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Safety Monitoring Device and
System
Andrew Farrell, Alan Seims, Frank Ogadah and
Tien Tran
School of Electrical Engineering and Computer
Science, University of Central Florida, Orlando,
Florida, 32816-2450 (12 point Times font)
Abstract — With the commercial buildings growing larger
due to increases in population density, the response time of
rescue officials during emergency situations is critical.
Index Terms — Ceramics, coaxial resonators, delay filters,
delay-lines, power amplifiers.
Monitoring Device trigger level for sound can be
adjusted by the end-user to accommodate for the
conditions in certain harsh environments such as in
industrial manufacturing facilities or large commercial
ships. The system is designed to detect fires by two
different means: detecting the smoke from the ignition of
combustibles and measuring the ambient room
temperature for an increase in heat caused by fire. The
system utilizes a photoelectric integrated circuit smoke
sensor, which uses light measurements to detect the
presence of smoke.
The Monitoring System Software is a user-friendly
system whose main purpose is to connect the user to the
safety device through simple means. The GUI will have
red and green indicators to inform the user if the sensors
on the device are in working order.
In addition to
monitoring the device the software will allow for an easy
means of sending out alert messages through text
messaging and emails. The program also restricts access to
specific individuals, there by regulating who is accessing
the system.
I. INTRODUCTION
In 2007 alone, there were over 2772 incidents in the U.S
where incendiary or explosive devices were reported.
When a moderate explosion occurs in a public or private
workplace, lives are taken and property damage is high.
The response time of rescue officials must be very low to
prevent further loss of lives or damage to property. The
Safety Monitoring device is meant to identify and locate
an explosion or fire and relay the information to a central
monitoring system where a graphic user interface allows
the end user to know immediately when and where an
incident has occurred. The system is designed for simple
integration into any building.
A network of Safety Monitoring Devices can be linked
together in a large building by use of the Safety
Monitoring System, which provides central monitoring
computers with information regarding the status of the
network. The network devices alert the central monitoring
system when a fire or explosion has been detected. The
system logs when any device is triggered or disconnected
from the system so that a full account of network activity
is kept.
The system detects an explosion by measuring the room
sound pressure level. When an explosion occurs a pressure
wave containing audible energy waves is sent in all
directions. These waves are picked up by an acoustic
microphone and compared to a set threshold. The Safety
II. SYSTEM COMPONENTS
The Safety Monitoring Device and System, as seen in
Figure 1, is composed of four major parts: the Graphic
User Interface, Controller, Power Management System
and Sensors.
Figure 1. Complete System overview
A. Graphic User Interface
The graphic user interface for the Safety Monitoring
Device and System provides the end user with a means of
monitor and control to the individual detectors and
sensors. The GUI also provides network-alerting
capabilities and records a system log of events.
B. Controller
The gateway between the hardware and software in the
Safety Monitoring Device and System is the Arduino
Atmega 328P controller. The controller allows the users to
individually turn off and on specific detectors and sensors
to prevent false tripping. Asides from controlling which
sensors are being utilized, the controller also processes the
signals from the individual sensors and relays that
information to the end user via the GUI, which is
interfaced through an RS232 or USB connection.
C. Power Management
The Power Management System supplies continuous
power to the device by means of an AC to DC converter.
The voltage is then regulated with LM317 regulators to
supply the individual voltages needed for each sub-circuit.
The sensor’s power is supplied through the LT1161 quad
high-speed switch, which is controlled by the
microcontroller. The Power Management System also
ensures continuous power to the device during a main
power failure by means of a battery backup system. The
battery backup system is comprised of two 12V Sealed
Lead Acid batteries and the UC3906 SLA battery charger
IC, which will give the device the capability of running in
standalone mode.
D. Sensors
The Safety Monitoring Device utilizes three sensors,
which will monitor room temperature, acoustics and air.
The device utilizes a threshold scheme where the end-user
will only be alerted if conditions exceed predetermined
thresholds. Room acoustics will be monitored with a PCB
Piezotronics 130D20 piezoelectric transducer. The Safety
Monitoring Device will only trigger an event if the pSPL
exceeds 100dB. Room temperature monitoring will be
provided by National Instruments LM19 temperature
sensor. The temperature monitoring system will meet
NFPA standards as a “LOW” heat detector with a
triggering threshold of 120°F. Lastly, an Infrared Smoke
Detector Sensor was designed to monitor the air, and by
default has high sensitivity to any type of smoke.
