Soldier Heat Sensor
By: David Dewar, Lauren Gutierrez, Daniil Zolotarev
Engineering Design VI
February 25, 2011
- I pledge my honor that I have abided by the Stevens Honor System
Introduction (Section1 1)
The group decided to pick the soldier heat sensor. The purpose of the heat sensor is to
provide additional safety to soldiers and their units. It will be placed on the back of a soldier
helmet, collar, or book bag and whenever it detected a moving heat trace above a particular
temperature it will alert the soldier in a discrete manner.
As a group we decided to spilt the device into three main components. The three main
components of the device are the sensor, the microprocessor to process the signal and rely a
signal to the soldier, and the output device. Each group member was responsible for researching
a particular part.
Section 2
Sensor:
The project at hand is meant to detect a human body from a distance away. The way this
is done through sensors is with infrared heat sources. Being that there are various different
categories of infrared light (near-infrared, mid-infrared, and long-infrared also known as
thermal-infrared) we must hone in on one of these categories. The key difference between these
types of infrared light, excluding the wavelengths, is that thermal-IR is emitted by an object
instead of reflected off it as in the other two types of infrared light. Thermal-infrared is emitted
because of activity on the atomic level, which is why inanimate objects emit little to no thermalinfrared light. Our project thus must hone in on the thermal infrared light sources. In order to
detect such a light source, there must be a sensor that can measure specific wavelengths
accurately. Knowing the type of infrared light we are trying to measure determines that our
sensor must measure wavelengths measuring from 3 microns to over 30 microns [Infrared
Temperature Measurement Theory and Application, Page 1]. The sensor to be chosen must be
used to create the thermal imaging device which will help to notify the soldier.
There are two different types of thermal-imaging devices, un-cooled and cryogenically
cooled. The cryogenically cooled devices are rather expensive and more prone to damage. These
types of systems have the elements sealed inside a container that cools them to below 32 F.
These types of devices are very accurate and have incredible resolution and sensitivity. A
cryogenically cooled device has the ability to detect as small as 0.2 F temperature changes from
over 1,000 feet away [How Thermal Imaging Works, Page 2]. The other types of thermal
imaging devices are un-cooled. These are most common due to their inexpensive and rather
durable nature. This unit operates at room temperature and has a battery that is built into the unit.
The type of imaging we would want to use is different from the ‘night vision’ that most people
think. Pending on the distance in which our project plans on being accurate, we must choose
between these two different devices.
Our project is primarily focused on targeting individuals who may be trying to flank a
moving unit. This would require a unit with a focal length of 350mm or greater. As seen in the
chart to the right (Camera
Core
Cost
versus
Focal
Length), economically it is
more expensive to create an
un-cooled device with a focal
length above 350mm. This
poses a problem in the design
Reference: Cooled vs Uncooled Devices, Page 2
scheme for our project. As mentioned above, a cooled thermal imaging device is more prone to
damage and is not as durable as the uncooled device. This puts the group in a sticky situation to
decide which type of device we would want to go with. The cooled device would be less
expensive, however would not be durable whereas the uncooled device would be much more
durable, yet less accurate. Choosing which type of device we must go with involve a numerous
amount of conditions and the feasibility to implement into a soldier’s combat gear.
Seeing the various conditions that soldiers combat in, extreme weather temperatures and
all different types of precipitation it makes sense to go with the uncooled system. This poses a
problem when the system is in freezing conditions, because the uncooled system would fail.
These complications pose various different things we must counter to obtain a working product.
The information that is gathered through the thermal imaging device must be sent through a
microprocessor to process the signal and send alerts to the soldier.
Microprocessor
The main computing force of this project should be a microcontroller. In the recent years
microcontrollers have become more prevalent in hobbyist projects. This has resulted in a drop in
costs as well as the development of open source microcontrollers. A look at any hobby and do-ityourself website will show that microcontrollers are being used to perform tasks that once
required complex circuitry. Most importantly these devices are used in the collection and
analysis of data obtained by sensors, which is appropriate for our application.
