Firefighter Life Monitor

Transcription

1 Firefighter Life Monitor By Mary Bucki Seth Groharing Nick Lau Final Report for ECE 445, Senior Design, Spring 2017 TA: Kexin Hui May 3, 2017 Project No. 27

2 Abstract This report chronicles the idealization, design, and refinement of a firefighter life monitor. The firefighter life monitor is a wearable device which tracks the heart rate and internal temperature of a fighter, while checking for motion. All of this data that is collected is transmitted to a display unit through radio frequency (RF). The project involves the design of multiple modular units which include the power supply, the control unit, the sensors, the RF communication circuit, and a display unit. Although there were some design hurdles, the final device is able to track the heart rate, the body temperature, and motion of a person. Future iterations could increase the data transmission range as well increase the transmitters to receiver ratio. ii

3 Table of Contents 1. Introduction Background 1 2. Design Block Diagram Physical Design Power Supply Circuit Design Final Demonstration Sensor Unit Vibration sensor Heart Rate Sensor Temperature Sensor Final Demonstration Control Unit Microcontroller Final Demonstration RF Network RF Transmitter RF Receiver Final Demonstration Display Unit Display Arduino Uno Final Demonstration 11 3 Cost Labor Parts Total 14 4 Conclusion Accomplishments Uncertainties Ethical Considerations Future Work 16 5 References 17 Appendix A 18 iii

4 1 Introduction According to the National Fire Protection Association, approximately 59% of injuries for firefighters are a result of overexertion, stress, and medical difficulties compared to other injuries such as crashes, getting hit by objects, or falling [1]. In 2015, when the National Fire Protection took that data, 90 total firefighters died in the US, meaning 54 lives were lost to overexertion and stress [2]. The goal is to create a device that can monitor heart rate, temperature inside the bunker gear, and motion of the firefighters in the field and send the information to a display unit in another location. The device would be attached to the arm under the firefighter s uniform. This would allow a response team to take appropriate actions if a firefighter was in danger. 1.1 Background Previous projects for firefighters have involved hazard detection and wireless heart rate transmission [3]. Our project would be different in that we are focusing on more than monitoring stress through heart rate. We are also monitoring the temperature inside the firefighter s bunker gear and movement of the firefighter. This device could also be adapted for more than just firefighters in the future, but for our particular problem, the life monitor must work in at least 140 F environments and humid conditions inside a firefighter s bunker gear. 1

5 2 Design: The firefighter life monitor has four main functions: movement detection, temperature reading, heart rate monitoring, and RF transmitting. This is accomplished with a five part modular design consisting of a power supply, control unit, sensor unit, RF network, and display unit. Sensors will obtain the necessary data, the control unit will process this data, and the RF network will wirelessly transmit the data to the display unit. 2.1 Block Diagram: Figure 1. Block Diagram 2

6 2.2 Physical Design: The circuitry must be contained in a light-weight, easy to put on and remove armband. Velcro will be used in order to attach the device to the user s arm. The circuitry excluding the display unit will be housed in nomex, a flame resistant fabric as seen in Figure 3. Figure 2. Physical Design Figure 3. Nomex Armband 3

7 2.3 Power Supply The power supply unit consists of two main components - an alkaline battery source and a voltage regulator. The battery source can be assumed to produce 6±0.5 V. Furthermore, the output voltage required by our system is 3.3±2% V. Figure 4 shows the power supply schematic. Figure 4. Linear Voltage Regulator - LM317[4] Circuit Design The voltage regulator underwent some major changes initially. The original plan was to utilize a buck converter to step down the input voltage to reach the desired output voltage of 3.3V. Due to faulty components, the buck converter was replaced with a linear voltage regulator. The buck converter allows for an adjustable output voltage depending on the output resistor ratio. Benefits for using a buck converter include high efficiency and the ability to a lower input voltage. Assuming all circuit components are selected correctly, the output voltage is given by Equation (2.1) below [5]. The feedback voltage, V FB, is expected to be 0.5V. Equations (2.2) and (2.3) are used to determine capacitors C 1 and C 2 [5]. (2.1) (2.2) (2.3) 4