However, the sensitivity can be user defined.
III. HARDWARE OVERVIEW
The hardware selection and design will be discussed to
their entirety excluding the external peripheral device for
which the GUI will be loaded to. The purpose of the
hardware overview will be to illustrate the overall system
stability and functionality.
A. Atmega Arduino 320P Controller
This is a low power, AVR type, 8-Bit high performance
microcontroller. The features include: 32 by 8 general
working registers; 20 MIPS (million instructions per
second) at 16MHz frequency; built in High endurance
Non-Volatile memory segments which are flash, EEPROM
and SRAM which have an estimated 1000 flash write/erase
cycles and 100,000 EEPROM write/erase cycles. The
system also has an optional On-chip boot program. The
main peripheral features are two 8-Bit timer/counters with
separate pre-scalar and compare modes, and one 16-Bit
counter with capture mode. The device comes with an
inbuilt analog digital converter. 8 channels or 10-Bits have
been dedicated to TQFP and QNF/MLF, while 6 channels
have 10-Bit PDIP. The latter mentioned is highly desirable
for this particular design. For design purposes, the chip
possesses a programmable serial USART, which will be
beneficial for programming a RS232 serial I/O device to
be used to transfer data or information from chip to
computer. The latter mentioned was used and
programming was done via serial USART which handled
RS 232 as well as USB for I/O procedures. The
microcontroller receives and processes signals from the
sensors in analog form, converts them to digital and
transmits the processed data to the GUI. For normal
operation the output of the sensors are set and maintained
high, which the microcontroller sees as a positive 5V.
Once an event occurs, the sensor changes status and drops
to a low output. This is seen by the microcontroller as any
voltage less than 4.5 volts. According to Figure 2 below,
the input signals are sent directly to the microcontroller to
pins ADC0 (Acoustic), ADC1 (Thermal) and ADC2
(Smoke). Upon receipt, these signals are converted to
digital signals, and periodically sent to the GUI for online
verification and processing. The microcontroller was
designed to individually control the power to the sensors
by turning them on and off. This is facilitated by use of the
LT1161 Quad Switch. Figure 2 also shows the various pin
connections of the MCU in relation to the sensors, power
supply and transmission lines.
Arduino Chip comes with its own programming code
that is built on the same Platform as C but much more user
friendly. The instructions are straightforward and the chip
is built to respond to these simple commands. As per the
development board, there are pin numbers printed on the
board, which have already been programmed into
Arduino's libraries. Figure 3 shows the IDE for Arduino
and a sample of the pin assignments.
The code was written to receive analog signals, sample
them for any event occurrences and send information to
the GUI. Each sensor is individually sampled to isolate the
events that occur. This also assists in troubleshooting false
alarms and data logging with the GUI. In addition, code
was written to turn on/off sensors and sound an alarm
connected internally to the device. All this information
was sent via USB/RS 232 to the end user, via the GUI, for
further decision-making.
Figure 2: Schematic Diagram for Arduino MCU with
sensors and I/O lines.
B. LS35-36 AC/DC Power Supply
The LS35-36 is a universal power supply that can
convert 88-264VAC, with a frequency range of 47-63 Hz,
into 36VDC and a supply current of 1A. This will enable
the device to be marketed internationally. After conversion
the power is distributed to each sub-circuit’s LM317
adjustable voltage regulator and stepped down to the
circuits required voltage. Figure 4 shows the power
consumption of the device and its sub-circuits.
Figure 3. Arduino IDE Console.
Fig. 4.
Power Distribution Chart
C. UC3906 Lead Acid Battery Charger IC
The Safety Monitoring Device requires battery backup
during a main power failure. The battery backup system
will also give the device the capabilities to work in
standalone mode. To ensure that the battery backup system
not require routine maintenance a proper battery charging
system had to be implemented. This design will ensure
longevity of the Sealed Lead Acid batteries and prevent
them from being overcharged. The UC3906 Battery
Charging IC is designed to be used specifically with SLA
batteries. The IC monitors the battery characteristics and
regulates the charging current to the battery through the
use of an external transistor. Figure 5 shows the battery
charging circuit used.
function allows the user to control the power, being
supplied to the sensors, from the GUI. Figure 6 shows the
switching circuit that controls the power to the sensors.
