Gas Bot - Toxic Gas Sniffing Robot
ECE4007 Senior Design Final Project Report
Section L03, Gas Bots Team
Project Advisor, Dr. Erick Maxwell
Amrinder Chawla, Team Leader
Robert Brown
Enkuang Wang
Gowtham Tamilselvan
Saurabh Pandey
Anurag Kadasne
Submitted
December 14th, 2010
Table of Contents
Executive Summary ......................................................................................................... iii
1. Introduction.................................................................................................................. 1
1.1
1.2
Objective ............................................................................................................. 1
Motivation ........................................................................................................... 1
2. Project Description and Goals .................................................................................... 3
3. Technical Specification ................................................................................................ 6
4. Design Approach and Details
4.1
4.2
4.3
Design Details ..................................................................................................... 10
Codes and Standards ........................................................................................... 16
Constraints, Alternatives, and Tradeoffs ............................................................ 18
5. Schedule, Tasks, and Milestones .............................................................................. 19
6. Results and Acceptance Testing ............................................................................... 20
7. Budget and Cost Analysis ......................................................................................... 23
8. Conclusions and Future Work ................................................................................. 25
9. References ................................................................................................................... 26
Appendix A ....................................................................................................................... 28
Appendix B ....................................................................................................................... 29
Appendix C ....................................................................................................................... 30
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Executive Summary
The Gas Bot allows emergency response teams to detect the toxicity levels of carbon monoxide
(CO) wirelessly and provides assistance to those trapped in the toxic area. With the attached camera,
the remote user receives live video feed that allows the user to navigate the affected area. The onboard
gas sensor sends gas concentration values to the remote computer, allowing the user to identify areas
of high toxicity. The safety kit encompasses a gas mask and a filter to help people who are trapped
inside the leak. The eBox (model number: 3300/3310) acts as the hub of the Gas Bot where all the
information is accumulated and processed on a Windows CE 6.0 platform. The sensor and the camera
are connected using a serial port cable and a universal serial bus (USB) cable respectively to the eBox.
Using the Wi-Fi card present in the eBox, information is sent to the controller. The gas sensor is
interfaced to the eBox via a programmable controller (mbed). A graphical user interface (GUI) based
software has been programmed using C#. This software enables the user to wirelessly control the Gas
Bot and read CO concentration levels. The Gas Bot weighs approximately 4.2 kilograms and measure
13.4" diameter x 6" height. This makes the Gas Bot a small sized and portable device. The cost to build
a Gas Bot is $142.98. This device reduces the rescuer’s exposure to CO and can provide timely
assistance to those in need. The benefit for the Gas Bot is that it eliminates the possibility of a human
having direct contact with the toxic gas.
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Gas Bots
1.
Introduction
The Gas Bot team spent $142.98 developing a prototype device that can detect the
concentration of toxic gases and provide primary assistance in case of a chemical leak. This device can
enter gas leak affected areas, provide live video footage, and send gas concentration levels wirelessly
to a remote personal computer.
1.1
Objective
The objective of the Gas Bot is to detect concentration of toxic gases like carbon monoxide in
places affected by gas leaks. The Gas Bot is equipped with a camera and a gas sensor. The Gas Bot can
be controlled wirelessly by a remote user. The camera sends live video stream to the controller for
navigation purposes. The gas sensor is able to send gas concentration data to the remote user.
Additionally, a safety box has been installed on the Gas Bot that can contain emergency assistance
materials like gas masks and walkie-talkies for individuals trapped in the affected area. The Gas Bot
will primarily be used by fire departments, chemical factories, warehouses, and environmental health
and safety organizations.
1.2
Motivation
Carbon monoxide (CO) is a highly hazardous and toxic gas. Short term exposure to CO can
lead to hypoxic injury and neurological damage. Long term exposure to high concentration of CO can
even lead to death. Approximately, more than 15,000 people seek medical attention for carbon
monoxide poisoning every year [1]. On average, 500 people in US die every year from carbon
monoxide poisoning [1]. Hence, there is a strong need for a device that assists in detection of such
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gas that will minimize the harmful impact on human health.
There are several technologies that emergency personnel use to deal with gas leaks, like
cameras and gas sensors. However, there are limitations to the capabilities of these technologies when
used independently. For example: security cameras give a limited and static view of the gas affected
area. If a warehouse or factory lacks cameras, then it would be cumbersome for the fire department to
see if someone is stuck or passed out inside the area. Furthermore, gas sensors require an individual to
be present in the affected area to operate the sensor and read the concentration levels. If the individual
is exposed to high concentration of carbon monoxide, it can lead to harmful effects on his/her health.
The Gas Bot integrates these two technologies on an iRobot Create platform. This device
allows the emergency team to combine the merits of a video feedback and continuous gas
concentration level measurements on an easily navigable device. It integrates a safety box that
provides basic emergency equipment for people trapped in the gas-affected area. Currently, no device
in the market exists that combines these three different technologies. Such a device will aid the
emergency personnel to get a wider view of the affected area along with live feedback of concentration
levels that will prevent human exposure. Figure 1 shows a schematic of the Gas Bot and its
components.
Figure 1. Schematic of the Gas Bot and its components.
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2.
Project Description and Goals
Overview
The fundamental goal of the Gas Bot is to assist emergency crisis teams in case of chemical leaks.
The Gas Bot has the capability of sending critical information including live video footage and carbon
monoxide concentration levels to the response team. A single operator can remotely maneuver this robot
around the building using a personal computer. Table 1 lists the cost and design objectives that were
proposed in the proposal. All the proposed objectives were successfully met in our final prototype.
Table 1. Status of Objectives Defined in Proposal
Objectives
Live video streaming
Detect concentration of CO
Safety box for emergency assistance materials
Status
Met
Met
Met
Easy to Graphical User Interface(GUI)
Met
Portable and Easily Navigable Device
Met
Total cost under allocated budget of $440
Live wireless feedback of gas concentration
Met
Met
The prominent features of the Gas Bot are discussed in detail below.
Live Video Streaming
A webcam console window was designed to operate on the Windows CE 6.0 platform. The console
was designed using the ECE 4180 textbook [11] as a reference. This was in accordance with our proposed
use of the Logitech webcam in the proposal. The console window enables the video streaming on the
eBox. The remote user is able to receive the video stream by using the eBox’s export view feature. Figure
2 shows the screenshot of the video stream.
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
The camera is mounted on a plexiglass stand providing a front view.

