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Temperature Controlled Jacket




   ECE 445 – Senior Design

       Design Review

Temperature Controlled

   Namit Gupta
   Akash Maitra
T A : A r i e l Moctezuma
         Group #4

   I. Introduction

    The project encompasses a jacket that can regulate its temperature from within to suit
the needs of the wearer. A lot of times, people wear several layers of clothing before
putting on a jacket (i.e during winter) only to realize that they are either too hot or too
cold. With this jacket, the user can set the jacket's temperature between a particular range
which he / she may find comfortable. A LCD will be attached to the inner lining of the
jacket; the user will be able to adjust the temperature using the LCD display, which
displays the current temperature. Furthermore, the coat will use a single line bus control
to offset the weight and make the jacket more wearable.

    For heating the coat, we will be using a heating pad mechanism. For cooling the coat,
we will be using a laptop cooling mechanism. The temperature sensors will be used to
monitor the temperature of the coat's inside and depending on if it is too hot or too cold,
the heating or cooling system will go off.

    In addition, the jacket will be monitoring the heating/cooling systems to make sure
that they are operating in acceptable temperature ranges. The electronic interface among
all the sensors with the microcontroller (PIC 18F4550) will be done using a serial line
bus interface. As a result of this, the complete data movement in the circuit would take
place using a single wire. The information at / from each sensor is decoded accordingly.
The major advantage of this system is the fact that the weight of wires is exponentially
reduced and the end product would be more pleasing aesthetically.
Some of the system features and end user benefits are as follows:

1.1)   Benefits

          In cold weather, the use of layering the upper body is minimized.

          Automatic temperature control of the jacket makes sure that the user does not
           have to worry about switching on/off the system.

          Gives the user the peace of mind that in whatever outside temperature they
           may be situated in, he/she will feel snug within the confines of our jacket

1.2)   Features

          Single line bus control makes the jacket easy to wear and light weight.

          The LCD displays the current temperature of the jacket and allows the user
           the ability to choose what temperature he/she would like the coat to feel like

          The cooling system works as to ventilate and maintain a specific temperature.

      Infrared sensors will detect if someone is wearing the jacket or not and take
       appropriate action. i.e. turning the jacket off / on.

      If hardware or software fails, the heating / cooling will switch off
       automatically thereby protecting the wearer from injury

      A USB battery charge equipped with the jacket will allow the user to charge
       the jacket while they are using their computer

      We will try to have our jacket reach the desired temperature set by the user
       within 10 minutes of turning on.

II. Design
       2.1) Block Diagram

                           A single serial line is utilized
                           to communicate with all the
                           devices. The Master PIC will
                           communicate with the Slave
                           PICs enable data to be sent
                           using a single line. The
                           information acquire from the
                           sensors will be sent to the
                           Slave PICs, which will then
                           send the data to the Master
                           PIC to be analyzed.

       2.2) Block Descriptions
PIC Microcontroller
       The PIC microcontroller will be used to communicate with the sensors, LCD
Screen, heating/cooling systems and the temperature sensors. It is the brain to our
heating/cooling jacket and will send data appropriately based on the input from the

Infrared Sensor

       An inferred sensor will be placed at the collar of the coat. It will detect heat
radiating from the user. Since we do not plan on placing nearby heating/cooling
systems by the collar, nothing should interfere with the sensor’s results.

Temperature Sensors

       The temperature sensors will monitor the heating and cooling systems to
make sure that the systems operate within a predetermined temperature range. If
they exceed the range, the system will shut off. This information will be relayed by
the sensors. In addition, these sensors will be used to control the individual heating
areas of the coat so that if one area of the coat is already hotter than the user set
temperature, the heat system will remain off in that particular location however the
other locations, assuming they are below the user set temperature, will continue to
be on. The temperature sensors will communicate with the PIC using a single serial
Serial Display Module

        There will be an LCD display that will be programmed to show which system
is currently on as well as which of those regions in the coat are currently being
heated or cooled. It will show system errors as well.
Cooling System

       The cooling system will have several fans and ventilation ports similar to the
way they use in CPU's to circulate hot air out of the coat into the atmosphere. These
fans and ports will be placed strategically on the coat so that the hot air is released
from the coat.

Heating System

       There will be multiple heating systems in the jacket. These heating systems
will have sensors that monitor the temperature at those exact points and then will
send the temperature data to the LCD to be displayed. The heating systems will be

designed using heating coils, which will be wrapped around in a protective covering
to protect the wearer. We will be using Polyimide Film Insulated Flexible Heaters.

2.3) Performance Requirement

      The performance of our jacket will depend on a multitude of factors including the
       accuracy of the temperature sensors as well as the efficiency of our
       heating/cooling systems. We need our circuit to be able to turn on/off on its own
      We should be able to set the jacket temperature as per the user requests with a 4%
       tolerance level.
      We expect the jacket to have a good response time of less than one minute.
      The jacket is supposed to be water-proof because electric circuits could short
       circuit if this not taken care off.
      The safety features have preference to user requirements and if the user intends
       for the jacket to perform in a particular way but the safety norms are violated, the
       user’s request is discarded.
      The battery must be able to last about half an hour.

