Table of Contents
SECTION
PAGE #s
Abstract
p. 3
Introduction
p. 4
Objective
p. 5-7
Our Impact
p. 8-11
Moral Issues
p. 12
Design
p.
Testing Methods
p.
Results
p.
Conclusion
p.
References
p.
Appendix:
p.
A:
Parts List
p.
B:
Circuit Schematics
p.
C:
Mechanical Schematics
p.
D:
Programming Code
p.
1
Abstract
The group was given the task to design a digital health device. In order to complete this task, the
decision was made to create an autonomous thermo-regulation device that can control core body
temperature using thermo-electric coolers (TECs) and microcontrollers. Many of the methods
being used to regulate core body temperature involve using water as a medium or otherwise
unnecessary bulk. This device seeks to achieve thermoregulation by using these TECs placed on
a person’s arm to maximize cooling area and minimize bulk. The preliminary testing and final
results support the design and show that the TECs are capable of reducing core body temperature
as well as temperature on the upper arm, lower arm and fingertips when the TEC is placed on the
underside of the elbow. Though testing results show minimal fluctuation in core body
temperature, the TEC was capable of reducing the temperature of a subject’s fingertips by 7
degrees Celsius.
Introduction
Digital health is a fast evolving field in which technology and healthcare meet to better
human lives. The ES-242: Engineering by Design class at the University of Hartford called upon
a group of engineers-to-be to create a new and innovative product in the Digital Health Field.
The device constucted is a twist to the idea of using cooling to keep swelling from expanding.
The goal of the concept is to be come an Autonomous Thermoregulator Device or ATD. The
ATD would regulate cooling a person’s body without any user input in order to maintain an
optimum health level. The ATD accomplishes this through utilzing Thermo-Electic Coolers
(TECs) which use current to create the a cooling affect. This effect is very similar to the way ice
packs utilize frozen water to create a cooling affect on the body.
The class was required to do extensive research on all angles to accomplish the goal.
Examples of what requirements had to be met were: determine the best location to place TECs,
temperatures that could be harmful to the body, power required to run a full system, and most
importantly determine the required parts that would be in the ATD system. Once these
requirements were met, the group was able to continue moving forward towards a prototype of
the ideal system.
Objective
Controlling core body temperature:
Through external contact we are ultimately trying to regulate core body temperature.
Cooling extremities such as fingers, arms and legs is by far much simpler than cooling the core
of the human body. The human core can be cooled quickly using ice baths and extreme
temperatures but these methods are either bulky or not humanly controllable. Small devices such
as ice packs usually do not work on a large scale to the point where it cools the core body
2
temperature simply because it is too small to affect the body. Also the human body reacts to
cold temperatures by contracting and pulling blood away from extremities to regulate the
temperature of the core. Therefore small systems such as ice packs lose their effect before the
core temperature can be changed. With our Thermo-Electrically Cooled system we are trying to
use the flow of blood to help us with the cooling of the core body temperature. By placing our
system on major arteries and areas with a large amount of blood flow we are trying to use the
circulation of blood to help distribute the cooling throughout the body and ultimately to cool
down the core temperature. Most of the cooling will be concentrated in the area of placement of
the device which is the reason why we will need multiple devices to spread the cooling to a
larger surface area for a greater effect and for quicker cooling of the core temperature. Unlike
other systems, this device is controllable. The output of the device can be altered depending on
how much cooling is desired. Also the system is able to cool for an extended period of time
depending on the source providing power to the system. As long as there is power going into
the system it’s able to cool allowing it to be used to induce controlled hypothermia for extended
periods of time.
Reasons for wanting to control it:
The reason we want to have varying control on our autonomous thermo-regulatory device
is so that it can be used for many applications. We do not only want to be able to regulate the
ATD but we want it to be self regulating depending on the temperature of the body at different
locations along with the allowable temperatures of the system itself. In other words, we also
don’t want the device to operate at excessive temperatures which may become harmful to the
body. Through various temperature sensors we want to both regulate the power output of the
TECs, as well as verify that the device is working properly and doesn’t become dangerous to the
user.
Controlled cooling and heating can be widely applied in medicine, physical activities, bodytemperature sustainability. Sports medicine uses cooling to prevent further injury on muscles
and to stop pain. Heat on the other hand is used to help repair muscle quicker and to relax. This
device could also be used to warm up the body of an athlete before rigorous activities to prevent
injury, and muscle strains. A slow, controlled warming of the body by a few degrees will help
the athlete be ready to perform their best. In the ideal design if the system becomes small
enough to be completely wearable, light, and flexible the device could be worn under clothes to
cool and regulate the temperature of the body while performing physical activities. Keeping the
body from overheating during physical activities will give the individual more endurance and
sustainability. Soldiers could use this device in battle to have more endurance and to prevent
fatigue. In extreme weather, whether hot or cold, this device could be used by people for many
uses. Subarctic researchers could handle more extreme temperatures for a longer period of time,
soldiers could sustain extreme temperatures in the heat of battle, and explorers, hikers, and
outdoorsman could use this device for a much more comfortable experience.
Both Hot and Cold applications possible:
Both hot and cold applications are possible with this device. Because the way thermo-eclectic
coolers work, there is a hot and a cold side to every TEC. Heat is extracted from one side
making it cold while the other side heats up to compensate for the temperature difference. The
physics of a TEC’s behavior is explained later in the design of the project.
Why focus on cooling first:
We are focusing on cooling because we found that there is more interest and application with
cooling then heating. This is because cooling therapy is utilized to help prevent trauma and the
3
progression of injuries. Once cooling was completed, it would just be an easy conversion to
figure out and be able to control the heating application of this device. Cooling is slightly harder
of the two options to understand and to apply to the human body, not only because it is fighting
against the body natural temperature but also against the temperature of the surroundings. At
room temperature the cooling is difficult to achieve, but the same problem would come about in
the heating application if in an environment with temperatures well below zero. Instead of heat
exhaustion at room temperature the effort needs to be concentrated on the exhaustion of the cold
air coming off the cold side of the TEC.
Impact
The number of deaths resulting from brain injury is estimated at 52,000 people a year and
275,000 are approximated to be hospitalized. Nearly 75 % of people that have TBI (Traumatic
Brain Injury) are from concussions and other mild forms of TBI. This problem not only affects
health but also effects peoples wallets. “Direct medical costs and indirect costs such as lost
productivity of TBI totaled an estimated $60 billion in the United States in 2000“(statistics) In
statistics reported by the CDC, falls are the leading cause of TBIs and cause TBIs in adults 65
and older and accounts for 61% of their TBIs. Falls account for 50% TBIs in children ages 0-14.