Image refresh rate can be varied from 5 frames per second (fps) to 30 fps.

Image size can be varied from 128 pixels x 160 pixels to 640 pixels x 480 pixels.
Figure 2. Logitech Pro 9000 series camera providing live video.
Measurement and Feedback of CO Concentration
A console window was designed to transfer data over a serial port interface on the Windows CE
6.0 platform. The console window reads and prints CO concentration levels (in ppm) from the sensor. To
interface the CO sensor with the eBox, we used a mbed micro-controller as opposed to a phidget kit that
we had originally proposed. We decided to switch to the mbed board because it was easier to program.
The remote user is able to read the concentration values using the export view feature. The export view
feature uses Wi-Fi to transfer the eBox view to the remote computer. Figure 3 shows the screenshot of the
console displaying concentration values.
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
Concentration values are read every millisecond

Transfer rate between Gas Bot and remote computer depends on quality of Wi-Fi connection
Figure 3. Console window with ppm values.
Graphical User Interface (GUI)
The Gas Bot is controlled using a GUI programmed in C# as shown in Figure 4. The GUI is based
on the work of Dr. Hamblen and previous ECE 4180 projects [15].

Has both mouse and keyboard compatibility.

Can be used to control the speed of the Gas Bot

Can be used to move the Gas Bot forward, backward, left, and right
Figure 4. CreateRemote GUI.
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Safety Kit
The safety kit was designed to maximize and efficiency space on the iRobot. The kit was designed
by a Georgia Tech Industrial Design student – James Slack. The safety kit is made of sign foam that is a
type of high density urethane. The back is covered with an acrylic cover to provide support. The kit latches
onto the back of the iRobot as shown in Figure 5, making it robust.

