 would not mind either way.

The next concepts adopted the binary system. Where the change in shape was no longer gradual, but changes between to distinct forms. The too cold position and the warm enough position.

Three- Shape Memory Polymers Shape memory polymers have not been around for as long as SMAs have been. They are more cost effective as they can be made in a lab and don require the expensive processes. Another good point is they can be programmed to work activate at a range of temperatures as their molecular structure and be easily altered by engineers. When cool, they are in a rigid state, and return to their programmed state when heated.


First things first, SMPs can be “trained� at relatively low temperatures, so a kettle, a fork and some aluminium foil was used to set its memorised shape. The strip of SMP was wrapped around the fork handle, covered in foil, and left in a jug of boiling water for about a minute. The helix shape was held by the foil which became the programmed shape. When the strip had cooled back down, it was flexible enough to roll out straight When heat was added again (using a hair dryer) it coiled back into a helix, the shape it was set to when wrapped around the fork.


SMPs are not only 2.5 times cheaper per kilo compared to SMAs, the also can deform more, and require a lot less stress for deformation; 1-3 MPa instead of 50-200MPa for the alloys. Product of SMPs can also be done in a sub 200C environment as opposed to more than 1000C for SMAs, they also don’t need to be drawn under high pressure to create the original shape. (Liu et al, 2007)

This graph shows the change drop in storage modulus between the two states. The beige bit highlights the transition range of SMPs from rigid to solid. The transition temperature, also known as the glass transition temperature is at the middle of the range.


elastic modulus

Rigid State

Elastic State Transition range

Temperature 24

So it’s cheaper, more customisable, and easier to make. Must be a winner then? Well, that was the initial idea, but after placing an order all the way from America and waiting at the doorstep like an excited puppy, and finally getting to test it, the idea did not seem that viable anymore... There were a few problems with the material. The biggest problem was the material has a one way shape memory, so if the room was warm enough and the plant unfurled, it would not curl back up when the temperature dropped again. So changes were made to try to combat this problem, a hybrid of a bimetallic strip and SMPs concept was hence born. The idea was, instead of using two metals, one of the two strips would be a SMP and another would be a flexible, elastic material, such as silicone rubber. The SMP would be programmed to default at the unfurl position when heated, and the silicone rubber would be moulded at the cold temperature. This meant that when the room was heated over 18C, the SMP would push the flexible silicone to the warm position and when the temperature drops down again the silicone would push the SMP back the cold position. The reason why that didn’t work

either was quite apparent when playing with the little strips of SMP, when heated, the material barely exerts enough force to move back to its programmed position, let alone push the silicone back. Another problem was even if it did exert enough stress to deform the silicone, the SMP would cool and harden, meaning the silicone would need to exert more force to move it back into position. The SMP bimetallic hybrid would only work if the stiffness was reversed between the two states. Another problem of using shape memory materials (both SMPs and SMAs) lies in the rate of temperature change. If you look back at the graph, the actuation temperature for SMPs is actually a range, and there needs to be a large change in temperature for the material to get from the cold position to the warm one. Speaking to a Nitinol (SMA) manufacturer, it was also apparent that the alloys was not a plausible direction to go down.

“…even our low hysteresis nitinol requires a temperature change of 11°C for the shape memory effect to take place.” -Email From Kellogs Research Lab

Bimetalic hybrid theory

Part two: Design Changes And so, yet again, project Kelvin has been sent back to the start. After hitting so many brick walls, it was probably a good idea to go back to the fundamental design of the product, and look at its physical form. A re-design of the form of the product was needed in order to make Kelvin work. An experiment was then drafted up to look at the semiotics of a house plant, ideally the user should be able to tell that Kelvin is a plant, as there is research that shows there is an “…innate emotional affiliation of human beings with other living organisms” (Wilson, 1986) and that having indoor plants can promote

emotional wellbeing (Lohr et al, 1996, Bringslimark et al, 2009.) The idea was to look at what people perceived a potted plant to look like, and if there was any difference between participants in England and participants in Hong Kong. Kelvin should be universally recognised as a plant so language and culture should not become a barrier, as the product could potentially be useful to older people in other countries. (probably not Hong Kong because it’s tropical, but still useful in cross cultural analysis)

The study: 10 Seconds No preparation time Pen and Paper Draw a Pot Plant Generally the perception of a potted plant has a tapered pot, a stem and leaves. However, due to the fact that Kelvin has to be gender neutral, and older people tend to have a conservative conception of gender rolls (see research report), the flower element was eliminated.