(causes) When you get a concussion it’s due to the violent nature in which your brain is rattled
around in your skull. In a traumatic experience such as this it can cause brain swelling.
Excessive swelling can then cause brain damage or even result in death.
The system that has been developed, an autonomous thermo-regulation device to aid in
controlling an individual's core body temperature using TECs, would greatly impact the statistics
that were briefly mentioned in the beginning of this report. This ATD can be placed on the head
to cool down tissue and effect the brain. Hopefully, the effect would be significant enough to
prevent brain trauma from becoming more severe. The advantage of this device is that it is
supposed to be a light weight, maneuverable, and cost effective solution to help prevent deaths as
mentioned above and to prevent hospitalizations. This device would also reduce health bills,
helping to cut down on the strain of disability cost, including but not limited to: hospital care,
special care due to brain impairment, necessary equipment to help with brain impairment, lost
wages, physical therapy, funereal cost and etc.
Other then the use in traumatic brain injuries this device can be used for other medical
applications as well. Through this thermo-electrically regulated device we will ultimately be
able to regulate human core body temperature to a safe temperature either above or below the
healthy human body temperature. This application could be widely used in many sports to
regulate the temperature of athletes, applying either to their core body temperature or to the
temperature of an injured body part. This device will be used to prevent injuries with the
possibility to warm and cool the human body to help prevent injuries and restrict the injuries that
occur from getting worse. This device could ideally be used by professional and amateur
athletes as a device that will be portable, light, and self adjusting.
The application of this system could first be used on soldiers to be tested in the roughest
and most extreme conditions. Soldiers could use this device as a way to regulate their
temperature in the harshest of weather so they could sustain more extreme temperatures in the
heat of battle. Also along with core temperature regulation they could use this device for bodily
4
injuries and brain injuries to retard inflammation and swelling on injured body parts. This will
maximize recovery time for soldiers whose occupation is dependant on their mobility.
The autonomous thermo-regulation device will most likely be desirable in small places
such as ambulances. It would be ideal in those close quarters, where there is no room for larger
machines that could be used to cool the body. Our small device could be placed near the area of
trauma to preserve body tissue in large injuries or to reduce swelling in smaller or internal
injuries.
The first design will be somewhat costly to manufacture due to design flaws, accidents,
reworking of design, and the purchasing of equipment and tools. After the final design has been
confirmed and the prototype has been made, the physical design and programming will be easily
reproducible. This should allow for a working system to be built quickly and in an affordable
manner. The self regulated TEC device should be affordable for all hospitals and be able to be
purchased by the average American.
The final device will be extremely safe, it will be encased in plastic, rubber, and
completely insulated. No wires or power source will have contact with the body. Therefore it
will be very unlikely that a user could be electrically shocked by this device. If by any reason
the device malfunctions and is broken to where the internal components are exposed, there will
be a cutoff switch that will shut down any power to the system.
At this point in time, there are no known negative health side effects associated with the
operation of this device. The only precaution that will strictly need to be followed is: when not
under direct supervision, the device should not be in the same location on the body for more than
thirty minutes. External skin damage might occur if precautions are not followed. The design
does not target any extremely sensitive areas; therefore no instantaneous damage will be
possible. In the possibility of malfunction or overheating the system will be programmed to cut
all power to the TEC and continue running the fan to remove heat from the TEC. This will
prevent skin damage from extreme heat in the problem area.
The autonomous thermo-regulatory device doesn’t break any social ethical
responsibilities. However it may violate some professional ethics if the device is used by
professional athletes. The athletes my utilize it while performing their sport to gain more
endurance and to reduce fatigue. This would be unethical because it could extend the natural
abilities of the athlete. An opponent who chooses not to utilize the device would then be at a loss
against someone who does. This imbalance between competitors may create an ethical choice to
be decided in the future world of sports.
Design
The ATD made use of Thermoelectric Coolers (TECs), an Arduino Board, Dallas
Temperature Sensors, Mosfet switches, and heatsinks with fans. To begin, a look at the TEC
shows there are essentially two metal plates connected together, and when a current is run
between them, the TEC can produce heat on one side, and cold on another side, an affect known
as the peltier effect. With the cold side of the TEC is attached to the individual, the heat will
escape through the heat sink and removed by the fan. Should the current ever be switched, the
surface that was once cold will become hot and the surface that was once hot will become cold.
5
Figure C.2 A thermoelectric device’s schematic showing the way heat is absorbed and rejected;
taken from http://en.wikipedia.org/wiki/File:Thermoelectric_Cooler_Diagram.svg.
IR picture of a the cold side of a thermoelectric cooler as contrasted against the hand and
body temperature.
6
The TEC chosen was the TEC1-12705 Thermoelectric Peltier Cooler from Crazyconn (Part
number 22 in Appendix B). Prior to this selection a round TEC with a 66V source was
considered but price became an issue. Therein came the square TEC which operates at 77W that
came from Crazyconn. It allowed the greatest surface coverage to maximize skin contact that
gave the best results. One of the benefits of this TEC include the requirement of only 12 volts to
operate it while it will provide 77 watts of power. Originally, the round TEC idea had a lower
operating voltage so therefore it wouldn’t cool as quickly. This square TEC became more
powerful and was able to reach deeper layers of the skin at faster rates than the previous TEC
choice. The TEC is given a constant amount of power, but is controlled through the combination
of the Arduino and the Mosfet as to how much cooling or heating it will give to the body.
The Arduino is the main work horse in that it controls the whole operation of the system.
All the coding went to this microcontroller which autonomously told the system what to do
depending on temperature readings. Arduino boards come in all shapes and sizes, but for this
particular concept the Arduino Lilypad best suited. It is a small, light and thin micro controller
that doesn’t add much bulk but performs the necessary tasks when programed. At the same time,
should we choose to apply this board directly to clothing, it is completly possible as it has the
necessary holes to allow it to be sewed onto clothing. On the board itself, there are 14 pins, with
6 of them being pulse width modulation. The use of the Pulse width is such that we can control
how often something is running. For example, the TEC is to only be on for only 50% of the time,
then we would set the pulse Width for that particular pin to which the TEC is coordinated with to
only run 50% of the time. In effect the pin is a variable on/off switch. There is also a set of pins
which go to a break-out board to allow connections to the computer via micro-usb ports or to
allow an external power supply. A diagram of the Arduino Board is bellow:
http://arduino.cc/en/Main/ArduinoBoardLilyPad
The micro controller reads in the temperature of the interface between the user and the
device and adjusts the output to the TEC accordingly. This is controlled partly through a
7
component called a mosfet. A mosfet is an electronic switch triggered by a voltage. when
voltage is input to the mosfet it allows a current to flow from one side to the other. If no voltage
is put through then there is no current running through to the output.