Can accommodate a full size gas mask and filter

Has an open top design allowing more space to store a communication device.
Figure 5. Safety kit containing gas mask with filter.
3.
Technical Specifications
Main Control Device
Figure 6 shows the setup of the Gas Bot. The Gas Bot setup and installation process involved
procuring an eBox, a Logitech webcam, iRobot Create, mbed microcontroller, and a carbon monoxide gas
sensor. The gas sensor was mounted on a bread board and connected to the mbed microcontroller which
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communicated to the eBox via serial cable, and the web cam was connected to the eBox via USB interface.
The eBox was the main processing unit of the Gas Bot. It communicated to the iRobot via serial cable.
Figure 6. Basic graphical setup of the Gas Bot.
The eBox 3300 is a compact PC which is designed for applications involving limited space, low
cost, and temperature concerns. The technical specifications of the eBox are given in Table 2. The power
supply for the eBox comes from the battery of the iRobot Create. The iRobot Create battery provides a 16
V input voltage. Since the eBox requires a input voltage of 5 V, a voltage regulator is needed to step down
the input voltage coming from the battery of the iRobot to 5 V.
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Table 2. Specifications of the eBox[2]
Processor
MSTI PDX-600-1 GHz (Fanless)
Memory
VGA
256 MB DDR2
XGI Z9S with 32MB DDR2
External 15-pin D-type female VGA connector
Ethernet Interface
Integrated 10/100 Mbps LAN
USB
Enhanced IDE interface, 44pin box header x 1
Type I/II Compact Flash Slot x 1
MicroSD slot (bootable) x 1
Mini PCI Socket x 1 (optional)
RS-232 Port x 2 (optional)
RJ-45 Ethernet Connector
External 6-pin Mini DIN for PS2 Keyboard and Mouse
3 ports (USB 2.0)
Power Requirement
Single Voltage +5V @2A
Dimensions
115 x 115 x 35 mm
Weight
505g
Operating Temperature
+5 ~ +50°C operating temperature
Wireless
802.11 b/g Wireless Networking option
Operating System
Window CE 6.0
I/O
Webcam, Gas Sensor, mbed microcontroller, and iRobot
The gas sensor and the webcam are connected to the eBox. The CO data is sent to the eBox first
and then gets transmitted to the remote user through GT wireless. Logitech Pro 9000 webcam was used as
the primary camera. The specifications of the Logitech Pro 9000 webcam are given in Table 3. The gas
sensor used was the Parallax Carbon Monoxide sensor and its specifications are shown in Table 4.
Table 3. Specifications of Logitech Pro 9000 Webcam [3]
Video Definition
Native 2-MP HD Sensor (Up to 1600 X 1200 pixels)
Interface
Lens
Hi-Speed USB 2.0 Certified
Carl Zeiss® Optics with Autofocus
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Table 4. Specifications of the Parallax CO Gas Sensor Module [4]
Measurement Range
20 ppm – 2000 ppm CO
Interface
Operating Temperature Range
1 TTL compatible input (HSW), 1 TTL compatible
output (ALR)
1.50” H x 1.00” W x 1.00” D
(38.1mm H x 25.4mm W x 25.4mm D)
32°F to 158°F (0°C to 70°C)
Power Requirement
5 V DC @ 165 mA
Dimensions
The mbed board acted as the interface between the CO sensor and the eBox. It converted the
analog voltage output from the sensor into a ppm value and then sent it to the eBox. The technical
specifications for the mbed board are shown in Table 5. The eBox, webcam, and the gas sensor were
installed on the iRobot Create. The iRobot Create served as the mobile platform for the Gas Bot. The
specifications of the iRobot Create are given in Table 6. All necessary components, including the remote
control, battery, 110 V battery charger of the iRobot were included in the standard package.
Table 5. Specifications of the mbed microcontroller
Power Supply
USB/4.5-9V
Model Number
VOUT
Memory
RAM
ARM LPC1768
+3.3v
512kb Flash
64kb
Table 6. Specifications of the iRobot Create [5]
Power Supply
5 V DC/100 mA (max)
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4400
Diameter
Height
13.4”
Weight
6.4 lb
Battery
14.4 V Ni-MH battery
3.5”
9
Safety Kit
The safety kit was a compartment on the iRobot specifically designed to hold items that could help
a person in need. The safety kit was designed by a Georgia Tech Industrial Design student – James Slack.
Main frame of safety kit was made of sign foam and the back had an acrylic cover. The dimension for the
safety kit is 7.6 inches x 4.5 inches for the base, 5.5 inches for the height, and 2 inches for the thickness.
The kit held a full size gas mask with filter during the demo. Other possible rescue items to be kept in the
kit were walkie-talkies and a blanket, but for demo purposes these items were not bought.
4.
Design Details
4.1
Design Details
The main priority of the Gas Bot was to safely and reliably collect and transfer gas concentration
levels. The Gas Bot was designed to prevent human exposure to toxic gases in harsh environments. The
robotic components used for this setup included: webcam, carbon monoxide sensor, mbed
microcontroller, eBox, and iRobot Create. The CO sensor is integrated with the mbed board, which
converted the analog signals from the sensor into digital outputs that were sent to the eBox via the serial