The results: Most people perceived pots to have a tapered edge 6 out of 16 participants drew flowering plants 10 had distinct stems 14 drew plants with leaves Participants from Hong Kong drew bigger leaves (Might be due to familiarity with tropical plants) 27

Participants from Brighton


Participants from Hong KonG


The Birth of the new form factor Taking the semiotics into consideration, the new design was modelled with plasticine, the idea is the leaves would move up and down.


Now back to getting it to work... The next few pages are an attempt to get the leaves to go up and down using gravity as the primary downward force.

Where: Mg is gravity R is the resultant force generated by the SMP CoG is centre of gravity d is distance from the pivot point


The Sad Truth: After more experiments with SMPs it was pretty obvious that the SMPs from America would not be able to push even a light leaf up. The test was done by sandwiching the strip between two pieces of masking tape and placing the SMP sandwich into a pot of warm water above the activation temperature. The result was no deformation at all, the strip could not move the masking tape, thus ruling out the feasibility of using SMPs.


Part three: Third time lucky Throughout the long and winding search for shape changing materials, there had been a back-up plan of using sensors and mechanics to move the part. This was put to the back burner because the previous ones could potentially lead to a more elegant solution, but with the clock ticking and the deadline slowly creeping closer, it was time to look at trying to put plan B in action. 40

Temperature Sensor


Linear actuator


Rubber tubing

First Concept: Pneumatics Pressure causes the tube to straighten

Leaves move up

The idea was to have a closed system of flexible tubing and a syringe. When the syringe is pressed, the volume decreases and the pressure increases (Boyle’s law) causing the flexible tubes to straighten and the leaves to move up. As the system is closed, when the syringe is pulled back, the volume and pressure decrease, making the tubing sag, and

hence causing the leaves to move back down. The system would be based on an input value from an analogue temperature sensor, when the input is under 18C, the microprocessor would trigger a linear actuator pushing the syringe and moving the leaves up. (see flow diagram if confused)

Second Concept: linear pivot CAM


The Linear CAM system is based on two arms (followers) on a central pivot in the stem (push rod) by using stops on the top and bottom to limit the movement. The stops act a lever which rotates the followers around the pivot point when the push rod is pushed up and down. This means that the driver system (the other bits that make it move) only has to be linear.


The distance between the two stops needs to be 11mm in the model, which is on a 2:1 scale, translating to 5.5mm in the final product. The other dimension taken from this model was the vertical translation of the push rod, which is 25mm at this scale and 12.5mm in real life.

In the third Dimension The next bit was to work out how to translate the stops into 3D, as it would be embedded in the stem, the pushrod and followers could be embedded inside a tube with two slots on the side to allow movement. The sequence in images on the previous page is the process of working out the dimension of the holes.


Drving the CAM The easiest solution is to adapt the pneumatics idea and use a linear actuator to push the rod, a small actuator would be chosen to fit in the pot and a lever to augment the distance. As the lever reverses the push pull action, when the temperature drops, the leaves need to go up, and

the CAM system would be pulled down, which means the actuator would have to push. However most actuators small enough to fit inside the pot of the plant have really abrupt movements, which would make Kelvin’s movement super jerky and not plant like.

Pushrod and followers


Solenoid actuator

Pushrod and followers


Another way would be to adapt a wine opener’s rack and pinion lever. Ridges would be cut along the base of the push rod to turn the rotational force into a linear movement. As the load is not large, one gear would be able to drive the system. This system was then adapted for the final design. (Don’t worry, it’s on the next page)



Adpated system The adapted system still uses motors and gears, but a different way to convert the rotational force of the motor to a linear motion is used. The main principal is derived from the simple nut and bolt system, if the nut rotates clockwise, the bot will move downwards and

Motor anticlockwise


Gear 1 anticlockwise

vice versa. In this subassembly the push rod is attached to a threaded rod, and the screw thread of a nut is embedded in a gear, (which we shall call gear 2). The motor is attached to another gear 1 which drives gear 2. As that is quite a confusing paragraph, here’s a diagram:

Thread moves down

Gear 2 and nut clockwise

Leaves move up

With the mechanism finialised,. A CAD model was made to fit into the bounding box speciificed in the PDS.

Initial CAD

The Initial CAD model was used to proportionally model each part to fit PDS dimensions.

The next logical step was to make a model to see if the principal worked. This first prototype didn’t have a motor attached, so gear 1 had to be turned by hand, but it demonstrated the threaded rod moving up and down.


According to the PDS, “1.2 Full range of movement must be made in 3 seconds” So it’s 12.5 mm in 3 seconds, 250mm in a minute A fine pitched M4 thread (fits within the CAD model) has a pitch of 0.5mm (ISO 68:1 1998) 250/0.5= 500 Gear 1 has to turn at 500 rotations per minute (rpm) If both gears have the same number of teeth

Then the motor will have to turn at 500rpm

Tolerances for the threaded rod and gear to allow smooth movement and reduce wear from overuse.