It would be possible to program a microcontroller using languages we are already
familiar with such as C or C++. Although we have learned how to program a microcontroller in
assembly language the ability to use higher languages makes programming simpler and more
accessible. Writing C code is also much less time consuming compared to assembly language
which requires the programmer to write out every single instruction. The use of compilers such
as GCC or CodeVisionAVR allows for the compiling of C code for an AVR microcontroller. (T.
Fryza).
If, however, the use of assembly language is required in a certain application it is possible
to write a small segment of code in assembly. The compilers mentioned allow for such a
combination of code by using special functions. Should there be a need for very specific
instructions to be written to the microcontroller using only assembly then it is possible using
these instructions.
Microcontrollers are available in large quantities and for very low prices. AVR is
currently one of the major providers of microcontrollers for hobby use, the most famous one
being the arduino. Programmers can be purchased and a compiler can be found for free. This
being an open source microcontroller there are multiple sources of documentation available for
the construction of such a device. One primary source is the hobbyist publication Makezine
which had a whole issue dedicated to the arduino. It is a very flexible platform and is often used
to read sensor data. This device proves to be simple to use and manufacture which should be
useful in its application for this project. Multiple versions are available depending on the
memory usage required. If we are to reduce the number of components that deal with the data
coming from the sensors and leading to the output of this device then an AVR chip with greater
memory can be used along with a code that should handle every task necessary. If we are to
reduce the amount of computing power needed, reducing time between instruction sets then a
lower memory device can be employed with more external components sorting the information
before it even reaches the microcontroller.
Output Device
The purpose of the output device is to notify the solider that the heat sensor has detected
something behind him and that he should proceed with additional caution. There are three
different options for an output device that are currently being considered. A small LED light that
can easily be attached to the soldier’s uniform and would light up when the heat sensor detects
something. A small vibrating motor is an additional option; it could be clipped onto the solider
uniform in the neck area which is a sensitive area so the soldier would not miss the signal. An
additional output device being considered is an ear piece. It would make a particular noise when
the heat sensor detected an object.
A small LED that operates off a remote signal would a very useful output device because
it would be wireless and not produce any noise. A negative aspect of a wireless LED would be it
would require a signal that could be picked up by the enemy therefore, exposing a soldier and his
unit’s location and at night a small light would be very obvious in the dark.
Another output device that could be utilized is a vibrating motor that would alert the
soldier to potential danger when the heat sensor picked up on something. Similar to how cellular
phones vibrate when a signal is being sent to the device is how this output device would work.
The heat sensor would pick up a heat trace and if it was high enough the microprocessor would
then send a signal to the small vibrating motor. A negative aspect of this output device is that the
soldier may not feel the vibrations due to the adrenalin rush he maybe experience from being out
and in harm’s way.
An additional output device that could be used is an ear piece that would make a beeping
noise or give off some type of tone when the heat sensor detected something behind the soldier.
The ear piece would be similar to a blue tooth device. The heat sensor will send a signal when it
has detected something to the ear piece which will then notify the solider. A negative aspect of
using this is the sound the ear piece gives off could potentially be picked up by the enemy,
therefore putting the soldier and his unit in harms way.
Section 3
Sensor:
The sensing system that would be implemented on this system is much simpler than previously
mentioned. When comparing the two types of thermal imaging devices; uncooled vs. cooled
systems; although using a cooled camera could be more cost efficient, that device is simply
impractical. The emphasis on this project is making the product portable, which means that the
sensing units will be driven based on size, weight and power consumption. Being each soldier
has to carry an immense amount of gear, the unit needs to be small and lightweight; yet due to
the weather conditions in which the product must endure, the sensors cannot sacrifice durability.
Being the product must be portable; the sensors thus must use minimal power to be as accurate
as possible. Having these conditions to meet, make selection of the sensing units the driving
force in this project.