breakout board. The webcam connected directly to the USB port of the eBox. The iRobot Create was preprogrammed to take instructions from the eBox. The eBox is a mini-computer that collected all the data
from the different components and transmitted them via Wi-Fi to the user’s computer. Figure 7 represents
a basic block diagram of the Gas Bot, its components and how they were interfaced.
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Figure 7. Basic design setup of Gas Bot.
CO Gas Sensor Setup
The basic setup for the CO gas sensor and the microcontroller is shown in Figure 8. The analog
input from the CO sensor to the microcontroller is pin TP1 from the sensor itself because it is the pin that
reads the voltage across potentiometer R3. This voltage is useful for generating the CO ppm values.
Figure 8. CO sensor and mbed microcontroller
connection.
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Generating PPM Values from Voltage of R3
All commercial carbon monoxide detectors use ppm values to correspond to the amount of CO gas
present at the location. According to the CO gas sensor datasheet [22], there is a correlation between ppm
values and the internal resistance of the CO sensor. Figure 9 shows the two equations that are relevant to
ppm value calculation.
The first equation is a voltage divider between the internal resistance of the CO gas sensor and the
R3 potentiometer. This equation bascally shows the relationship between the internal resistance of the
sensor and the potentiometer R3. The second equation is the fomula used to calculate ppm values.The
second equation given in Figure 9 is generated from Figure 10. All the data points for Figure 10 are
PPM
extracted from the CO sensor datasheet [22].
4500
4000
3500
3000
2500
2000
1500
1000
500
0
y = 95.501x-1.543
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
(VC-VRL)/VRL
Figure 10. Plot of ppm value vs. ratio of internal resistance and resistor R3.
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Serial Connection for mbed Microcontroller
A serial connection between the mbed microcontroller and the eBox is needed in order to transmit
the ppm values from the microcontroller to the eBox. Since the mbed microcontroller does not have a
direct connection port for serial port, a serial breakout board for the mbed microcontroller is required. The
basic connection is show in Figure 11. The baud rate used for this serial connection is 9600.
Figure 11. Connection between mbed microcontroller and serial
breakout board
Power Supply for the eBox
The eBox powers up using a 5 V, 3 A DC supply. It was powered by stepping down a 16 V DC
output from the iRobot’s battery pack. The 16 V supply was stepped down to 5 V by using a Texas
Instruments 78HT305 voltage regulator. Figure 12 shows a schematic of the voltage regulator and Figure
13 shows a picture of how the voltage regulator was set up in our project.
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Figure 12. Schematic of the voltage regulator circuit.
Figure 13. Set-up of the voltage regulator.
eBox Software and GUIs
Windows CE 6.0 was the operating system (OS) for the eBox 3310. The OS was built using Visual
Studio 2005. Instructions for building the OS can be found in [11]. The drivers for the hardware connected
to the eBox, are also present on the ECE 4180 class website.
A GUI for controlling the iRobot, a window for viewing the camera and a console window for
displaying the ppm values were built using instructions from [11]. The GUI and the windows have been
show in Figure 14.
Figure 14. From left to right- remote control GUI, camera display window and console window with ppm
values
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Safety Kit
A safety kit, made of sign foam was constructed for the eBox. Its base dimensions were such that it
exactly fitted the cargo bay in the eBox. Its base measured 7.6 inches x 4.5 inches, whereas the height
measured 5.5 inches. The thickness of the sign foam used was 2 inches. Figure 15 shows the safety kit
with a gas mask and filter fitted placed inside.
Figure 15. The safety kit
Summary of Components Used
Table 7 lists the features, brand, product details and benefits of the components necessary for
system operation. Each component interfaced with many other parts, so the type of connectivity between
the parts was a key feature to consider. The products were inexpensive, reliable, and user-friendly. Not all
parts listed in the table were incorporated in the Gas Bot. For example, the LCD monitor was used only as
a visual display when programming the eBox during experimental stages.
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Components
Table 7. Components List for the Gas Bot
Necessary Functions
Product Selected
Product Benefit
Web Cam
Real time transmission
of video
iRobot
Mobility and programmability iRobot Create
Serial connectivity to eBox
CO Sensor
Toxic gas, low power, and
cheap
Parallax CO sensor
Integrates with mbed board
eBox 3300/3310
Various kinds of ports and
ease in programming
Laptop
User familiarity
Mini-Computer Multiple inputs slots,
programmable, and wireless
connectivity
User Computer Wireless and C#
programming capabilities
Logitech Webcam Pro USB connectivity