   III. Verification
        3.1) Testing Procedures

1) Temperature sensors: The data from the temperature sensors will be transferred to the
slave PIC. The slave PIC will communicate to the main PIC and tell it what the current
temperature is at a particular region. The same data will also be sent to a plotting
software such as Eagle in the computer to determine the variation in temperature at a
given instant and how the sensors behave for various inputs of temperature by the user.

2) Force Sensitive Resistor: The force sensitive resistor is a variable resistor which
changes its value depending upon the mechanical force applied to it. We will send the
value of the current resistance of the FSR to the computer and make sure that its value
changes for various amounts of pressure applied to it.

3) PIC microcontroller: PIC will be programmed in C programming language and we
will take a modular approach to make sure that we are on right track. First, we will test
one temperature sensor if it works fine or not. Then we will add one more sensor to make
sure that the PIC performs as expected to. Finally, all the sensors and heating pads would
be integrated to make it a lumped system.

4) Touch screen Liquid crystal display: We will have the touch screen display current
temperatures and areas of the jacket which are on/off. The testing of the LCD is pretty
simple and would be done with manual inspection.

     3.2)Tolerance Analysis

       The analog temperature sensor measures voltage from the range of 400 uA to 5
mA. This voltage range allows us to measure temperature in absolute terms of kelvin.
The range of operation is -55 C to 150 C. The sensor is accurate to one degree Celsius.

        This FSR will vary its resistance depending on how much pressure is being
applied to the sensing area. The harder the force, the lower the resistance. When no
pressure is being applied to the FSR its resistance will be larger than 1MΩ. This FSR can
sense applied force anywhere in the range of 100g-10kg. These sensors are simple to set
up and great for sensing pressure, but they aren't incredibly accurate. We will use them to
sense if it's being squeezed, but we may not want to use it as a scale. This is perfectly fine
for our application.

    For the PIC microcontroller, we cannot compromise with their tolerance as they have
to be working all the time at 100% efficiency. Their operation range is from -40 C to 85
C. This is an acceptable temperature range because we do not expect the temperature
inside the jacket to exceed 40 C at any stage of time. Although, considering the effects of
internal heating of PIC, we will make sure that the microcontrollers are placed at a fair
distance from the heating pads.

    The coat will have a tolerance feature as a way to conserve power. Ex. If the user sets
the coat to 72 degrees and all the areas reach 72, the system will not turn on if suddenly
the coat is 71 degrees. We will make sure the coat turns on when the coat becomes either
69 degrees or 75 degrees. This is essentially how our home cooling systems work. The
test runs by maintaining a logic in the microcontroller and making sure that all sensors
more or less operate at the same temperature by switching off any of the irrelevant
sections. Basically, we allow 4% of leverage on the temperature that the user enters the
jacket to reach. 4% tolerance is not a bad trade-off so as to save battery power.

   IV. Cost and Schedule

       4.1) Cost Analysis

          a) Labor

                 Namit Gupta       ($50/hr) x 2.5 x 150 hours = $18,750

                 Akash Maitra      ($50/hr) x 2.5 x 150 hours = $18,750

                 Labor Cost                                         $37,500

             b) Parts List

Parts List           Price           Quantity         Total Cost Estimate

Temperature          $1.35 each      10               $13.50

LCD            $60                   1                $60

Infrared Sensor      $2.73           2                $5.46

PIC 18               $2.50           2                $5

Power Button         $1.95           1                $1.95

Jacket               $35             1                $35

Heating Coils        $15             6                $90

Cooling Fans         $15             2                $35

Rechargeable         $18             2                $36

Wiring               $10             1                $10

Total Cost                                            $286.91

             c) Grand Total

                       Total Cost (Labor + Parts) = $37,500 + $286.91= $37,876.91

  4.2) Schedule

Week 1 (02/07/11)   Proposal                       Akash and Namit

Week 2 (02/14/11)   Design Review                  Akash and Namit

Week 3 (02/21/11)   Dismantling the heating pad    Namit
                    Sewing the heating wires to    Akash
                    the jacket

Week 4 (02/28/11)   Placement of infrared          Namit
                    Placement of temperature
                    sensors                        Akash

Week 5 (03/07/11)   Interfacing the IR sensor to   Namit
                    the small PIC
                    Interfacing the temperature
                    sensor to the small PIC        Akash

Week 6 (03/14/11)   Interfacing the LCD display    Namit
                    to the central PIC
                    Interfacing the control
                    buttons with the LCD           Akash

Week 7 (03/28/11)   Programming the central        Namit
                    PIC for IR sensor
                    Programming the central
                    PIC for temperature sensor

Week 8 (04/04/11)   Interface the cooling pads     Akash and Namit
                    with PIC

Week 9 (04/11/11)   Testing the effectiveness of   Namit
                    separate modules of heating
                    Testing the cooling pads       Akash
                    and IR sensors

Week 10 (04/18/11)   Test for the unit’s        Namit
                     functionality as a whole
                     Debug the system

                     Prepare for Demos
                                                Namit and Akash

Week 11 (04/25/11)   Demo                       Akash and Namit
                     Prepare Presentation       Akash and Namit
                     Begin Final Report         Akash and Namit

Week 12 (05/02/11)   Complete final Report      Akash and Namit

Week 13 (05/09/11)   Final Exams                --

                             Safety Flowchart

The above diagram shows how errors would be read on the LCD for various
malfunctions that could take place in the system.