A new problem : The threaded rod rotates. 52

Small motors normally have a high speed and a low torque, to get a small 500rpm motor; there are normally gears to reduce the rotational speed. Gearing a motor down slows its speed, but increases the torque proportionally. A

torque higher than the frictional forces acting on the motor will cause parts to rotate, this means the threaded rod will also rotate. A simple lock and key system was then devised to solve this problem.

Above left: The lock system runs along the threaded rod, but will not interfere with the moving parts. The key is placed on the upper and lower disks holding the gears in place.

Problem Solved Below right: a side view of the lock and key mechanism with the gear sandwiched in the middle; there are 2 keys on the top and bottom to prevent failure.


limit switching

To stop the motor from overshooting and to reduce the size of the microprocessor, limit switches were put in, they work the same way as normal switches, but when they are pushed, it breaks the circuit instead of connecting it; effectively stopping the motor from turning in that direction altogether. It is vital for the limited switches to be 12.5 apart for full range of movement. The switches would be activated by an attachment at the base of the threaded rod. The flow chart on the next page shows the closed loop process for the automation of the product.


Start Take Temperatures Input

5sec delay

5sec delay

Is it under 18C?




Button 1 pressed?

Button 2 pressed?



Motor anticlockwise

Motor clockwise

Button 1 pressed?

Button 2 pressed?


Stop motor




Stop motor


part four: Looking good So now we know that the Kelvin works, the aesthetics and desirability bit needs to be done before user testing can start.


the outer layer has to accommodate the movement of 2 articulating joints and not shear. As Kelvin is based on biomimicry, the first thing that was looked at was how animal joints work as they are pretty good at keeping the inner mechanism in place. In mammals articulating joints are mainly surrounded and held together by soft tissue, so it that option was explored. The task: To look for a material that is soft enough yet flexible. Silicone first came to mind as it used to simulate soft tissue in breast implants. There are many types of silicone, and their flexibility is measured by the Shore hardness scale. For softer materials, the A scale is used: as a guideline, a shore rating of 10 is around the hardness of a gummy bear and a tire tread scores in the 90s. The other factor 58

that needed to be considered was the materials must be hard enough to hold its shape at the other non-articulating parts of the Kelvin. (the top of the stem) So another plan was devised: The inner tube for the CAM system would extend to the tip of the stem will become the “skeleton” of Kelvin, providing structure for the stem and the leaves. It is made of a hard plastic (PP) as it is cheap to produce and can be recycled. Also, it does not have many requirements for stability like the gears or the push rod and followers, so cheap and sustainible was chosen. The outer “skin” of Kelvin could therefore have a lower shore rating and still have structure.

To achieve a desirable finish, a few factors were considered: The colour scheme should evoke feelings of peace and calm, as well as blend in with the home, without being overly obtrusive (which did then come to haunt the usability of the product in a later stage) The next few page will be an image board of the inspiration behind the colour scheme and form factor of the product.




Material Finish/ Tactile desirability With the colour scheme on the left chosen, the finish was left. Silicone has a matt and rubbery finish which increases the user’s tactile satisfaction and gives the product a more premium finish than traditional moulded plastics. As silicone is matt, soft and flexible, the join between the leaves and the stem would be less obvious, increasing the realism of Kelvin, enhancing the overall appeal and desirability of the product. However, after some research a better plastic was found for over moulding the stem and

leaves. TPE (thermoplastic elastomers), they can be injection moulded at a lower temperature than PP, which is required for over moulding) and has good adhesion to PP as a substrate (DeBoer, 2012). It also can be recycled, so although overmoulds cannot be recycles at the end of life, virgin material is not required for initial production. Another plus is TPE can be produced quickly as it does not require curing. For more information about the design for manufacture considerations and material selection to the brand and number, consult the Supergeek book.   71

Size of leaves/ Psychosocial There were two compelling reasons as to why the leaves are disproportionally larger: Baby Face Bias and usability requirements.

Baby face bias: from Universal Principals of Design, Lindwell et al. 2007.

Kelvin is a personified thermometer. (if you haven’t already noticed with the name or read the intro) The size of the leaves are disproportionally larger than plants in nature based on the baby face bias theory: things that resemble younger or immature organisms are seen as “cuter� (Lindwell et al, 2007) ie. Cartoons characters have large head to body ratio and large eyes to resemble babies. Kelvin has larger leaves to resemble plants shoots

which evoke a nurturing response in the user and increasing the impact of Kelvin. Another important reason as to why the leaves should be huge is based on a usability perspective, larger leaves create a larger movement (further away from the pivot) and is more likely to catch the eye of a user. Kelvin is designed to blend in with the environment until needed, so visibility when moving is an very important factor.