9000
Microcontroller Interface Sensor data to eBox. mbed Board
Analog to digital output
conversion
LCD monitor
Testing purposes; for eBox
HP monitor
programming
4.2
Regulated 3.3v Vout,
multiple pins, connects to
LCD with ease, and serial
output.
Serial connection with eBox
Codes and Standards
Toxic Gas Sensor
The main objective of the Gas Bot was to measure the concentration level of CO. Government and
international regulation agencies such as Environmental Protection Agency (EPA) and International Code
Council (ICC) regularly monitor air quality levels and provide standard values (CO levels). Guidelines
from EPA [6] and ICC [7] regarding acceptable CO levels in the air are tabulated in Table 8 along with the
corresponding health advisory issued by the EPA.
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Table 8. CO Levels in Air in Particles Per Million (ppm) and the Corresponding Health Advisory
Issued by the EPA
CO level
EPA Action
9 ppm (averaged over 8 hours) Acceptable Level
15 ppm
Public Alert
30 ppm
Public Warning
40 ppm
State of Emergency
50 ppm
Significant Harmful Level (serious and widespread health effects
to the people)
Based on the information from the table, it was determined that a CO level of 30 ppm or higher is
not suitable for a normal living environment.
Data Transfer Protocol
The Gas Bot was controlled by a remote user and the gas sensor provided continuous gas
concentration levels to the user (every 1 ms). The selection of the right network for use as the
information carrier was a critical parameter. The Gas Bot was be networked through the GT wireless
network, which was readily available around the campus. GT wireless supports 802.11b, 802.11g, and
802.11a wireless protocols. The eBox was networked with an 802.11b/g network card which was
based on the 802.11 wireless data transfer protocol [8].
Component Integration
The CO sensor (Parallax CO Gas Sensor Module) was designed to be interfaced with a
microcontroller which in turn transmitted an analog signal to an eBox via a serial cable. The serial cable
had to be interfaced with a breakout board to successfully transmit the analog signal. The code for the
microcontroller (mbed) was written in C.
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4.3
Constraints, Alternatives and Tradeoffs
Toxic Gas Sensor
Due to the constraints already in place by various government and regulatory agencies, most of the
toxic gas detectors in the market are EPA standard compliant. The primary deciding factors were the cost,
sensor refresh rate and level of complexity. Keeping these factors in consideration, a low cost analog CO
sensor made by Parallax was chosen for this project.
Wireless Data Transfer
Since the Gas Bot is a user controlled vehicle, it is important to ensure that the information
exchange occurs smoothly, reliably and fast. For these reasons, the decision of choosing a wireless data
transfer protocol was challenging. Table 9 compares the different technologies that were available for
implementation. The technologies under consideration were ZigBee [9], 802.11 (Wi-Fi) and Bluetooth
[10]. The difference among these three technologies is highlighted in Table 9.
Table 9. Comparison of Different Wireless Data Transfer Technologies [11]
Feature
Application Area
802.11b (Wi-Fi)
Web, Email, Video
802.15.1 (Bluetooth)
Cable Replacement
802.15.4 (ZigBee)
Control & Monitoring
Battery Life
Peak Data Rate
0.5 – 5 Days
1 - 7 Days
1, 2, 5.5, 11, (54-802.11g) 1Mbps
Mbps
100 - 1000 Days
250 Kbps @ 2.4 GHz
40 Kbps @ 915 MHz
20 Kbps @ 868 MHz
Power Consumption
1.5 W active @ 20 dBm
45 mW sleep
80 mW active @ 0 dBm
100 mW sleep
60 mW active @ 0 dBm
5–2000 mW sleep
(mode dependent)
Range Indoor
~40 m @ 11 Mbps
~100 m @ 1 Mbps
~10 m
~30 m, Class 1
~10 m @ 0 dBm
Based on the application it was determined that data rate and range were the most important factors
in the decision making process. Since the project involved streaming live images from the camera mounted
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on the device to the remote user, a high data rate was essential. Also the range had to be sufficiently large
so that the user could be at a safe distance from the area of surveillance. From Table 9, it was determined
that Wi-Fi offered the best data rate and range in comparison to all the other technologies under
consideration. The network topology was not of a concern as each device would have its own command
center, so the point to hub topology of the Wi-Fi worked in favor of the project. From Table 9, it can also
be seen that the Wi-Fi has the highest power consumption as compared to the other technologies. It has the
highest energy consumption among all the three competing technologies. This limitation was overcome by
using an onboard portable battery pack to power the Network Interface Card (NIC) and the eBox.
5.
Schedule, Tasks, and Milestones
The Gas Bot was designed and built over three months (September-November). There were many
important tasks which were critical to the timely completion of the project. Of all the tasks, the following
three tasks were considered as the most important milestones and were divided among the team-mates as
follows:

CO sensor (testing and calibrating) and mbed interfacing – Enkuang, Robert, Gowtham

eBox OS creation, GUI, Wi-Fi, serial port and console window integration – Saurabh

Battery Pack, Safety Kit, Glass Stand, OS rebuild and Navigation – Amrinder, Anurag
For the complete schedule, please refer to Appendix A. Appendix B contains the Gantt chart outlining
the entire schedule.
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6.
Results and Acceptance Testing
CO Gas Sensor Calibration
The set up for testing the sensor was that the CO gas sensor had to be first calibrated using a
personal computer or eBox. Since the eBox provided different voltage levels from that of a personal
computer, every time the CO sensor powered up from a computer, either an eBox or a PC, the sensor had
to be recalibrated. The method to calibrate the CO gas sensor was that both potentiometers R3 and R4 had
to be set to 0.8 V. The voltage for R3 was adjusted using the R3 potentiometer (set point) and the voltage
for R4 was adjusted using the R4 potentiometer (trip level). The basic PCB layout of the CO sensor is
shown in Figure 16.
Figure 16. PCB layout of the CO gas sensor.
CO Sensor Test Methods
Four different methods for testing were conducted for the CO gas sensor:

Butane hair curler

Butane lighter

Car exhaust pipe

CO canister
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The ppm values for each of the devices generated from the CO gas sensor are provided in Table 10.
The first three testing devices produced ppm values that fluctuated constantly. Thus, these devices did not
provide relevant data for testing the CO gas sensor. Only the CO canisters provided a constant ppm value
that was appropriate for testing. The CO canisters were provided by the Environmental Health and Safety
(EHS) department of Georgia Tech.
Table 10. PPM Values Generated from CO Gas Sensor for Each Testing Method
Testing Device
PPM Values
Butane Hair Curler
Butane Lighter
50 ppm to 130 ppm
30 ppm to 80 ppm
Car Exhaust Pipe
60 ppm to 150 ppm
36.1 ppm CO Canister
50 ppm CO Canister
38 ppm
58 ppm
Initial Test
The CO gas sensor was initially tested with the butane hair curler. The goal for this test was to see
whether or not the ppm value and Vout for the CO gas sensor increased when the hair curler was placed
next to the sensor. This test verified whether or not the code and the connections for the CO gas sensor
were correctly made.
eBox Test
To test whether the eBox and its drivers were fully functional, several steps had to be conducted:

eBox was able to turn on with power provided from the iRobot Create

The remote user could connect to the eBox via wireless internet

iRobot movement could be controlled by the user using a remote computer

Camera view could be seen at the remote computer
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CO Sensor Intermediate Test
After confirming that the sensor was capable of detect different voltage and ppm values, a more
appropriate test was conducted: test with the CO canisters from the EHS department. EHS department
provided two different CO canisters: 36.1 ppm and 50 ppm canisters. The department also had their own
CO gas detectors that were used to compare with the sensor from Gas Bot. The values from their detector
and the Gas Bot CO gas sensor were compared and are shown in Table 11.
Table 11. PPM Value Comparison and Percent Error
Listed PPM EHS Gas Bot % Error
36.1
35
38
8.57 %
50
54
58
7.41 %
As seen from Table 11, the percent errors for the Gas Bot were 8.57 % for the 36.1 ppm canister
and 7.41 % for the 50 ppm canister. Both percent errors were within the acceptable range of 10 %.
Therefore, the percent error shows that the Gas Bot CO sensor is capable of providing reasonable ppm
values when compared to commercial CO gas detectors.
Full Integration Test
After combining the CO gas sensor to the eBox and the iRobot Create, the ppm values were
successfully transmitted to the eBox via a serial breakout board. Since the eBox provided different DC
voltage from that of a personal computer, the sensor had to be recalibrated when connected to the eBox.
The purpose of this full integration test was to show that the CO gas sensor was able to transmit the ppm
data to the eBox, and the eBox was able to send the values to a remote user via wireless internet
connection.
Final Test
The final test was conducted in the Van Leer building on December 7, 2010, where wireless
internet was accessible. The remote user was able to demonstrate all the proposed requirements by
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navigate the Gas Bot, see the camera view, and read the ppm values at different locations. The Gas Bot
achieved all the objectives that were defined in the proposal.
7.
Budget and Cost Analysis
Table 12 shows the originally planned equipment cost. The predominant portion of the total cost
was due to the CO sensor and the safety box. The total product cost for the Gas Bot, which is shown in
Table 13, is $142.98. The Logitech Pro 9000, eBox 3300 Standard, iRobot Create, mbed microcontroller,
and glass stand have been provided by James Steinberg. Since a majority of parts and products were
provided, $265.56 was saved.
Table 12. Original Plan Equipment Cost
Product Description
Quantity
1
Parallax CO Gas Sensor Module [13]
1
Logitech Pro 9000 [14]
1
eBox-3300 Standard [2]
1
iRobot Create [5]
1
Product Cost Total
Phidgets Interface Kit [12]
Unit Price
$58.45
$29.99
$40.00
$150.00
$129.99
Table 13. New Equipment Cost
Product Description
Quantity
Unit Price
mbed Microcontroller [16]
1
$60.00
Parallax CO Gas Sensor Module [13]
1
$29.99
Logitech Pro 9000 [14]
1
$40.00
eBox-3300 Standard [2]
1
$150.00
iRobot Create [5]
1
$129.99
Safety Box
1
$30.00
Glass Stand
1
$2.00
Voltage Regulator
1
$26.00
Connecting Wires
1
$15.00
Gas Mask
1
$14.99
Butane Hair Curler/Torch
1
$27.00
Product Cost Total
1
$524.97
Price
$58.45
$29.99
$40.00
$150.00
$129.99
$408.44
Cost
$0.00
$29.99
$0.00
$0.00
$0.00
$30.00
$0.00
$26.00
$15.00
$14.99
$27.00
$142.98
Table 14 presents prices of competitors for CO detectors and monitors. The significant differences
in prices are mostly due to the monitor’s ability to sense gases other than CO and the ability to determine
Gas Bots (ECE4007L03)
23
the lower explosive limit (LEL). The LEL is the lowest concentration of a gas or vapor in air capable of
producing a flash of fire in presence of an ignition source. Adding gas sensors such as O2, H2S, and CO2
along with an LEL detector to the Gas Bot will make it more competitive with the high end gas monitors.
However, what makes the Gas Bot unique is the ability to control it wirelessly. The gas monitors listed in
Table 14 are either handheld or stationary devices. Since the Gas Bot only detects CO, it must be
compared to the GAXT and the AW which are priced at $265 and $741 respectively. Thus a rough range
for sale price of the Gas Bot could be from $550 - $800. Addition of more sensors and LEL detection
could change the sale price to around $2,000 (compared to iTX, and iBrid). The Gas Bot’s ability to be
controlled remotely could increase its demand along with the sale price.
Table 14. Competitor Prices
Product
Industrial Scientific iTX LEL/O2/CO Monitor (iTX) [17]
BW Technologies GAXT-M-DL Carbon Monoxide Monitor (GAXT) [18]
Industrial Scientific AIRAWARE-11010 Carbon Monoxide Monitor (AW) [19]
Honeywell Lumidor MicroMax Pro Multi Gas Monitor LEL, O2, Co, H2S (MM)[20]
Industrial Scientific MX6 iBrid LEL, CO, O2, CO2 Monitor (iBrid) [21]
Gas Bots (ECE4007L03)
Price
$1,668.00
$265.00
$741.00
$1,791.00
$2,344.00
24
8.
Conclusions and Future Work
The Gas Bot is a device that can be used by emergency personnel during gas leak crisis to
measure the toxicity levels and provide first aid to individuals trapped in the gas leak area. The Gas
Bot is currently able to send live video feed and CO concentration levels (in ppm) to the controller.
The sensor will continuously send carbon monoxide concentration levels to the controller. The safety
kit will contain emergency assistance materials such as gas masks and walkie-talkies to assist people
who are trapped in the gas leak area. All the initial goals defined in the beginning of the semester were
met by the final product. To further optimize and enhance the usability and marketability of the Gas
Bot, the following additions could be made