The first and main sensing unit that must be selected for our project needs is a long wave
infrared (LWIR) detector. As mentioned before, the project calls for uncooled devices, therefore
all the sensors must be uncooled. The type of
LWIR detector that could be considered would be
a microbolometer; cross section seen at the right.
A microbolometer is an array of tiny heat detecting
sensors that are sensitive to infrared radiation from
7 to 14µm in wavelength. As infrared energy strikes an individual bolometer element, the
element increases in temperature, and its electrical resistance changes. This resistance change is
measured and then processed into temperature values which can be represented graphically in an
infrared image. [Source #10] The quality of images created from microbolometers has continued
to increase, which makes the accuracy of the device increase drastically. A good candidate for
the microbolometer chosen would be the PICO640 LWIR detector. This sensor has recently been
selected by Ulis, a French infrared vision specialist company, for portable thermal imaging
equipment [Source #8]. This device features a weight of about 10g, a foot print of 24x24 mm2,
and a power consumption of less than 0.160W. These specifications, along with a 10ms response
time, which supports 50Hz thermal imaging applications, make this product a prime candidate.
Similar products should be considered to try to match these specifications.
Another type of sensor that should be used in the system would also be a shortwave
infrared (SWIR) camera. Although SWIR sensing units are not
commonly known to be used in thermal imaging devices for a long
distance, the Goodrich Corp. ISR Systems has made advancements
in the technology. Their sensors now use an innovative Indium
Gallium Arsenide (InGaAs) technology. SWIR sensors are much
more sensitive and have a higher resolution than the LWIR microbolometers [Source #11].
Having to meet the system requirements, a good candidate for the project has just been released
by Goodrich ISR Systems Inc. The SU1024LDM, seen on the left, is a new line-scan camera that
has a 1024-pixel imager and is very compact (76 mm x 74 mm x 61 mm). The unit is very easily
mounted, with 4 of its 6 sides having mounting apparatuses and this unit is very rugged with the
ability to operate in temperatures ranging from -10 to +50 degrees C [Source #12]. Meeting
these specifications would be ideal for the project, if this specific sensor is not chosen.
The project would integrate both the SWIR and LWIR sensing units into the system.
When used in conjunction with each other these two units allow the user to be able to allow
thermal imaging during a troublesome phenomenon called thermal crossover [Source #4].
Thermal crossovers typically occur during the sunrise and sunset, and this can cause thermal
imaging devices to be rendered useless. This occurs when a thermal sight encounters a condition
where some inactive targets without an internal heat source will warm up or cool off to the same
temperature as the background. If this temperature is not big enough to be detected, the thermal
imaging device is useless [Source #9].
Using two types of sensing units could be costly, and make the project more complicated.
However, there are a lot of benefits that are received in doing so. The unit would have the
accuracy of a SWIR sensor and the range of a LWIR sensor. This makes the product prevent
false readouts, and allows the product to have ultimate functionality.
Other Organizations Involved
There are a few organizations that are involved with discovering thermal imaging
products. This seems to be a rather popular field of study that is coming up in the future. Irvine
Sensors Corp, which is a company based out of Costa Mesa, CA, is a leading edge company
engaged in the development and sale of miniaturized infrared and electro-optical cameras, ultra
high speed image processors, 3D laser imaging systems, and stacked chip assemblies. This
company has recently formed a brand new division in their company solely devoted the
development of thermal imaging sensors. This Thermal Imaging Division is sought to develop
innovative sensors that meet the company’s profile of miniaturized products. [Source #7].
Another organization that is seeking a product that is very similar to that of the ‘Last Man
Thermal Imaging System,’ is the U.S. Defense Advanced Research Projects Agency (DARPA).
This company, which consist of military electro-optics scientists, are reaching out to the industry
in search of ways to implement a “low-cost room-temperature infrared (IR) cameras based on
cell phone CMOS camera technology in which the imaging sensor, optics, and electronics are
fabricated at the wafer level.” This program is an effort by the agency to equip each warfighter
with a cellphone that has a thermal imager which has a low-power-consumption yet state of the
art performance. [Source #1 & 2].