The leaf size makes a difference in desirability.

Pot Designs


The baby face bias was also applied to the pot design, although the traditional form of a tapered pot was chosen (Semiotics test, ease of manufacture, blends in with most interiors) the theory was applied to the lip size of the pot. A longer and rounded lip makes the pot makes the “head” of the pot look bigger, similar to a child’s or a puppy’s proportions.

The design to the right was developed to have filleted edges, making the design more organic, in line with the stem and leaves. The original idea was to injection mould the pot out of PP for quicker manufacturing times and the reduce the cost of production; however, after user feedback the material was changed to clay. (see section 5)

Visual PRototypes With all factors considered, the CAD model was finalised and printed for the first visual prototypes. To reduce the print time and supports, the model was sliced in half, but not wisely. The image above is the first print with the model sliced right down the middle producing many supports, damaging the finish on the leaf. The next model (in the front of next

page) was sliced parallel to the x axis, greatly reducing the supports and leaving the top of leaf surface clear. From the models, it obvious that the connection point between the steam and leaves had to be increased to have enough material for movement, the leaves were also thickened as they were very thin.

At this point a major problem was realised: What happens if someone waters this plant like thermometer connected to the 240v mains? The answer was possible death. As this is a very severe problem, everything was dropped to solve the failure mode.


Two methods were used to solve the problem; one was a prevention measure and the other was protecting the user if it happened. The easiest way was just to stick a giant caution label on Kelvin, but that would decrease the aesthetic desirability with a big fat yellow and black sticker. So a more subtle way to warn the user was needed. Mistaking Kelvin for an actual plant would be the main cause of accidental watering, so what tasks would the user have to do to water Kelvin? They would fill up a jug, walk towards it, and water it. Most people would look at the soil whilst watering it The view of the user would be the stem, leaves and the top of the pot. Action was then taken to warn the user that Kelvin is 80

not a real plant. Normal plants are grown in soil so the user would expect to see soil. If the top of the pot was not soil coloured, then it would act as a reminder that Kelvin should not be watered. Measures taken was to limit the damage done if the user waters it. It was decided that the housing and electronics should have an Ingress Protection (IP) rating of 45 (BS 5490:1977, IEC 60529: 1976 Specification for classification degrees of protection provided by enclosures). 4 being “protection against solid objects over 1mm”, and 5: “Protection against low pressure jets of water from all directions”. Rubber gaskets were put into the seals to prevent water damage.

Tolerances of O rings can be found in Supergeek.

The gaskets are placed on the bottom of the stem and around the wire input. O rings are placed around the edges of the 2 plates holding the gears in place and around the top of the pot housing.


Part five: User Testing

The user testing was split into two parts, a study that measures the time taken to notice the change in form of Kelvin, and an in depth interview/feedback session from a carer. Due to time and geographical constraints, the participants were not the direct target user group. However, since Kelvin is a product marketed at carers or families of older people the results still showed a valid insight into future modifications and gave Project Kelvin an insight into the direction of further development.

The Study: Concern: Users would not be able to notice the change in shape. The aim of this study was to answer a few questions regarding usability: How accurately can a person read temperature status? (Effectiveness) How much time does it take for the user to notice the change? (Efficiency) Original methodology: 5 participants will be asked to sit 2m away from a television; a working (movement controlled) prototype of Kelvin will be within peripheral vision. A television show of their choice will be played to the participants. Within the duration of the show Kelvin will move from an open position to a closed position. The time taken for the user to notice will be noted. Rationale: The study simulates the context in which the product is used. As Kelvin was designed to be a product that is only requires the user’s attention when needed, and not one that requires full cognitive concentration, distractions play an important factor in the

usability of the product. This was simulated by the TV in the study. Constraints: The participants recruited in the research phase lived in a care home, and many of them had diminished cognitive ability. From previous feedback sessions it was established that new participants needed to be found for final user testing. Some users were found in Hong Kong (semiotics testing), but there was not enough time to conduct both tests within the timeframe. Another constraint was the prototypes did not have full range of movement. 2 visual prototypes, one of each leaf position were used instead.

The Set up




Adapted Method: As the participants were under 65, further considerations had to be made about participant selection. 3 of 6 participants had glasses or wore corrective lenses, they were asked to remove these to simulate visual deterioration in older people.



