Submission Format for IMS2004 (Title in 18-point Times font)



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.

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 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.

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.

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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.

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Figure 3. Arduino IDE Console.

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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.

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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.

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Fig. 5. UC3906 Battery Charging Circuit

D. PS1221S Sealed Lead Acid Batteries

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.

E. LT1161 Quad High Speed Switch

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 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.

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Fig. 6. LT1161 Power Switching Circuit

F. Acoustic Sensor

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.

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Fig. 7. Acoustic Circuit Schematic

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.

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Fig. 8. Output analog signal of 130D20 with a pSPL of 107.6dB

G. Temperature Sensor

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:

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.

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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.

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Fig. 10. Temperature Sensor Schematic

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 276-0142 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).

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Fig. 11. Smoke Detector schematic

IV. Software Design

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.

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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.

[pic]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. 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 safety-monitoring 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.

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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 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.

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.

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Database Type

|  |Data Name |Description |

|UserAccount.txt |LoginID | User ID |

| |Password | Key |

| |Name | User Identity |

| |Telephone | Contact |

| |Email | Contact |

|  |Administrator | Rights |

|EContact.txt |Name | Contact Identity |

| |Telephone | Contact |

| |Email | Contact |

| |Gateway | Cell Phone Provider |

|  |Priority |Importance |

|SystemLog.txt |EventID | Identifier |

| |DateTime | Data and Time |

|  |EventInfo | Info |

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