Fig. 6. LT1161 Power Switching Circuit
F. Acoustic Sensor
Fig. 5. UC3906 Battery Charging Circuit
D. PS1221S Sealed Lead Acid Batteries
The safety-monitoring device utilizes PCB Piezotronics
130D20 piezoelectric transducer. The 130D20 has a
dynamic frequency range between 15 Hz and 15 kHz. The
transducer has a linear response of 1V/Pa to sound waves
up to 130dB, with a 3% distortion in the analog output for
sound pressure waves greater than 130dB.
For proper excitation the 130D20 requires a constant
DC supply voltage between 18-VDC to 30-VDC and a
constant regulated current between 2mA to 20mA. The
excitation requirements are met by having a 1N5314
current regulating diode in series with a 24V regulator as
shown in Figure 7. The 1N5314 manufactured by
MicroSemi Corp, has a nominal current regulation of
4.70mA.
The device must be operational and capable of working
in standalone mode during main power failures. The
device’s backup power will be supplied by two 12V
PS1221S Sealed Lead Acid batteries put in series to
supply the required 24V needed by the device. These
batteries have a storage capacity of 2 Ah, which will give
the device the capability to run in standalone mode for
approximately twenty-four hours.
5Vdc
R4
10k
R3
5k
0
130D20
BNC Connector
1
C1
2
E. LT1161 Quad High Speed Switch
10uF
R1
4.6k
The LT1161 works in conjunction with the
microcontroller to control the power being supplied to
each individual sensor sub-circuit. This is done with the
use of external MOSFETs that act as switches. The
switching of the MOSFETs is controlled by the
microcontroller via the LT116. The LT1161 uses an
internal charge pump to enhance the MOSFET when a
control signal is received from the microcontroller. This
8
AD790
8-DIP
7
3
6
4
5
D1
D1N5314
0
24Vdc Power Supply
Fig. 7. Acoustic Circuit Schematic
Acoustic_Pin
R2
10k
A 10uF electrolytic capacitor couples the AC signal
from the 130D20 and is pulled down to ground by a 4.7kΩ
resistor.
The processing of the signal is done with the use of an
inverting comparator. The objective behind the use of the
inverting comparator is to always have a constant 5-V
output from the circuit so that the microcontroller is
always communicating with the circuit. When an event or
power failure within the circuit occurs the controller will
immediately detect the occurrence and notify the end-user
via the GUI. Analog Devices AD790 was chosen to be the
comparator for the circuit due to its rail-to-rail output
capabilities and fast response time of 7.9ns. The positive
supply rail of the comparator is 5V with the negative rail
being tied to ground. The AD790 compares the voltage
waveform of the 4.7kΩ resistor with a 2V reference
voltage, which corresponds to a 100dB output from the
130D20. Figure 8 shows the analog output of the 130D20
and AD790 when a blast cap was discharged which
produced a pSPL of 107.6dB. The reference voltage can
be tuned by adjusting an external potentiometer, R3, which
will enable the end-user to adjust the threshold for sound
pressure in a room.
Fig. 8. Output analog signal of 130D20 with a pSPL of
107.6dB
VO = (-3.88 * 10-6) T2 + (-1.15*10-2) T + 1.8639
Using the parabolic transfer function the trigger voltage
corresponding to 120 F was determined to be 1.29V.
Fig. 9. LM19 analog voltage output
Figure 10 is the schematic for the temperature sensor
circuit. The supply voltage line is coupled to the ground
pin via a 0.1uF electrolytic capacitor. The output of the
LM19 is pulled to ground by a 4.7kΩ resistor (R3). The
LM2903 voltage comparator is setup in a non-inverting
configuration so that during normal room conditions the
output of the comparator is 5-V but once the temperature
reaches 120⁰F corresponding to an output voltage drop
from LM19 to 1.29-V the output swings to the negative
rail (0-V). The reference voltage for which the temperature
threshold is defined is user definable by adjusting the
value of the potentiometer R2. The purpose behind
allowing the user to adjust the threshold setting is so that
device can be utilized in every room in a building from
normal offices which are air conditioned to manufacturing
lines which can be operating at much higher temperatures.