LEssons Learnt Results: The time taken varied significantly from not noticing until a break in the video to instantly. This depended greatly on the distraction. In one participant watching the football highlights, he did not notice the change at all as it happened near “an epic goal�. 3 participants all noticed the change instantly, probably due to the large movement created by a person swapping the pots. The other participant did not notice until 2 seconds after the change as they initially thought the movement was because of pictures being taken at the same time Analysis: Although the results varied largely, and is not statically significant, it highlighted the importance of distraction factors in the usability of the product. If the user is quite absorbed in another task, they will not notice the change. Improvements to be made: Kelvin could be advised to be put next to the TV or within field of vision of the living area. As distractions cannot be eliminated, although the user would see the state change during advertisement breaks which happen every 15 minutes. As the leaves are already oversized, increasing its size might add to the load of the followers. Having the bottom of the leaves a different colour would make the movement and change of state more obvious.

Qualitative Most of user centred design is based on the theory that users know what’s good for them and hence should dictate the design of the product. However, sometimes the people that directly interact on a day to day basis with the target user might have a more objective view. A carer agreed to participant in a general feedback session with a “complete honesty” possibility.

The Participant: Cares for a 85 year old female with dementia. Location: Hong Kong Occupation: Dentist/Carer


Findings: It was established that this product would not have much use in tropical climates, but the good news was the carer had lived in the UK for more than 20 years before moving to Hong Kong. She liked the novelty of the idea but was concerned that older people might be a bit apprehensive about product with new technology and should concentrate marketing efforts to younger people purchasing gifts for their parents or grandparents. She

Changes Made: The terracotta pot was adopted and the IP rating could also stand if the inside was sprayed with a waterproof coating. An alert device could be an add-on as it would appeal greatly to families purchasing gifts for older people if they were worried about their safety during the winter months. Due to timing issues this could not be achieved but will be considered for further development of the product. An LED power indicator was put in to show if Kelvin was on. The power button is external, placed on the wire: This will reduce the time for the user searching for the power button and is in a familiar place to older people as it is found on bedside lamps and other appliances.

highlighted the fact that Kelvin’s pot “looked cheap” in plastic; she suggested that it should be made of terracotta or clay for price point specified in the PDS (£40). She also suggested that the product could include some sort of alerting device for friends and family if the house has been left cold for more than a couple of days. It was also pointed out that there is no way of telling if the product is on or off.

Por Por (Chinese for Grandma)


This Is




Further Development If the timescale was infinite for this project, here are the things that could be done: With more funding and time, Kelvin could be made of a shape memory polymer or alloy created specifically for measuring indoor temperatures. This would make the product safer and easier to use (no electrical components), it will also reduce the things that could go wrong by decreasing the number of parts. The CAM and motor system could be simplified to a system without gears. The motor will turn the threaded rod and a nut would move up and down. The upper and lower CAM stops would act as a lever, opening and closing the leaves. A Bluetooth transmitter would be developed to alert friends and family if Kelvin had been left in the cold position for 3 days or more.



Bringslimark, T., Hartig, T., Patil, G.G., 2009. The psychological benefits of indoor plants: A critical review of the experimental literature. Journal of Environmental Psychology, 29(4):422-433 Deboer, D. 2012. TPE/PP overmolded handles: solid feel, soft touch. Medical Design [Online] 12 November. Available at < contract-manufacturing/tpepp-overmolded-handles-solid-feel-soft-touch> Accessed 2 Mar, 2014 Engineering Toolbox, 200?. Coefficients of Linear Thermal Expansion. [online] Available at <> Accessed 1 Feb, 2014. Kanthal, 2008. Thermostatic Bimetal Handbook. Sweden: Kanthal AB. Kellog’s Research Labs, 2012. Discussion on Nitinol. [email] (Personal communication, 12 Feb 2014) Lindwell, W., Holden, K., Butler, J. 2007 Universal Principals of Design. Beverly, MA: Rockport Publishers. Liu, C., Qin, H., Manther, P. 2007 ‘Review of Progress in Shape Memory Polymers’ Journal of Materials Chemistry. 16 (1) Lohr, V. I., Pearson-Mims,C. H., Goodwin, G. K.(1996) ‘Interior Plants May Improve Worker Productivity and Reduce Stress in a Windowless Environment’ Journal of Environment and Horticulture 14(2):97-100 Wilson, E. O. (1984). Biophilia: the human bond with other species. Cambridge: Harvard University Press.


Project Kelvin Progress  

Product development book for Project Kelvin, a form changing thermometer

Project Kelvin Progress  

Product development book for Project Kelvin, a form changing thermometer