8 A linear voltage regulator produces an output voltage that is dependent on the output resistor ratio, similar to that of a buck converter. The advantages for using linear voltage regulator in place of the buck converter for this project is the low complexity and the good efficiency. Given that there is a small change from input to output voltage, the wasted power in heat is minimal. Equation (2.4) shows the relationship between the output resistors and output voltage for the linear voltage regulator, LM317 [4]. (2.4) Final Demonstration A multimeter is used to test the power supply unit. The voltage regulator produces 3.28 output voltage, which is well within the output fluctuation range, as seen from Appendix A, Table A1. Utilizing different resistor values, an output of 1.83V can be produced. This output value is also within the output voltage ranges. The 1.8 V output is not utilized after there were design changes to the project. 2.4 Sensor Unit The sensor unit collects data from multiple sensors that are used to monitor the firefighter. Three sensors are used along with appropriate circuitry to process collected temperature, heart rate, and motion detection. Figure 5 shows the original sensor unit design. Our sensor unit PCB did not work, so we had to use off the shelf sensors that provided the same functions as the sensors below. Figure 5. Original Sensor Unit Schematic [6] [7] 5

9 2.4.1 Vibration Sensor A vibration sensor was implemented in order to detect movement of the wearer s arm. We use a vibration sensor rather an accelerometer because a vibration sensor provides a simple alternative to accomplish movement detection. The sensor acts like an open switch when no movement occurs and a closed switch when movement occurs. The switch-like function of the sensor allows for high and low values to be read by the microcontroller. The sensor itself connects from one of the microcontroller pins to ground, and when the sensor is moved the microcontroller pin will read a low value. When no movement occurs the microcontroller reads a high value. Our microcontroller is programmed to look for these high and low values to determine motion. If a low signal is not read after 20 seconds, the microcontroller then transmits that the wearer is inactive Heart Rate Sensor A small heart rate sensor is placed on the user s finger or earlobe to monitor heart rate on the forearm. The sensor sends its data to the microcontroller using an analog signal. The ranges of the heart rate sensor was calculated using Equation (2.5). (2.5) The maximum of the healthy range where heart is being exercised but not overworked during vigorous exercises is given by Equation (2.6). [8] The normal resting heart rate is beats per minute, but during a heart attack, the heart rate is altered due to the disrupted heart flow. The lowest heart rate of our range will be 60 bpm, assuming the firefighter does not have a lower resting heart rate[9]. Firefighter statistics categorized by age group: (3%), (21%), (28%), (26%), (16%), 60 and over (6%) [10]. Based on these statistics, we choose the age range to be years old for the max heart rate, giving us a max heart rate of 180 bpm and the healthy exercising range of 153 bpm for a 40 year old. Thus, our design should test for when the heart rate is outside of bpm, indicative of stress on the heart. The particular sensor used in this project emits infrared light and measures the infrared light reflected back into an infrared sensor. When a pulse is occurring a current spike occurs and the sensor amplifies this signal and sends it to the microcontroller. Figure 6 shows an example of the data that the heart rate sensor is sending to the microcontroller. The red plot represents the analog data being sent and the blue plot represents the BPM, or beats per minute, which is calculated with (2.7) [11]. The value t avg is the average time between pulse peaks. In order to get a more uniform average time in (2.6) 6

10 between the peaks, we took the average of the ten time periods between the peaks. Dividing 60 seconds by that average time gives the BPM. Figure 6. Heart Pulse Graph and BPM (2.7) Temperature Sensor In order to measure temperature we use a thermocouple. A thermocouple is used rather than another method of measuring temperature because thermocouples can withstand higher temperatures. The thermocouple measures the temperature inside the firefighter s bunker gear and sends this data to the microcontroller. As the temperature changes on the thermocouple the data is recorded by a MAX31850K integrated circuit and a 1-Wire protocol is used to send this data to the microcontroller. 7