5Vdc
G. Temperature Sensor
R1
10k
5Vdc
R4
3k
8
R2
0
Vs
Vo
3
+
2
-
C1
LM19
0.1uF
R3
4.7k
gnd
0
Fig. 10. Temperature Sensor Schematic
U2A
1
4
The safety-monitoring device meets NFPA standards as
a “low” heat detector with a triggering threshold by default
of 120 F. National Instruments LM19 CMOS technology
temperature sensor is utilized as the temperature sensor.
The LM19 was chosen for this application since the device
can operate between –55 C and 130 C and it has a fairly
high with a max error of +/- 3.5 C at peak conditions. The
output of the LM19 is shown in figure 9. With a negative
thermal coefficient at normal room temperature (27⁰C) the
output voltage is 1.56V. There are two transfer functions
provided by National instruments, one, which is linear, and
the other parabolic. The parabolic transfer function
provides the most accurate response of the sensor and is
defined as:
LM2903
Smoke_Pin
IV. SOFTWARE DESIGN
H. Smoke Sensor
Monitoring room air for smoke is necessary for
providing a monitoring system that can detect incendiary
events. The smoke sensor utilized in the Safety Monitoring
Device and System is constructed of an infrared emitter
and an infrared detector, which acts as a switch.
The smoke detector circuit is shown in Figure 11. The
infrared emitter and detector packages are model 2760142 from Radio Shack. The emitter has a radiant power
output of 13-15mW and the transmission wavelength of
950nm. The emitter is in series with an 180Ω resistor and
connected to a 5VDC regulator and in the configuration
has a nominal forward voltage drop of 1.6V.
The infrared detector has a peak sensitivity of 850nm
and spectral bandwidth between 620nm to 980nm. Two
3kΩ resistors (R2 and R3) are used to drive the detector
when the gate (infrared sensor) is turned on. The nominal
voltage of R3 when the infrared emitter and detector are
perpendicular to each other and at a distance of 20mm is
1V. A LM2903 voltage comparator is used to measure the
voltage across R3. When smoke enters the space between
the IR detector and IR sensor the intensity detected by the
detector drops which results in the voltage across R3 to
decrease. By testing with Smoke Check Smoke Detector
Test Spray, which meets NFPA 72 standards, UL 217 and
UL 268 standards, we were able to determine a reference
voltage of 0.9 V as our threshold. The sensitivity of the
smoke detector can be increased or decreased accordingly
by adjusting the potentiometer R2. The LM2903 is setup
in a non-inverting configuration so that during normal
conditions the output of the comparator is 5-V, however,
when smoke is detected and the output of the detector
circuit falls below 0.9-V or the users defined threshold, the
output drops low (0-V).
The safety monitoring software is a vital aspect of this
project that links the end-user to the safety device with
minimal difficulty. The program was created using Visual
Studio 2008 in object oriented C#. The software utilizes a
graphical user interface (GUI) to allow for simplified
communications and interaction between the end user and
the safety device. The program also upholds a database
system for data storage of key data to use as records and
operation. An alert system is implemented to distribute
important information to key individuals whenever needed
and the monitoring system provides the keep aspect of
linking the user to the device.
A. GUI
The GUI is broken up into nine forms or windows
mainly concern with its own operations, essentially
running almost independently of one another with each
contained in its own class. Fig. 12 depicts the GUI layout
and how each form connects with one another. The
Password form is designed to check users accessing the
system ensuring that the correct individuals gain access to
the system. The form simply verifies user name and
password by matching the entered data to the one stored in
the database. After account verification, the user gets
access to the main form or the hub of all the other
programs.
5Vdc
R1
10k
5VDC
R4
3k
R2
C 1
3k
0
3
E 2
2
+
U2A
1
Smoke_Pin
-
R3
3k
4
3 A
R1
180
U2
8
R2
4 K
LM2903
R3
4.7k
Fig. 11. Smoke Detector schematic
Fig. 12. - GUI Layout
The System Log form lets user view passed events that
have occurred during the programs run time, which is
automatically updated periodically through code. The
Emergency Contact form and User Account form are
admin specific; meaning only accounts with administrative
rights can gain access to them. The window allows for
viewing and editing of database information of user
accounts and emergency contact information used in the
alert aspect of the program. The Monitor and Alert form
are the most vital allowing the user to connect to the safety
device as well as send out important messages as needed.
B. Database
The software's database contains sets of data variables
shown in fig. 13 that provides necessary information
during the programs operation. Each set of data is held
within their own text file stored on the hard drive with
specific data important for each set. The database consists
of three files each consisting of its own data set.