Addition of more toxic gas sensors

Use of more accurate and precise sensors

Test in different simulation environments and modules

Implement a rotating platform for the camera for a 360 degree view

Use a Net-book instead of a eBox for faster processing and simpler interfacing

Replace the iRobot platform with a faster and more robust car
Gas Bots (ECE4007L03)
25
9.
References
[1]
H. Laurence, “Carbon monoxide kills about 500 people per year,” The Roanoke Times. Aug.
2006. [Online]. Available: http://www.roanoke.com/news/special/wb/79904. [Accessed:
September 15, 2010].
[2]
DMP Electronics Inc. “eBox the Mini Green PC,” compactpc.com. [Online]. Available:
http://www.compactpc.com.tw/ebox-3300.htm. [Accessed: September 17, 2010].
[3]
Logitech Inc. “Webcam Pro 9000,” logitech.com. [Online]. Available:
http://www.logitech.com/en-us/webcam-communications/webcams/devices/6333. [Accessed:
September 17, 2010].
[4]
Parallax. “CO Gas Sensor Module,” 27931 datasheet, Mar. 2009.
[5]
iRobot Corporation. “iRobot: Roomba Robots,” irobot.com. [Online]. Available:
http://store.irobot.com/category/index.jsp?categoryId=3334619&cp=2804605. [Accessed:
September 5, 2010].
[6]
"Measuring Air Quality: The Pollutant Standards Index," Office of Air Quality Planning and
Standards, Us Epa; Epa 451/k-94-001, Feb. 1994, [Online]. Available:
http://www.air.dnr.state.ga.us/information/co.html. [Accessed: September 16, 2010].
[7]
George, D.. "ICC Strengthens CO, Smoke Detector Codes.” Security Dealer &
Integrator 1 Jan. 2010: ABI/INFORM Trade & Industry, ProQuest. Web. 19 Sep. 2010.
[8]
M.S. Gast, 802.11 Wireless Networks: The Definitive Guide, Second Edition, Sebastopol: O Reilly
Media, 2005.
[9]
D. Gislason, Zigbee Wireless Networking, First Edition, Newnes, 2008.
[10]
Bluetooth.org, “Get Technical: A Brief Overview of Bluetooth,” [Online], Available:
http://www.bluetooth.com/English/Technology/Pages/default.aspx [Accessed Sep 17 2010].
[11]
J.O. Hamblen, Introduction To Embedded Systems Using Windows Embedded CE. 2nd ed.,
Atlanta: Georgia Institute of Technology, 2008, p. 102.
[12]
Robotshop Distribution Inc. “Phidgets relay interface kit,” robotshop.com. [Online]. Available:
http://www.robotshop.com/Phidgetss-1014-relayinterface.html?utm_source=google&utm_medium=base&utm_campaign=BingShopping.
[Accessed: September 18, 2010].
[13]
Robotshop Distribution Inc. “Parallax CO gas sensor module,” robotshop.com. [Online].
Available: http://www.robotshop.com/parallax-co-gas-sensormodule.html?utm_source=google&utm_medium=base&utm_campaign=BingShopping.
[Accessed: September 18, 2010].
Gas Bots (ECE4007L03)
26
[14]
Ebay Inc. “Logitech Quickcam Pro 9000 Web Cam,” ebay.com. [Online]. Available:
http://compare.ebay.com/like/150495915613?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id
=143576388232&crlp=1_240251_263652&UA=WXI8&GUID=36b5353f12b0a0aad4252515f
efe260a&mt_id=572&query=%7Bquery%7D&fitem=150495915613&kw=%7Bquery%7D&ff
4=240251_263652. [Accessed: September 21, 2010].
[15]
ECE 4180. “FireFighter Robot – Project,” ece.gatech.edu. [Online]. Available:
http://users.ece.gatech.edu/~hamblen/489X/F09PROJ/FireFighter_Robot/project.html.
[Accessed: September 15, 2010].
[16]
Robot Shop. “mbed microcontroller,” robotshop.com . [Online]. Available:
http://www.robotshop.com/mbed-rapid-prototypingmicrocontroller.html?utm_source=google&utm_medium=base&utm_campaign=jos.
[Accessed: September 15, 2010].
[17]
Professional Equipment. “Industrial Scientific ITX Multi Gas Monitor,”
professionalequipments.com. [Online]. Available:
http://www.professionalequipment.com/industrial-scientific-itx-multi-gas-monitor-lel-o2-co18104307-11100/multi-gas-meters/?source=pegs. [Accessed: November 15, 2010].
[18]
Inspect USA. “Gas Alert Extreme CO Detector,” inspectusa.com. [Online]. Available:
http://inspectusa.com/alert-extreme-detector-gaxtmdl-01000ppm-sensor-p-1415.html.
[Accessed: November 15, 2010].
[19]
Drill Spot. “Carbon Monoxide Monitor,” drillspot.com. [Online]. Available:
http://www.drillspot.com/products/330374/Industrial_Scientific_AIRAWARE11010_Carbon_Monoxide_Monitor?s=1. [Accessed: November 15, 2010].
[20]
Professional Equipment. “Honeywell Lumidor MicroMAX Pro Multi GasMonitor,”
professionalequipment.com. [Online]. Available:
http://www.professionalequipment.com/honeywell-lumidor-micromax-pro-multi-gas-monitorlel-o2-co-h2s-mpro-4abcd/multi-gas-meters/?source=pegs. [Accessed: November 15, 2010].
[21]
All Safety Products. “Industrial Scientific MX6 iBrid Multi-Gas Monitor,”
allsafetyproducts.com. [Online]. Available:
http://www.csnstores.com/asp/superbrowse.asp?clid=1064&caid=&sku=AKJ1023&refid=FR4
9-AKJ1023. [Accessed: November 15, 2010].
[22]
Hanwei Electronics Co, Ltd. “MQ-7 Gas Sensor,” MQ7 datasheet, Aug. 2010.
Gas Bots (ECE4007L03)
27
Appendix A: Project, Schedule, Tasks, and Milestones
Project Management
Tasks Name
Duration
Team Building and Basic Planning
8/24/2010
2
8/26/2010 Low
Initial Planning Stage
Market Research and Design Optimization
Final Design and Component Acquisition
8/26/2010
9/9/2010
10
6
9/5/2010 Low
9/15/2010 Low
Setting up components to perform individual tasks
Connect eBox to Laptop through Wi-Fi
Create Console to print Serial Data
Send Instructions to move car using eBox
Receive video from Camera to eBox
Mount Sensors on the breakout board
Connect Sensor to mbed Board
Connect mbed Board to eBox to receive information
9/16/2010
9/16/2010
9/16/2010
9/16/2010
9/28/2010
9/28/2010
10/8/2010
8 9/24/2010
12 9/28/2010
15 10/1/2010
15 10/1/2010
1 9/29/2010
10 10/8/2010
10 10/18/2010
Low
Medium
High
High
Low
High
High
Integration of individual Part
Design C# based code to send information to laptop
Send instruction to start the camera and make it move
Receive streaming video from camera
Receive real time information from the sensors
Send instruction to start the car and make it move
10/18/2010
10/23/2010
10/28/2010
10/28/2010
10/28/2010
5
5
30
30
30
Medium
High
Milestone
Milestone
Milestone
Project Demonstration
Initial Demonstration
Final Demonstration
10/13/2010
12/7/2010
Gas Bots (ECE4007L03)
End Date
Degree of
Difficulty
Start Date
10/23/2010
10/28/2010
11/27/2010
11/27/2010
11/27/2010
1 10/14/2010 Milestone
1 12/8/2010 Milestone
28
Appendix B: Gantt Chart
Gas Bots (ECE4007L03)
29
Appendix C: Acknowledgements
Dr. Erick Maxwell - Erick.Maxwell@gtri.gatech.edu
Dr. Arthur Koblasz - art.koblasz@ece.gatech.edu
Dr. James Hamblen – hamblen@ece.gatech.edu
ECE 4180 Teaching Assistant
Jennifer Mcwhorter - Fire Safety Specialist - 404-385-7474
Larry Labbe - Campus Fire Marshall - 404-894-2990
Ed Pozniak - Hazardous Material Team Manager - 404-202-8529
Atlanta Fire Station 8 - 404-546-4408
Environmental Health & Safety (EHS) Team - Ryan Linsk - ryan.lisk@ehs.gatech.edu
James Slack – Industrial Design Student – james.slack@gatech.edu
Edgar Jones - edgar.jones@ece.gatech.edu
James Steinberg - js489@mail.gatech.edu
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