The mosfet switches are turning on and off at a rate dependant upon the temperature
reading. The mosfets are the interface used to control the connection between the micro
controller the TEC and the power source. In this situation a temperature is read in, should that
reading be too high then a pulse wave is sent out of the arduino to the mosfet at a fast rate, this
allows the power to flow from the power source to the TEC.
As for the temperature sensors, the design had a flip flop on which sensor to choose from the
list. Primary stages of the ATD had the choice to use the LM34 Temperature sensors since they
were able to run individually. This individuality caused the LM34s to become too bulky for the
ATD and was scrapped for the Dallas Sensors. Below is a picture of the LM34 sensor.
http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/CategoryID/49/List/0/S
ortField/0/Level/a/ProductID/87/Default.aspx
The big design issue that this creates when creating a small device is the number of wires
required to have it become operational. Therein came the Dallas Temperature sensors. which
solved this problem. The requirements of the Dallas connections call for a lower number of
wires, this in turn will help clean up the number of outputs coming from the micro controller.
However this simplicity in hardware caused a complexity in software. This can be seen in the
code below.
Behind this simplified wire scheme, the code for the Arduino must know how to communicate
with the design. This means reading in the unique 8 bit address assigned to each Dallas
temperature sensor, saving that specific temperature reading and converting it to a common
scale(Celsius) for output.
Following the diagram below, we are able to achieve our goal of a “parasite connection”
with the Dallas Temperature Sensors, which allows to have as many sensors as we want. This in
turn will give more temperature readings, however the downside is that with each sensor added
there is a delay in the amount of time it takes to get a reading.
For a parasite hookup to work a power source is connected to the data wire through a
resistor. This data wire is connected in series to the middle pin on each sensor within the
8
parasite connection. There is also a common ground that is connected in series to every sensor
within the parasite connection. This can be seen in the figure below.
http://www.google.com/imgres?imgurl=http://www.strangeparty.com/wordpress/uploads/2010/1
2/DS18B20.png&imgrefurl=http://www.strangeparty.com/2010/12/13/arduino-1-wiretemperaturesensors/&usg=__lTAYs0efYz5U7k4oqhJF6Dn9ajQ=&h=250&w=500&sz=15&hl=en&start=0
&zoom=1&tbnid=tCup0qEORWL4lM:&tbnh=122&tbnw=244&ei=6Fe6TdOjEubs0gHFt4HGA
Q&prev=/search%3Fq%3DDallas%2BTemperature%2Bsensor%2Bparasite%2Bconnection%26
um%3D1%26hl%3Den%26rlz%3D1C1SKPC_enUS410US410%26biw%3D1064%26bih%3D7
48%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=406&vpy=117&dur=4042&hovh=159&hov
w=318&tx=168&ty=94&page=1&ndsp=20&ved=1t:429,r:2,s:0
http://www.google.com/imgres?imgurl=http://www.retorte.ch/public/arduino_temperature_sens
or/maxim_ds18b20.png&imgrefurl=http://www.retorte.ch/tools/experiments_and_snippets/ardui
no_temperature_sensor/&usg=__Q1fEmSGsdVIcRMWH8mHk4PdnY84=&h=98&w=370&sz=
8&hl=en&start=40&zoom=1&tbnid=cv6QwMZZzEHpJM:&tbnh=51&tbnw=192&ei=Y1a6Tc
DcDczegQfevezODw&prev=/search%3Fq%3DDallas%2BTemperature%2Bsensor%26hl%3De
n%26rlz%3D1C1SKPC_enUS410US410%26biw%3D1064%26bih%3D748%26site%3Dsearch
%26tbm%3Disch0%2C1562&um=1&itbs=1&iact=hc&vpx=317&vpy=154&dur=413&hovh=5
2&hovw=196&tx=94&ty=23&page=3&ndsp=20&ved=1t:429,r:11,s:40&biw=1064&bih=748
Schematic of our Whole Circuit
The diagram below shows up our circuit is all connected as previously explained in each
section. The 14.7V power supply connects directly to the two TECs in parallel. In
parallel with those as well is two 12V regulators which are each connected to a CPU
9
fan. These fans and TECs are each connected to their own MOSFET which is
connected to ground. The Mosfets are connected to the "Pulse Width Modulation" ports
on the arduino as well in order to regulate them. There is also the Arduino power supply
which is connected only to the Arduino and ground. The last component is the
temperature sensors. These are powered by the Arduino. These are also connected to
a digital input port on the Arduino lilypad so it can read the digital temperature readings
that they output as well. Due to the large number of components, there are a lot of wires
which may look confusing on a diagram of the whole circuit setup.
Controller sitting on the vacuum table, in process… Notice mosfets wrapped in rubber
bands.
10
Controller wrapped in a compact form. Notice the mosfe-to-power grounds have not been
connected yet…
The peltier device is held in a PVC casing. In addition to providing hosing for the thermoelectric,
fan, heat sink, and temperature sensors it provides for the three following actions imperative to
the success of this idea:
-Heat removal (ducting)
-Hot side/ Cold side separation
-Compression
The heat sink is "attached" with a high performance, silver based thermal paste with a high rate
of heat transfer. Any form of permanent attachment to the heat sink must be conscientious of
the fact that interfering or introducing other epoxy or super glue material will have an effect,
most likely negative, on the heat transfer characteristic between the ceramic surface of the hot
side and the metal body of heat sink. Even in small drops of glue placed at all corners hardened
and expanded increasing the amount of space between the heat sink and hot side surface. The
PVC armature allows us just to use the thermal paste without any form of permanent or
externally based attachment. Attached to the top of the heat sink is a fan. The means of
attachment is super glue. Blue and red LEDs are super glued to the side of the fan. A
temperature sensor is super glued as close as possible to the base of the heat sink so as to
minimize intrinsic error of the bulk temperature sensors we used, see Immersion Sensors vs
Topical Sensors*.