UserAccout.txt holds user information that determines
the current user access the system. The LoginID is the
user's ID, Password is their key, Name is the user's true
Identity, and Telephone and Email are ways to contact
them outside of the program. The Administrator is a
Boolean for determining if the user has admin rights for
modifying certain data.
DATABASE TYPE
UserAccount.txt
EContact.txt
SystemLog.txt
Data Name
LoginID
Password
Name
Telephone
Email
Administrator
Name
Telephone
Email
Gateway
Priority
EventID
DateTime
EventInfo
Description
User ID
Key
User Identity
Contact
Contact
Rights
Contact Identity
Contact
Contact
Cell Phone Provider
Importance
Identifier
Data and Time
Info
Fig. 13. Database Types
EContact.txt contains the contact information of
individuals that needs to be alerted if the system has
detected a problem. Name is the contacts label and
Telephone and Email are ways used to contact them. The
Gateway is a key variable that is used to identify what cell
phone provider the Telephone number that was saved is
part of. This allows for the program to set the sms
messages accordingly. The Priority variable just
determines the order in which information is distributed.
The SystemLog.txt case recorded information for
certain events that occur during the programs operations.
These events include successful and unsuccessful attempts
to log into the system as well as when and what sensors
have tripped on the device when the program is monitoring
the safety device. EventID is an identifier, DateTime is the
exact date and time the event occurred, and EventInfo is a
brief description of the event.
C. Alert System
The Alert form or window handles necessary procedures
for sending out necessary information to important
contacts stored in the EContact data set. The two methods
of alerting contacts are emailing and short message service
(sms). The form requests a topic and a body before
beginning the alerting process. The process of distributing
the information to specific email accounts and cell phones,
which is done using a mail server.
For the purposes of demonstration, Google's Gmail
server will be used, which has an smtp at smtp.gmail.com
and port number 587. For sms, the sent address of the cell
phone number and the phone provider must be present in
order for text messages to go through. Messages will be
sent out through priority system of three tiers of
importance. If the contact meets the first tier, the message
is sent out to them on the first loop of the data sets, and so
on for the second and third tier. This is so information is
sent out important individuals as quickly as possible.
D. Monitor System
The Monitor form shown in fig. 14 depicts the main
interface for which the user will interact with the safetymonitoring device. This form allows the user to connect to
the device and when a connection is established new
options will be enabled for control over the device from
the GUI; these include turning off individuals sensors and
resetting them. The form also displays the device's status
both through text and images.
2008. His interests include programming MCU,
Signal.Processing using LabView and Control Systems
using MathLab.
Alan Seims is a senior at the University
of Central Florida. Alan will receive his
Bachelor’s of Science in Electrical
Engineering in August of 2009. Alan
gained experience as an avionics
technician in the United States Air
Force and plans on pursuing a career in
the alternative energy field.
Fig. 14. Main Interface
Connection to the device is done by scan for all
available connections and ping each then waiting for a
response. If nothing is returned the method continues to
the next port till all connections are exhausted or a
connection is made. When a connection is established the
code sends out a request for each sensor's status. The
response will be reflected in the images on the form for
each sensor. This sensor check will occur every time a
change is made to the system from the GUI. If a message
is received from the device that a sensor is tripped a
message will be displayed accordingly and the sensor
images will change as such from Green to Red.
REFERENCES
Tien Quang Tran, a senior student
of
the
computer
engineering
department at the University of
Central Florida. He is pursuing a
working
career
in
computer
engineering, while pushing for a
master's degree in the field.
Frank Ogadah-Oyugy is currently a
senior in the University of Central
Florida and will receive his Bachelor
of Science in Electrical and computer
Engineering in Spring 2010. He has
attended University of Central
Florida now for 3 years as a transfer
student, plans to pursue his Masters in summer of 2010.
Recently worked for Novacomm Security Systems Inc.
(Spring/Summer 09) and worked for AT&T in Summer
Andrew Farrell, a senior Electrical
Engineering student at the University
of Central Florida. He is currently
working
for
Electrodynamics
Associates, Inc as an intern with a
focus on controller design and
implementation. Upon graduation,
he will be pursuing his Masters in
Electrical Engineering with a focus
in control systems at the University of Central Florida.