11 2.4.4 Final Demonstration The vibration sensor responds to movement successfully for movements that changed acceleration directions quickly. This was tested by waving the vibration sensor and confirming that the display showed a binary 1 for motion detection. Slow movements however did not trigger the vibration sensor, but this is allowed by our project because a firefighter would not be using slow movements in the field. The temperature sensor successfully reads temperature, however the IC had trouble with higher temperature over 112 degrees fahrenheit. We tested this by inserting the thermocouple in a warming oven, and it was able to send back good data for temperatures up to 112 degrees fahrenheit. Above that range, the sensor sent a NULL value indicating that the sensor could not send back valid data. The heart rate sensor was tested by placing the sensor on a finger and comparing the heart rate calculated by a simple test of counting the heart beat felt in the user s throat for one minute. The sensor gave back fairly accurate values if the person was not moving, but when movement of the signal wires occurred inaccurate heart rates were given. This could be eliminated if the sensor was placed on the PCB of the microcontroller rather than a separate PCB. In the future we would like to use a different location to measure heart rate as well. We found that the finger gave the most accurate data for our particular sensor, but we would like to be able to measure directly off the arm in the future. 2.5 Control Unit The control unit manages the signals in the circuit and data transmission to the display unit. The control unit only comprises of a microcontroller unit. It also establishes communication between the sensors and the RF transmitter. Figure 7. Control Unit Schematic [12] [13] 8

12 2.5.1 Microcontroller The ATmega328p was selected to control the transmitter side of our circuit. This particular microcontroller is used because it can easily be programmed in C/C++ with the Arduino integrated development environment (IDE) and a USB programmer. The ATmega328p meets the original requirements of supporting serial peripheral interface (SPI) and inter-integrated circuit (I 2 C). The microcontroller also supports the 1-wire library, which is utilized after design changes were made. The microcontroller communicates with the temperature sensor using a 1-wire bus, the vibration sensor with a digital signal, and the pulse sensor with an analog signal. Communication with all the sensors, data processing, and transmission from the RF transmitter are accomplished through the ATmega328p. Figure 8 shows the algorithm of the code programmed to the ATmega328p. The program starts by initializing variables and setting up the sensors. Next one second is allowed to check for motion from the vibration sensor. Without this second the code runs too quickly for a read from this sensor to be done. At this time the code also checks that 20 seconds have not passed since the last movement as to indicate inactivity from the wearer. Finally the data from each sensor is collected into one character array and sent out through the transmitter. Figure 8. Microcontroller and RF Transmitter Flowchart 9

13 2.5.2 Final Demonstration The microcontroller successfully communicates with three sensors through various signals including 1-wire, analog signal, and a binary check for high and low values. 2.6 RF Network The RF Network unit utilizes both an RF transmitter and an RF receiver to transmit collected and organized data from the ATmega328p from the control unit. This enables the transferred data to be read from the Arduino Uno on the display unit and shown on the liquid crystal display (LCD) screen. Wireless communication between the two RF units is accomplished using the VirtualWire library which allows for serial communication on the respective microcontrollers digital pins RF Transmitter The RF transmitter sends data from the microcontroller of the control unit to the RF Receiver. Allows for a display outside the fire to monitor the Firefighter s vitals. A frequency of 434 MHz with a data rate of 2000 bits per second is utilized. Figure 11 shows data that is transmitted to the RF receiver upon collection and organization RF Receiver The Rf receiver receives data from the RF transmitter so that the Arduino Uno can prepare and display the collected data. We used a frequency of 434 MHz at a max data rate of 2000 bits per second. The digital data from the microcontroller is sent using amplitude-shift keying. Figure 10 shows algorithm for the Arduino Uno which also encompasses the functionality of the RF receiver Final Demonstration There was an expected range of approximately 200 feet. However, the design only supported up to about 15 feet before data could no longer be transmitted. This distance was established by testing incremental distances between the RF transmitter and RF receiver. Each time data was collected and sent, the distance between the two unit would increase until the maximum distance was determined. While the maximum transmission distance was small, the communication between the two RF units were functional. A consideration for the minimal distance is the amount of power inputted the transmitter. The project only utilizes the 3.3 volts when the transmitter supports up to 12 volts. If a higher voltage was utilized, then the transmission distance could potentially be amplified. Potential improvements could utilize a boost converter to step up the voltage from the battery supply in order to reach a voltage around 12 to meet the maximum capabilities of the transmitter. 10