11
Heat Removal (ducting)
*Ducting can be accomplished using aluminum flashing and bending it with a bending tool. See
glossary for the stencil that will yield the dimensions of a duct perfect for a 40mm by 40mm
thermoelectric and heatsink. Notice the DS18B20 fitted on the corner of the fan to measure air
intake temperature. The white wire is a fan speed sensor that is intended for a computer mother
board. Reasonably information could be collected from this wire to a microcontroller. This could
be relevant to objects entering the fan and stopping the blade, i.e. hair or a finger. Designing in
a short amount of time modifications must remain relevant to the time imperative completion
objective of the device.
12
*The above shows a base armature design that was later scrapped because it presented
difficulties when vacuum forming and overall, was more labour intensive to make than the PVC
housing - as recommended by Enver O.
13
*Aluminum foil, exacto knife used to cut it, and the base cut out pictured on the right side. This
base is a high impact resin, heat transfer characteristic of the base is unknown however plastic
is commonly considered an insulator.
Hot side/ cold side separation is important because our objective is to make the device pull heat
out of the body. if these systems are crossed, rate of tissue cooling would be drastically
lowered. If the case did not provide this separation, hot air that is blown off of the heat sink will
waft over the body area we are trying to cool resulting in useless cyclical operation.
14
A more permanent arrangement of all these internal components: heat sink, fan and sensors
could be made by milling a custom plastic case in the milling machine.
This PVC armature with all included internal components is then drapped in hot plastic through
the vacuum forming process. This is more art than process and resulted in multiple issues, see
Vacuum Forming*.
PVC Casing
15
16
Small movement will occur between the heat sink and the surface of the peltier device until the
thermal compound has completely dried and solidified. At this point it is likely that the heat
transfer characteristic will as well be affected negatively and the ability of the heat sink and fan
to remove heat will drop off, though by how much is undetermined. For now the PVC allows
small movement while protecting these internal components from large impact. Though in a
large impact such as dropping it from a table, the heat sink will likely detach from the hot side
surface.
Testing Methods
As Arduino is open source there are some libraries that are distributed for others to tweak
and share as they see so fit, one such library used was the Dallas Temperature library. This
library allowed information to be obtained from each sensor, information like the address and
data output from each sensor were vital to the parasite connections efficiency. As the end design
of our overall project is ever changing the need for more or less temperature sensors changes as
well. The code used is easily adaptable to the change in number of sensors used. So as the
project grows and takes form there is not much work needed in the end to adjust to the new
physical set up of the hardware.
Due to the fact that the Dallas Temperature Library was not our original work the exact
implementation was vague. The documentations written by the creators became very helpful.
References through Arduino website proved to be useful as well.
Code Explained
Below, is have a screenshot of the working code gathering temperature readings from two sets of
smaller systems.
17
18
As stated in the design, the final product has one micro controller(Arduino) controlling a
left and right side. both sides consist of two TECs and various temperature sensors. The
software is designed to complement the hardware design. There are several temperature sensors
on each system, each recording something different and specific. There is a sensor reading
temperature for the heatsink to prevent damage to the device. Temperature is read in from the
TEC to ensure that it is operating as intended. Temperature is read in from the interface between
the TEC and the user’s skin to prevent frostbite or other damage to the user. Each of these
temperature readings are recorded and processed to ensure that these components are running
within a specified range. Should any of these components operate outside the specified
temperature range the entire device will either shut off or adjust its output until it is operating
properly again.
Controlling our MOSFETs
The mosfet, as mentioned previously in the design section is the main switch for the
TEC. Due to the fact that the TEC is not controlled directly from the micro controller to the TEC
there is no code for TEC control, per say. Instead there is a code written to control the pulse
wave output to the mosfets.
Below is a section of the code which controls the mosfet with our predetermined equations along
with an on/off button which is coded in as the pressure sensor.
19
Pressure Sensor controlling TEC and Fan
Fans and TECs being set to values
First the pressure sensor is read to determine whether there is a force applied or not.
Pressure is an indication that the device is properly connected to the user and is in use, an
absence of pressure indicates that the user is wearing the device improperly or the device is not
in use at all. If pressure is applied then we cycle through the rest of the code reading in
temperatures from specific sensors. This temperature reading is processed, from here the micro
controller determines how fast the pulse wave should be output to the mosfet switch. The
20
mosfet is then activated at said rate and power is driven to the TEC. As more temperature
readings are coming in the output pulse speed is adjusted accordingly to maintain safe use. As
interface temperature rises mosfet switches faster, as temperature lowers mosfet switches
slower. This ratio of temperature to mosfet switch speed is predetermined through a specific
equation that takes in the converted temperature reading and outputs the speed at which the
pulse wave should operate.
Finally, we have our fans that work directly on the TECs. as said earlier these are
indirectly controlled from the micro controller via the mosfet switches.
Originally the fans were to operate at full while the device was operating and run for an extra ten
seconds after the device has been shut off. However this proved to be a waste of energy and
inefficient. Instead the fan operated dependant upon the temperature reading of the heatsink.
The hotter the heatsink was the faster the fan would run the cooler the heatsink got the slower
the fan would run. By having the fan idle when not needed we can save power drawn from the
battery, giving the device longer operation time. This control can be seen in the code below.
The operation of the TEC is similar to that of the fan. As temperature rises work harder as
temperature cools work less, however the ideology and reasoning is different. The fan was
slowed down to preserve battery life and efficiency, the TEC is slowed down due to safety
reasons. The TECs could have been run while the temperature is above a certain range and shut
off when below a certain range but this is inefficient and gives a very broad spectrum. With the
use of pulse wave module and mosfet switches the device is able to better control the
temperature output, ensuring that it operates within the specified, predetermined range.
The code was pieced together by calling the various methods, each method controls a
unique component. After one component’s method is called its output is then used as an input to
another component’s method. This can be seen in the flow chart below.
21
Appendix C contains the reference code used to learn how to code the device in part A and the
full functional code in part B.
Utilizing Code and hardware, a full on test was created:
Water Interface Test
22
At the end of this test which lasted approximately 10 minutes and 30 seconds the testers
right middle finger registered a temperature of 32.4 degrees whereas the tester’s left middle
finger measured a temperature of 27.6 degrees Celsius. The larger slopes indicative of a greater
rate of change are seen at the beginning of this test and at the end of this test. This data would
have been more beneficial in terms of yielding insight into the feasibility of the water interface
had the TEC been at maximum operation for the duration of the test.