Goodrich Corporation’s ISR Systems’ Princeton team, formerly known as Sensors
Unlimited, Inc. has recently developed and implemented the smallest “SWaP” (size, weight, and
power) infrared camera for unmanned vehicles. This SWIR camera, is used in conjunction with a
long-wave infrared (LWIR) microbolometer. This system has been installed on the Raven, an
unmanned aerial system used by the US Military. This camera utilizes advanced Indium
Gallium Arsenide (InGaAs) imaging technology which is known for its’ uses in industrial,
commercial, military, agricultural, and scientific markets. [Source #4].
Along with the companies mentioned above, the Military in general is very interested in
the implementation of thermal imaging into their vehicles. They have been noted for signing a
$15.9 million contract with FLIR to develop infrared sensor pods for their Black Hawk
helicopters [Source #6]. They also have signed a $59.1 million contract with General Dynamics
to develop 21 of the most prominent tanks in military combat. One of the main features on this
tank that stood out to the US Military was the M1A2 System Enhancement Package. This system
includes a digital control, second-generation thermal imaging systems for the commander's
independent viewer and a gun sight that uses 2nd generation forward-looking infrared (FLIR)
sensors [Source #3].
Strengths
A strength to this project is the information regarding which specific sensors can be used,
and how they help to make the sensing unit complete. The report contains specifics with size,
weight, and power consumption of the sensors. This information is very helpful for the design
component. This will help the project to note how much space we need for the sensors to be
mounted.
Weaknesses
A weakness of the report would be the fact that it is not known exactly how to integrate
both sensors to work together. There is insufficient information, on to what type of signal the
sensors will output to the microcontroller. The sensors must work together to make the unit very
efficient. The integration and circuitry is a major part missing from the project, but that only
poses a weakness for now.
A major threat to this project would be the overall cost of the project. Being that the
project calls for portable and light weight sensors; the size and cost are inversely proportional.
That is with decreasing size comes increasing cost. The accuracy of the sensor also causing the
cost to increase. The more accurate the sensor, the more it will cost. That being said, there is a
big threat to this project, being we have a small fixed budget to work with.
Opportunity
This project is also very popular in the military field, which allows for a good amount of
information to be released. There is a strong desire for thermal imaging devices within the
military with allows for a great opportunity for this project.
Threat
A threat to this project would be a replacement product being introduced into the market.
As mentioned before, there already are attempts to make portable thermal imaging devices for
each soldier in the army. If products like this are introduced before our product is finished, it
could deem the entire project useless when all is said and done.
Microcontroller
The microcontroller necessary for this project will have to be powerful enough to handle
the code that will process the input information and provide an output. This processing power
will have to be balanced with size, making it portable enough not to be a burden on the soldier.
All of these qualities will have to be balanced with price, in bulk amounts this component will
have to be affordable.
One possible variety of microcontrollers that can be used is the PIC24 family from the
Microchip Company. These come in a range of packages with various physical sizes, pin counts,
and options for external or internal clocks. These chips can have up to 128 kb of flash memory
allowing for focus on programming and fewer external components; this should help in reducing
the size of the final product. These chips are also designed for rapid communication with
external peripherals such as displays making them ideal for this project.
Microchip also procieds a range of development tools for their products. Programming of
the chips can be accomplished through the use of their integrated development environment
MPLAB, which is a C based compiler. Along with a compiler Microchip also provides
development boards for their chips. These tools come with documentation and are aimed at
helping developers produce their end result.