14 2.7 Display Unit The display unit will receive data sent from the RF network and output the data on a small screen. It consists of an Arduino Uno and an LCD display. Figure 9. Display Unit Schematic [12][14] Display The display is small LCD display that will simply show the data being sent from the wearable device. It displays the heart rate in BPM, temperature in Fahrenheit, and the motion as a binary 1 (motion detected) or 0 (no motion detected in the last 20 seconds). The LCD will connect directly to the Arduino and uses I2C to receive the data Arduino Uno The Arduino Uno receives the data from the RF network. Figure 10 shows the algorithm for the code programmed to the Arduino Uno. First, variables are initialized and the receiver is set up. Next, when data is received, this data is unpacked and separated into its corresponding values for temperature, heart-rate, and motion. This data is then displayed on the LCD display. It prints the labels of Temp, Heart Rate, and Motion and the respective units. 11

15 Figure 10. Arduino Uno and RF Receiver Flowchart Final Demonstration The display unit was able to display the values corresponding to the values measured by the sensors as seen in Figure 11 with the Appendix table A5 required input of 5V. 3 Cost Figure 11. Display Showing Temperature, Heart Rate, and Motion 12

16 3.1 Labor Table 1. Labor for all the group members Name Hourly Rate Hours Total Cost (Hours x Hourly Rate x 2.5) Nick Lau $ $7,500 Seth Groharing $ $7,500 Mary Bucki $ $7,500 Total 300 $22, Parts Table 2. Total cost of parts Item Manufacturer Part # Quantity Cost $USD Heart Rate Sensor Maxim Integrated MAX30100EFD+- ND Temperature IC Microchip Technology MAX31850KATB+- ND Vibration Sensor Adafruit Thermocouple Wire Digilent, Inc ND Pocket AVR programmer AVR Programming cable SparkFun Electronics ND SparkFun Electronics ND MCU DIP Socket On Shore Technology Inc ED ND MCU DIP Version Microchip Technology ATMEGA328P-PU- ND Arduino Uno Arduino RF Transmitter Wenshing TWS-BS RF Receiver Wenshing RWS pin header Wurth Electronics Inc ND

17 4 pin right angle header Sullins Connector Solutions S5440-ND pin male header Amphenol FCI ND Alkaline Battery Duracell MN1500B4Z Standard LCD 16x2 + extras - white on blue Ada fruit Voltage Regulator Texas Instruments LM3671MF- 3.3/NOPBCT-ND Connector Phoenix Contact ND k Resistor Yageo KGRCT-ND k Resistor Vishay Thin Film ND Resistor Yageo GRCT-ND k Resistor Yageo KGRCT-ND k resistor Yageo KHRCT-ND k Resistor Yageo KGRCT-ND k Resistor Yageo HRCT-ND k Resistor Yageo KHRTR-ND k Resistor Yageo KGRCT-ND k Resistor Yageo KGRCT-ND uF Capacitor Murata ND uF Capacitor Murata ND pF Capacitor Murata ND pF Capacitor TDK Corporation ND pF Capacitor Murata ND pF Capacitor Samsung Electro-Mechanics America, Inc ND nF Capacitor Murata ND uF Capacitor AVX Corporation ND uF Capacitor Kemet ND

18 10k Potentiometer Bourns 3310Y L-ND uH Inductor TDK Corporation ND Ferrite Bead Laird Signal Integrity Products ND Nomex Fabric(60 x60 ) Total parts cost Total Cost Table 3. Total cost Labor $22, Parts $ Total cost $22,