To do the testing, a power supply was needed. During prelimary test of the device, a bulkier
powersupply than the desired option was utilized. The figure below is that of BK precision. With
this device, and our system set up, different voltage and current options were allowed to be
23
tested to see just how the TECs and Fans respond. A device like this began to shape the concept
as it could reveal what appropriate voltages and currents should be applied onto the end result
system.
Once the given requirements of the Arduino board, TECs and Fans were in place, the portable
solution to the battery needs was created. Below is a figure of what the portable battery pack
may look like. Below the picture itself contains the data for our battery that was chosen.
Average Power Consumption Estimation
TECs Fans
Voltage Sent
14.7V 12V
Duty Cycle
50% 100%
Average Voltage Consumed 7.35V 12V
Average Current
2.0A 0.7A
Multiplied by 2 for each
4.0A 1.4A
component
With the given data, calculations were done on the battery life of a system:
Maximum mAh used in one hour = 4.0A + 1.4A = 5.4A Equation to determine how long
this battery will last:c5400mAh / 60mins = 4400mAh / battery life Battery Life = 48.88mins.”
24
Results
Data and Analysis
25
Water Interface
40
Finger Temperature
35
30
31.8
30.2
30.8
27.2
25
32.2
28.6
31.8
28.6
32.4
33.4
27.6
27.8
32
31.8
32.6
31.8
31.6
31.2
31.4
26.6
26.6
26.4
25.8
25.2
25.8
25.6
20
15
10
5
0
31.8
30.8
32.2
31.8
32.4
33.4
32
31.8
32.6
31.8
31.6
31.2
31.4
TEC Power
Observing the graph, the power sent to the TEC was gradually increased over a time span
of 10:30s. However what this test does provide is evidence towards the feasibility of a water
interface medium which would increase the effective interface surface area of the TEC and allow
it to permanently operate at maximum potential. Increasing interface surface area has the
potential to increase overall rate of bodily heat removal. Importantly, this test highlights the
slow response characteristic of a water interface medium.
26
Multi-Point Water Interface Test
*Note the size of this water interface. A water interface with this mass of water would not be able to cool
efficiently with regards to time. The water interface pouch used in this test contained approximately 34
grams of water and is pictured in the previous photo.
27
Multi-Point Water Interface Test
40
35
Degrees Centigrade
30
25
20
15
10
5
0
0
1
2
4
5
7
9
11
13
15
17
19
21
24
27
31
Core Temp
34.2 34.2 35 34.8 35
Upper Arm Temp
31.8 30.8 32.2 31.8 32.4 33.4 32 31.8 32.6 31.8 31.6 31.2 31.4 31.6 31.8 31
Lower Arm Temp
Interface Temp
36 34.4 34
31 31.2 31.4 32.2 32.4 33
35 34.6 34.4 34.4 33.8 34.8 34.4 34.2
32 31.8 32.6 32.4 31.8 31.6 31.8 31.6 31.4 31.2
30.2 27.2 28.6 28.6 27.6 27.8 26.6 26.6 26.4 25.8 25.2 25.8 25.6 25.6 25.2 24.6
Middle Finger Temp 29.2 28.6 29.6 29.2 28.8 28.8 28.8 27.2 27 26.6 26
25 24.8 24.8 24.2 23.6
This is the capstone test of this project bearing evidence of its function and ability to reduce the
temperature of the body. Just one TEC was responsible for the cooling observed in the interface
temperature readings as well as the middle finger temperature readings seen above. In this test the TEC
was placed just above the brachial artery at a compression level of greater than .22 lbs. The Dynatron
DF124028_U Fans ran at 12 volts and 52 milliamps and the TEC was run at 9 volts and 3.07 amps. A
water interface pouch weighing ***grams was placed in-between the cold surface of the TEC and the
tester’s skin. Temperature was recorded using the Infrared Pocket Thermometer from Radioshack. The
water interface pouch was at room temperature at the start of this experiment.
Temperature was taken at the exact same location for each of the 5 locations listed above. Core
temperature was measured just under the neck, upper arm temperature was measured just above the
bicep, lower arm was taken below the module on the outside of the arm, interface temperature was taken
28
through a small hole on the top of the arm band and lastly middle finger temperature was taken at the tip
of the right hand middle finger.
The same small pouch of water that was used in the previous water interface test was used in the MultiPoint Water Interface Test. The interface temperature reading was affected by the warm evacuation side
of the module, so the data appears with this systematic error. When the device was taken off at the end of
the test, the temperature of the bag was immediately recorded at 14.2 degrees C and the area of skin
underneath the bag registered topically at 17.6 degrees C. A 14.2 degree C contact surface is well
outside the range that might induce injury, 3-4 degrees C 1 Chulalongkorn University.
Though the device is powerful enough for immediate local cooling without the water pouch, it is apparent
that one TEC with a water pouch was not enough to significantly impact cooling of the upper arm or core
body temperature when considering the body’s homeostatic ability as well as the directional flow of the
blood in the arteries on which the TEC was positioned directly above. If tested over a longer period of
time, without the water interface and if test readings were taken in different locations relative to the
underlying blood vessels and not over muscle tissue as they were, the rate of heat transfer would be
greater and likely more evident in upper body locations. As the device sat on a blood vessel (brachial)
that was delivering oxygenated blood to the hand, the results of the loss of heat in the tester’s right hand
was within predictions. The final two temperature readings of the right hand middle finger were 24.2,
23.6 degrees C and the corresponding temperatures on the left hand middle finger were 29.2 and 29.8
degrees C.
Also given the results of the previous water interface test, it is likely that the water pouch impacted the
rate of cooling negatively and significantly, however it was deemed proper in the case of prevent injuring
and increasing comfort for the tester for the duration of the 30 minute test cycle.
In conclusion one TEC when run at the maximum respective of the capability of our hardware and
interfaced with a water pouch, placed at the brachial artery of the right arm of a 21 year, old male, 160lb
1
Prawit Janwantanakul, Department of Physical Therapy, Faculty of Allied Health Sciences, Chulalongkorn
University
29
tester was capable of cooling the tester’s middle finger at a distance of approximately 30 inches from the
test location on the testers brachial artery by at least 5.7 degrees C.