                          Heating/Cooling System

Flowchart of how the heating and cooling systems switch on/off for various
predefined conditions.


The diagram shows how the master PIC is connected to the slave PICs, which are in
turn connected to various types of sensors.

                                     Serial Display Module

    72○ F  22.2○ C                                                        Next


    Set Temperature:                                                            Off

  Error # 1: Heating Pad Over                            BATTERY
  Specified Temperature Range->                          POWER
  Shutting System Off

This is the first screen that will be used to allow the user to set the temperature of
the coat. It will also display if the heating/cooling system is on or off and if any
errors have occurred in the system.

This is the second screen that will be used to show what areas of the jacket
currently have a heating/cooling system on.

                           Power Consumption and Simulations
We will use two types of power sources in our system. The first source of power is a
complicated issue because this is needed to power the heating pads. The best option
available to us for this operation is a Lithium poly battery (25C, by tenergy). This battery
provides 11.1 volt at 2200mAh. This approximately equals to 24.42 watt hours. Let us
calculate the amount of time the heating pads would be able to run before the battery runs
We intend on using KHLV rectangular heaters which could be obtained from the The heater that we have finalized is the KHLV 105(*). It is a
rectangular heating strip with dimensions of 1 inch by 5 inch. The total power required by
this strip is 50 watts. According to the manufacturer, the optimal applied voltage would
be 28 volts. But in our situation, we only have 11.1 volts at 5.1 Ahrs. This is fine because
these heating strips are highly efficient and they can reach to a peak temperature of 200
degree Celsius.
If we calculate the resistance of these heating strips,
R= V2/P=(28)2/50= 15.68 ohms
Power generated for each heater would be equal to, P= (11.1)2/ 15.68 = 7.85 watts.
Since, the applied voltage is 11.1 volts, the current flowing through six heaters is:
I= 11.1*6/(15.68) = 4.24 A
The current flowing through the control unit is in the range of milli amperes and micro
amperes. Considering the fact that heaters are consuming a lot of current, the control unit
will not take more than 0.5 amperes. Finally, we have a total power consumption of 4.75
Total number of hours we can run the battery without considering the effect of self-
discharge= 5.1 Ahrs / 4.75 A = one hour and five minutes.
A lithium polymide battery has a self-discharge rate of 3% per month. So, if the user
keeps his jacket unused for one year, we only lose 36% of the voltage rating of 11.1 volt.
Concluding this part, we have decided that one Li poly battery would be able to power
six strips of heating pads (5 sq inch each) for about one hour.
The second part would power the PICs, cooling pad (generic cooling pad with three fans
and takes 2.5 watt hours) and the touch screen LCD screen (by 4D system, ulcd-28pt,
requires 3.5 volt of input power). This would be achieved with a voltage regulator that
converts 11 volt into 5 volts. Since, the power consumption for these devices is very
small, we need not worry about their longevity. If, for some reason, we need more power,
we may simply add another battery in series to the original battery and it will solve our

                                      Master PIC

We will be using PIC 18F4550 as our Master PIC. The specific pins used for data transfer
are Serial clock (SCL) – RB1/AN10/INT1/SCK/SCL and Serial data (SDA) –

                                       Slave PIC

We will be using PIC 18F4550 as our Master PIC. The specific pins used for data transfer
are Serial Clock (SCL) – RC3/SCK/SCL and Serial Data (SDA) – RC4/SDI/SDA.

                                Serial Display Module

This is the circuit diagram used to communicate with the serial display module and
the Slave PIC.

The circuit above uses 3.3k resistors attached to both the SDA and the SCL because
they need pull up resistors as either the master or the slave can hold the line low to
stop communication.

         From the onset of this project, we would like to make it clear that heating jackets
do prevail in the market, which rely on heating pads to accomplish the goal. We
differentiate ourselves from other companies by using single line serial bus as an
interfacing mechanism. What this means from a broader perspective is that their would
only be a single wire from the central control unit that transmits data to all the other parts
of the jacket where the sensors are located. Traditional heating jackets used parallel
interfacing whereby the number of wires used to interface was linearly proportional to the
number of sensors in the jacket. On top of this, we also use automatic temperature
controlling mechanism, which other companies have not used. We intend to make this
jacket environmentally sustainable by using Li-poly batteries, which do not leave any
residue when discarded. Many people are expected to benefit from this jacket because it
is light weight and leaves most of the processing to be done by the computer instead of its
user in maintaining optimal temperature.


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