Working in partnership with microchip Express Logic inc. has created a real time
operating system for the PIC24 family of controllers. ThreadX is a real time operating system
that provides control of interrupts, event management, thread synchronization and a host of other
functions. It is a tool that comes with extensive documentation as well as training so it should be
an accessible method of programming the microcontroller. The format for ThreadX appears to be
C based, since this is a language that most students are familiar with it should make it easier to
use for this project. The ThreadX is not limited to just the PIC24 microcontroller but to multiple
families produced by different companies; these include the C54x from Texas Instrument and the
AVR32 from Atmel. Having a range of microcontrollers compatible with this system will give us
more flexibility in the final design of this project.
The Microchip Company isn’t the only possible source of microcontrollers. Atmel
is a producer of the AVR microcontrollers which are another very popular group of chips. The
ATmega family of controllers is very popular today with hobbyists and garage developers. It is
used in the very popular open source Arduino system. To ensure ease of use there is a multitude
of documentation and development tools for this family of microcontrollers. A simple internet
search will show the popularity of this chip and the large variety of ways in which it has been
integrated into all sorts of projects.
Strength
Strength for this project is the documentation available for the microcontrollers that were
proposed. Data sheets as well as tutorials are available on the company websites as well as
various sites aimed at assisting developers.
Weakness
The primary weakness of this report is the indecision on the final choice of microcontroller. Two
families have been presented but no specific chip has been chosen. The final decision will
require further inquiry into the exact needs of the project and the ability to program the chosen
microcontroller.
Output device:
Summary:
Although, all three types of output devices have benefits the best output device that
should be used for this project is the ear piece. The ear piece should be used because it has the
ability to notify the soldier of a potential threat in the least compromising way. If a LED is used
and a unit is out during the night the light could easily be detected by the enemy also if a
vibrating motor is used there is a chance that the soldier may not feel vibrate. After researching
several types of tactical earpieces the best choice for our project would be selecting the FreeLinc
FreeMotion 200 Wireless headset. This device is a wireless ear piece that can easily be worn by
the soldier. The device creates a secure communication area around the solider which would
block interception and/or interference from the potential enemy. The secure area around the
soldier cannot be hacked either. The ability for no interception and/or interference along with
the inability for the secure area to be hacked is because the device utilizes the Near Field
Magnetic Induction which uses “a non-propagating, quasistic magnetic field technique to achieve
wireless connectivity between two devices”. NFMC does not depend upon using an
electromagnetic field but instead uses a magnetic field localized around the transmitting device.
FreeLinc the creator of the FreeMotion 200 Wireless headset partnered with Aura
Communications Technology, Inc. to produce the LibertyLink. LiberyLink uses the concept of
Near Field Magnetic Induction. LibertyLink’s magnetic communication creates a “bubble” that
surrounds the user and it is private and secure. The “bubble” is only useful for area
approximately 5 feet around the device. The ability to create this “bubble” allows for a lowcosting and lower-operating (requires less power) device.
Constraints:
Like any good design idea there are always constraints one must consider when creating a
new device. The constraints that are related to this device are as follows:
- Environmental: The FreeMotion200 can only operate between the temperatures of -4 F
to 140F. The US military is currently deployed to locations like Iraq and Afghanistan where the
average summer temperature is 123F; although this temperature is below the extreme limit the
functionality of the device still could be compromised at this temperature. Also the military can
be deployed to locations where the average temperature could be colder then -4F therefore the
device’s functional temperature range should be tweaked if it is going to be completely useful to
the United States military.
- Battery Life: The device uses a lithium polymer battery. Although there are numerous
advantages to this type of battery there are still draw backs that could affect the overall device
the group is trying to design. Lithium polymer batteries are sensitive to high temperatures, also
if the device is compromised while the soldier is wearing it, the battery could further harm the
soldier. Another issue regarding the battery is that it only has 20 hours of continuous “talk”.
Although road marches, patrols, and special operations occur quickly if a team is in a remote
location the ability to recharge the battery could be an issue because it requires a wall or car
charger. The device maybe better suited if it could be modified to have interchangeable
batteries.