Conclusion
In the end, the ES242 worked to obtain a proof-of-concept of an ATD which would
advance the Digital Health field. The class worked to find proper calculations for a desired
device to which it then obtained the parts which would fill the calculations best. Once these parts
were obtained, coding was designed specifically for the product which became a proof-ofconcept. From there, a stepping stone for what this device could ultimately become was born. In
the future, a device like this has a possibility of ending up not only in the medical facilities but
also in the household setting.
Further advancements in this proof-of-concept can be in the locations of housing and
parts. The idea behind housing is how the device is supposed to be worn, attached, or where it is
placed along the body. Different sections of the body are going to have to require different sizes
of the contraption in order to obtain its desired operation. In order to make the device more
usable in all parts of the body, it would have to be smaller and therefore changes to the wire size,
controller size, and casing size would need to be shrunk down to more applicable sizes. A
powerful controller is always a benefit to have when collecting a lot of data and running two sets
of TECs so the current 8mhz chip may not be sufficient for future-proofing the design.
A class as such provided valuable lessons, though given implicitly, for future engineer
fields. As an example, this class allows students to understand just what it may be like to
communicate with other people, although they may be doing different things, each person needs
to be able to coordinate with others as one whole group. This was a valuable simulation of the
possibility of the lives some of the students may live, and therefore important to experience such
events while in an educational scope as apposed to a scope in which jobs and money are on the
line. The results could also be measured in many things such as a responsibility, a new found
importance for respect, and friendship. The growth that took place in terms of being an adult
was immeasurable for some. The ability to sit down and design something together and also
get a result is wonderful, especially because of the lack of direction originally provided. This
project was for students, for young engineers. All of the project failures and successes were
leaned onto the young engineers. Much like the real world there was no safety net, if the
project was not done then the project was not finshed. Any kind of issue pertaining to parts,
labor, or the like was soely vested onto the students who worked on the project. This type of
class taught implicitly just what it means to work on a project as a true engineer. That may well
be the best lesson anyone could learn at such a young age.
30
Appendix A: Works Cited
Works Cited
All-Battery.com - Rechargeable Batteries & Chargers. Web. 09 May 2011. <http://www.allbattery.com/>.
Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & More. Web.
09 May 2011. <http://www.amazon.com/>.
"Answers.com - What Is the Lowest and Highest Tempatures Humans Can Survive under."
WikiAnswers - The Q&A Wiki. Web. 09 May 2011.
<http://wiki.answers.com/Q/What_is_the_lowest_and_highest_tempatures_humans_c
an_survive_under>.
"Arduino - ArduinoBoardLilyPad." Arduino - HomePage. Web. 09 May 2011.
<http://arduino.cc/en/Main/ArduinoBoardLilyPad>.
"Arduino - FAQ." Arduino - HomePage. Web. 09 May 2011. <http://arduino.cc/en/Main/FAQ>.
"Arduino - Software." Arduino - HomePage. Web. 09 May 2011.
<http://arduino.cc/en/Main/Software>.
"Arduino Playground - OneWire." Arduino - HomePage. Web. 09 May 2011.
<http://www.arduino.cc/playground/Learning/OneWire>.
31
"CDC - Injury - TBI - Statistics." Centers for Disease Control and Prevention. Web. 09 May 2011.
<http://www.cdc.gov/traumaticbraininjury/statistics.html>.
"CDC - Injury - TBI - Statistics." Centers for Disease Control and Prevention. Web. 09 May 2011.
<http://www.cdc.gov/TraumaticBrainInjury/statistics.html>.
"Charting Your Basal Body Temperature Information and FAQ - Fertility Plus." FertilityPlus:
Information Written by Patients, for Patients. Web. 09 May 2011.
<http://www.fertilityplus.org/faq/bbt/bbtfaq.html>.
"Digital Humidity Sensor SHT21 - Smallest Humidity Sensor for Demanding Measurements Sensirion AG." Relative Humidity Sensor, Gas Flow Sensor, Mass Flow Sensor and Liquid
Flow Sensor Solutions - Sensirion AG. Web. 09 May 2011.
<http://www.sensirion.com/en/01_humidity_sensors/05_humidity_sensor_sht21/00_h
umidity_sensor_sht21.htm>.
"EFunda: Theory of Thermocouples." EFunda: The Ultimate Online Reference for Engineers.
Web. 09 May 2011.
<http://www.efunda.com/designstandards/sensors/thermocouples/thmcple_theory.cf
m?Orderby=Seebeck0C>.
"FSR, Force Sensing Resistor, Robot Force Sensors, Robot Pressure Sensor, Robot Touch
Sensor." Trossen Robotics - World's Leading Robot Shop for Robot Kits and Robot Parts!
Web. 09 May 2011. <http://www.trossenrobotics.com/store/p/6496-1-5-Inch-ForceSensing-Resistor-FSR-.aspx>.
32
"FSR Sensor Tutorial." Limor. Web. 09 May 2011.
<http://www.ladyada.net/learn/sensors/fsr.html>.
The GNU Operating System. Web. 09 May 2011. <http://www.gnu.org/home.html>.
"Hypothermia." Wikipedia, the Free Encyclopedia. Web. 09 May 2011.
<http://en.wikipedia.org/wiki/Hypothermia>.
"Is Lithium-ion the Ideal Battery? – Battery University." Battery Information from Battery
University. Web. 09 May 2011.
<http://batteryuniversity.com/learn/article/is_lithium_ion_the_ideal_battery>.
"Leah Buechley - LilyPad Arduino - Introduction." MIT Media Lab. Web. 09 May 2011.
<http://web.media.mit.edu/~leah/LilyPad/>.
"Level1 Thermocouple Skin Temperature Sensor, 20/bx." Medical Supplies | Surgical Supplies |
Medical Equipment | Medex Supply. Web. 09 May 2011.
<http://www.medexsupply.com/products/pid47441/Level1ThermocoupleSkinTemperat.htm?zmam=34602484>.
"Medical Emergency." Wikipedia, the Free Encyclopedia. Web. 09 May 2011.
<http://en.wikipedia.org/wiki/Medical_emergency>.
"Model 1672 - Triple Output Quad Display DC Power Supply ((2) 0-32V, 0-3A/(1)5V, 3A) - B&K
Precision." B&K Precision Manufactures a Range of Electronic Test & Measurement
Instruments. Web. 09 May 2011.
33
<http://www.bkprecision.com/products/model/1672/triple-output-quad-display-dcpower-supply-2-0-32v-0-3a-15v-3a.html>.
Number, Part. "Heat Sinks Information on GlobalSpec." GlobalSpec - Engineering Search &
Industrial Supplier Catalogs. Web. 09 May 2011.
<http://www.globalspec.com/LearnMore/Electrical_Electronic_Components/Fans_Elect
ronic_Cooling/Heat_Sinks>.
"OneWire Arduino Library, Connecting 1-wire Devices (DS18S20, Etc) to Teensy." PJRC:
Electronic Projects with Components Available Worldwide. Web. 09 May 2011.
<http://www.pjrc.com/teensy/td_libs_OneWire.html>.
"Parts Needed." Instructables - Make, How To, and DIY. Web. 09 May 2011.
<http://www.instructables.com/id/how-to-Control-arduino-by-bluetooth-from-PCpock/step1/controlling-from-a-terminal-in-windows>.
Piatek, Anton. "Arduino 1-wire Temperature Sensors « Strangeparty." Strangeparty. Web. 09
May 2011. <http://www.strangeparty.com/2010/12/13/arduino-1-wire-temperaturesensors/>.
"Polymer Lithium Ion Battery - 110mAh - SparkFun Electronics." News - SparkFun Electronics.
Web. 09 May 2011. <http://www.sparkfun.com/products/731>.
Retorte.ch – News. Web. 09 May 2011.
<http://www.retorte.ch/public/arduino_temperature_sensor/fetch_temperature.perl>.
34
RobotShop | Robot Store | Robots | Robot Parts | Robot Kits | Robot Toys. Web. 09 May 2011.
<http://www.robotshop.com/>.
Sorin, Trimbitas. "How to Use the DS18S20 and DS18B20 Temperature Sensors with Arduino."
Dedication to DIY and Programming. Web. 09 May 2011.
<http://stuff.nekhbet.ro/2009/08/23/how-to-use-the-ds18s20-and-ds18b20temperature-sensors-with-arduino.html>.
Thermoelectric, Peltier Cooler. Web. 09 May 2011. <http://www.kryotherm.ru/>.
"Under Armour Clothing under Armour Mens Fire Retardant H Www.MidwestHuntersOutlet.com." Hunting, Rifle, Deer Hunting, 22 Rifle, Game
Hunting, Hunting Accessories, Hunting Rifle, Hunting Guns. Web. 09 May 2011.
<http://www.midwesthuntersoutlet.com/item.aspx?PID=386418>.
"Used Temperature Sensor." Bio-medical.com | Products. Web. 09 May 2011. <http://biomedical.com/products/used-temperature-sensor.html>.
WidgetWorks Unlimited. Web. 09 May 2011. <http://www.widgetworksunlimited.com/>.
"WiFly Wireless SpeakJet Server - SparkFun Electronics." News - SparkFun Electronics. Web. 09
May 2011. <http://www.sparkfun.com/tutorials/158>.
35
Appendix B: Parts list
1) Part #and Name-$19.90 - PRT-10217 - LiPo Charger Basic ($9.95 ea.)
Quantity- 2 units
Manufactures-N/a
Vendor-SparkFun
Link to data Sheet-http://www.sparkfun.com/products/10161
Product description -The USB LiPo Charger is a basic charging circuit that allows you to charge 3.7V LiPo cells at
a rate of 500mA or 100mA per hour. It is designed to charge single-cell Li-Ion or Li-Polymer batteries.
2)Part #and Name- $11.85 - PRT-09771 - Theragrip Thermal Tape ($3.95 ea.)
Quantity- 3 units
Manufactures-N/a
Vendor-SparkFun
Link to data Sheet-http://www.sparkfun.com/products/10161
Product description- Thermalloy Theragrip is a double sided tape for ceramic or metal heatsink packages.
Theragrip provides both good thermal performance and excellent electrical isolation.
3)Part #and Name-$11.85 - COM-10256 - MOSFET Power Control Kit ($3.95 ea.)
Quantity- 3 units
Manufactures-N/a
Vendor-SparkFun
Link to data Sheet-http://www.sparkfun.com/products/10161
Product description- -This MOSFET power control kit is basically a breakout for RFP30N06LE which is a very
common MOSFET with very low on-resistance and a control voltage (aka gate voltage) that is compatible with any
3-5V micro controller or mechanical switch.
4)Part #and Name-$20.85 - PRT-00731 - Polymer Lithium Ion Battery - 110mAh ($6.95 ea.)
Quantity- 3 units
Manufactures-N/a
Vendor-SparkFun
Link to data Sheet-http://www.sparkfun.com/products/731
Product description--This is a very small, extremely light weight batty based on the new Polymer Lithium Ion
chemistry. This is the highest energy density currently in production. Each cells outputs a nominal 3.7V at 110mAh!
Comes terminated with a standard 2-pin JST connector - 2mm spacing between pins.
5)Part #and Name-$44.85 - DEV-08786 - LilyPad LiPower ($14.95 ea.)
Quantity- 3 units
Manufactures-Leah Buechle
Vendor-SparkFun
Link to data Sheet-http://www.sparkfun.com/products/8786
Product description--A small, but very mighty power supply. This board was designed to be as small and
inconspicuous as possible. The nice thing about LiPower is the ability to use rechargable Lithium Polymer batteries.
These batteries are smaller, flatter, and last much longer than a AAA battery. Attach a single cell LiPo battery, flip
36
the power switch, and you will have a 5V supply to power your LilyPad network. Good up to 150mA. Short circuit
protected.
6)Part #and Name -922007094-02 Dynatron DF124028_U 40x40x28MM SLEE (9.78EA Total with S&H =
$34.54)
Quantity- 1 unit
Manufactures- www.dynatron-corp.com/
Vendor- www.compuvest.com/
Link to data Sheet- http://www.dynatron-corp.com/en/product_detail_1.aspx?cv=&id=46&in=0
Reason for purchase -This CPU fan was purchased to be a heat sink for our TECs. It will disperse the heat that
accumulates on it.
7)Part #and Name -67-3AIT-R2BW 12"x12" Vacuum Form Machine ($129.95)
Quantity- 1 unit
Manufactures- http://www.widgetworksunlimited.com/
Vendor- http://www.amazon.com/
Link to data Sheet- http://www.widgetworksunlimited.com/12_x12_Hobby_Vacuum_Former_p/vf-12x12vac_former.htm
Reason for purchase -This vacuum form machine was purchase to serve as a means to assemble the fans and TECs
together as one component.