- Price: The cost of the FreeMotion200 is $249.00 dollars. The device would be bought
in bulk which could lower the overall cost but for just an output device the price is very high,
which would affect the overall price of the product and its ability to sale.
Professional/ethical Responsibilities:
As the creators of the device we would promote this product as adding additional safety
to soldiers that are deployed defending our nation. Safety of the soldier is a very important
factor in this product because if the product fails we are endangering the lives of a service
member which is something we do not want to do. This device will have to routine updates and
test to ensure that it cannot be hacked or detected by the enemy. Also we would have to make
sure the soldier understands that this device is for added safety but they still should not let their
guard down and become reliant on this device. Soldiers must still ensure the safety of their area
of responsibility while they are on a mission.
SWOT
Strengths: The strengths of using a ear piece as the output device for this product is that it
is the most discrete device. An ear piece can easily be hidden under a helmet, and the soldier
will be able to register signal from this output device. If an LED light was used that could easily
be seen especially in poor lighted and dark areas. A soldier could easily miss a vibrating motor
going off as well if that was used as the output device. The choice of using the FreeMotion200
ear piece is that it provides a secure, discrete device which is exactly what the group is looking
for. The secure, un-hackable network provides the discrete a soldier needs while wearing the
product.
Weakness: An enemy could eventually figure out a way to detect the device. The
current size of the ear piece needs to be smaller so that it more comfortable to wear. Also the
ability to recharge the battery in a remote location could create an issue for the soldier.
Also weakness of the overall product is integrating the sensors to work in conjunction
with the microcontroller and the output device and the overall price of the product. As
mentioned earlier the ear piece alone is approximately $250, the more accurate sensors we
choose along with the fastest microcontroller will easily add to our overall costs.
Opportunity: The idea of a wireless, secure ear piece is very popular right now therefore
utilizing the market a less expensive ear piece could be found. The overall opportunity for this
project is very high right now due to the military need to thermal imaging devices and finding
ways to further protect soldiers from the enemy.
Threats: A threat to this device is the cost of it but as competition for creating devices
similar to this one grows the price should be driven down. A threat to the overall project would
be another group producing a product similar to ours. The US military wants to protect every
soldier and if a similar product is introduced before ours, our efforts would be useless.
Resources
Infrared Temperature Measurement Theory and Application
http://www.omega.com/techref/iredtempmeasur.html
How Thermal Imaging Works
http://www.morovision.com/how_thermal_imaging_works.htm
Cooled vs Uncooled Devices
http://www.flir.com/uploadedFiles/ENG_01_cooledVSuncooled.pdf
Performance of a Cooled Photo Diode Array
http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=00094566
Low Cost Thermal Imaging For Power Systems
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=702751
LED Lights
http://www.theledlight.com/
Vibrating Motor
http://www.melexis.com/Sensor-ICs-Hall-effect/Hall-effect-Fan-MotorDrivers/Vibration-Motor-Driver-639.asp
http://www.allegromicro.com/en/Products/Design/an/AN205049.pdf
http://cdn.makezine.com/make/arduino/GettingStartedWithArduino_ch04.pdf
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4381134
http://www.arduino.cc/
Basic concepts of real-time operating systems by David Kalinsky (nov. 18 2003)
http://cdn.makezine.com/make/arduino/GettingStartedWithArduino_ch04.pdf
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4381134
http://www.arduino.cc/
All Sources – Thermal Imagingin
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Output Device
http://www.defensereview.com/freelinc-freemotion-200-wireless-headset-secure-tacticalcommunications-bubble/
http://www.freelinc.com/products/freemotion.php
http://www.army-technology.com/contractors/navigation/cj-components/
http://www.wireless-center.net/Wireless-Internet-Technologies-and-Applications/1270.html
http://www.britannica.com/EBchecked/topic/56126/battery/45850/Lithium-batteries
http://batteryuniversity.com/learn/article/is_lithium_ion_the_ideal_battery
http://www.britannica.com/EBchecked/topic/293631/Iraq/22930/Climate