8)Part #and Name – COM-10256 MOSFET Power Control Kit (3.95)
Quantity - 3 units
Manufactures- N/A
Vendor- http://www.sparkfun.com/
Link to data Sheet- http://www.sparkfun.com/datasheets/Components/General/MOSFET-Power-Control-v10.pdf
Reason for purchase -This Mosfet is used as a switch by the lilypad to regulate the power flowing to the TECs and
Heat Sinks.
9)Part #and Name -DEV-08786 Lilypad LiPower($14.95)
Quantity - 3 units
Manufactures- http://www.arduino.cc/en/Main/ArduinoBoardLilyPad
Vendor- http://www.sparkfun.com/
Link to data Sheet- http://www.sparkfun.com/datasheets/DevTools/LilyPad/LilyPad-PowerSupply-Lipo.pdf
Reason for purchase -This device is built to function as a 5V power supply to the lilypad microcontroller when
connected to a battery.
10)Part #and Name -DEV-09266 Lilypad Arduino 328 Main Board ($21.95)
Quantity - 3 units
Manufactures- http://www.arduino.cc/en/Main/ArduinoBoardLilyPad
Vendor- http://www.sparkfun.com/
Link to data Sheet- http://www.atmel.com/dyn/resources/prod_documents/8271S.pdf
Reason for purchase – This Lilypad is the microcontroller for our operation. It will read the temperature data and
operate the TECs using the mosfet and code.
11)Part #and Name -DEV-09716 FTDI Basic Breakout 5V ($14.95)
Quantity - 3 units
Manufactures- Leah Buechley and SparkFun Electronics
Vendor- http://www.sparkfun.com/
Link to data Sheet- http://www.sparkfun.com/datasheets/DevTools/Arduino/FTDI%20Basic-v21-5V.pdf
Reason for purchase -This breakout board helps supply the battery power to the lilypad and has indication LEDs to
show whether it is operational.
12)Part #and Name -PRT-00731 Polymer Lithium Ion Battery – 110mAh ($6.95)
Quantity - 3 units
37
Manufactures- N/A
Vendor- http://www.sparkfun.com/
Link to data Sheet- http://www.sparkfun.com/datasheets/Batteries/UnionBattery-110mAh.pdf
Reason for purchase -This is the 3.7V power supply for the lilypad which is raised to 5v by the breakout.
13)Part #and Name -SEN-00245 One Wire Digital Temp Sensor ($4.25)
Quantity - 8 units
Manufactures- http://www.maxim-ic.com/
Vendor- http://www.sparkfun.com/
Link to data Sheet- http://datasheets.maxim-ic.com/en/ds/DS18B20.pdf
Reason for purchase -This is the temperature sensor which will gather data about our targets temp. The data is sent
to the lilypad which uses it to determine when to operate the TECs.
14) Quantity 2 - $29.90
Part #and Name - DEV-10275 - Lilypad FTDI Basic Breakout - 5V ($14.95 ea.)
Vendor- http://www.sparkfun.com/
15) Quantity 1 - $1.95
Part #and Name - PRT-09599 - Heat Sink Compound
Vendor- http://www.sparkfun.com/
16) Quantity 1 - $14.95
Part #and Name - DEV-08937 - LilyPad XBee
Vendor- http://www.sparkfun.com/
17) Quantity 1 - $4.95
Part #and Name - ROB-08449 - Vibration Motor
Vendor- http://www.sparkfun.com/
18) Quantity 4 - $17.00
Part #and Name - SEN-00245 - One Wire Digital Temperature Sensor - DS18B20 ($4.25 ea.)
Vendor- http://www.sparkfun.com/
19) Quantity 4 - $23.80
Part #and Name - SEN-09673 - Force Sensitive Resistor - Small ($5.95 ea.)
Vendor- http://www.sparkfun.com/
20) Quantity 4 - $3.80
Part #and Name - COM-00529 - Super Bright LED - Blue - 1pcs ($0.95 ea.)
Vendor- http://www.sparkfun.com/
21) Quantity 3 - $65.85
Part #and Name - DEV-09266 - LilyPad Arduino 328 Main Board ($21.95 ea.)
Vendor- http://www.sparkfun.com/
22) Quantity 6 - $29.34
Part #and Name - TEC1-12705 Thermoelectric Peltier Cooler 40 mm x 40mm 12V 77 Watt
Vendor- http://www.sawsmiter.com/detail/p_B002UQKEU8/Best-deal-TEC1-12705-ThermoelectricPeltier-Cooler-40-mm-x-40mm-12V-77-Watt-onsale.html
SUBTOTAL COST : $685.90
Shipping/Handling : $24.99+ $14.77
GRAND TOTAL: $725.66
38
Appendix C: Source Code
Below is sample code from the Arduino Playground of the OneWire setup:
Part A)
39
40
Part B)
Below is our Final Code:
41
42
43
44
Appendix D: Circuits Schematic
Appendix E: GNU Open Source
Software used herein is unique to the project. Though it may be a derivative of software published under
the GNU licence, it is code that can only be used with the corresponding mapping that we generate and
therefore has to be modified to fit any other device with different hardware or physical architecture. It is
the unique functional correlation between devices and their respective code that makes this summation of
this device a unique and creative generation of our own. The code that was referenced will be properly
sourced.
The GNU and GPL licence states the following;



The freedom to run the program, for any purpose (freedom 0).
The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the
source code is a precondition for this.
The freedom to redistribute copies so you can help your neighbor (freedom 2).
45

The freedom to improve the program, and release your improvements to the public, so that the whole
community benefits (freedom 3). Access to the source code is a precondition for this.
As cited from http://www.gnu.org/home.html
All Arduino hardware is also open source and claims the following;
Open-source hardware shares much of the principles and approach of free and open-source software.
In particular, we believe that people should be able to study our hardware to understand how it
works, make changes to it, and share those changes. To facilitate this, we release all of the original
design files (Eagle CAD) for the Arduino hardware. These files are licensed under a Creative
Commons Attribution Share-Alike license, which allows for both personal and commercial derivative
works, as long as they credit Arduino and release their designs under the same license.
The Arduino software is also open-source. The source code for the Java environment is released under
the GPL and the C/C++ microcontroller libraries are under the LGPL.
As cited from http://arduino.cc/en/Main/FAQ
46