19 4 Conclusion 4.1 Accomplishments High level objectives are achieved but improvements could be made before there are mass productions. The sensor unit was able to track the heart rate in beats per minute, temperature in Fahrenheit, and a binary value for the motion of a person. Through the RF network and display unit, the data was able to be sent, received, and displayed on the display unit at ranges less than 15 feet. The power supply unit was able to output 3.3V with acceptable tolerances. 4.2 Uncertainties There was a time constraint before the final demonstration, preventing the order of a new PCB. Difficulties arose when dealing with buck converters for the power supply unit. Consulting the power electronics TA did not prove to particularly beneficial. There were small design flaws concerning the lack of a heat sink on the sensor unit PCB. Without the heat sink, overheating and frying the sensors was a good possibility, which was heavily avoided. Upon consulting with a TA, there were recommendations to drill holes in the PCB to allow for heat dissipation. Unfortunately, this also did not work. Due to time constraints and a desire to present a finished product at the final demonstration, readily available through hole components and perfboards were used to prepare for the final demonstration. The transmission range through RF could not exceed 20 feet during the best performance and the vibration sensor generally only responded to heavy, excited movements. 4.3 Ethical Considerations It is crucial to take in ethical considerations as mentioned in the IEEE code of ethics because this project deals with the health monitoring of the user. The follow statement correlates with concerns To accept responsibility in making decisions consistent with the safety, health, and welfare of the public, and to disclose promptly factors that might endanger the public or the environment [15]. Our team worked on different blocks to make sure the entire design would work at the end. It is very important for us to communicate efficiently any problems that would endanger the health of the user. 16

20 4.4 Future Work The RF network has room for improvement. RF Error checking should be implemented to make sure that the data sent is correct and not corrupted in transmission. Right now the data is sent in one packet. Perhaps breaking up the packet and sending data from each sensor will help to decrease the error rate of transmission as there are less bits to send per packet. The antenna design can be improved to increase the transmission range of the device. The current part used for the RF transmitter has a maximum input of 12V, so incorporating an output of 12V from the power supply should be able to increase the detection range. Also, the number of transmitters one receiver can communicate with could be increased with proper addressing. Another added feature is to record the data of what happened during the fieldwork. Data that has been collected from the microcontroller could be stored. This data could be used to analyze the amount of stress pressed upon the heart of the individual who was on call. In order to improve the sensor unit, the vibration sensor could be replaced with a more accurate accelerometer. The current vibration sensor only detects movement associated with close to non-zero accelerations. If there is movement with extremely small, or zero, acceleration, then that motion is not detected. The robustness of the heart rate tracking could be improved. Since the firefighter will be moving, a loosely attached heart rate sensor might get disrupted. The final design could be smaller and less obstructive to the firefighter, allowing for the firefighter to carry on with their job without having to worry about moving the health monitor device and disrupting heart rate tracking. Having the final design on PCB would make the final project less costly and more marketable. Another opportunity for this project is to push beyond the scope of only firefighters. With certain modifications, the project could be utilized for policemen or military personnel. Any form of data collection would be beneficial for these groups. Usages range from knowing when to get a person out of a dangerous situation to heavy analysis of what puts the most stress and strain on a person when on the field. 17

21 5 References [1] nfpa.org, Firefighter fatalities in the United States, [Online]. Available: [Accessed: 7- Feb- 2017] [2] usfa.fema.gov, Firefighter Fatalities in the United States in 2015, [Online]. Available: [Accessed: 3- May- 2017] [3] engineering.illinois.edu, Corvae making wireless heart monitoring possible, [Online]. Available: [Accessed: 7- Feb- 2017] [4] LM317 3-Terminal Adjustable Regulator. Texas Instruments. [Online]. Available: [Accessed: 1-Apr ] [5] LM3671/-Q1 2-MHz, 600-mA Step-Down DC-DC Converter. Texas Instruments. [Online]. Available: [Accessed: 20-Feb- 2017] [6] MAX30100 Pulse Oximeter and Heart-Rate Sensor IC for Wearable Health. Maxim Integrated. [Online]. Available: [Accessed: 23- Feb- 2017] [7] MCP9600 Thermocouple EMF to Temperature Converter, ±1.5 C Maximum Accuracy. Microchip Technology Inc [Online]. Available: [Accessed: 24-Feb.-2017] [8] mayoclinic.com, Exercise-intensity, [Online]. Available: [Accessed: Feb. 24, 2017] [9] Fass, Brian. A Heart Rate During a Heart Attack 2011 [Online]. Available: [Accessed: 24- Feb ] [10] firerecruit.com, Top 10 firefighter statistics [Online]. Available: [Accessed: 24- Feb- 2017] [11]pulsesensor.com, Getting Advanced [Online]. Available: [Accessed: 7- Mar- 2017] [12] winavr.scienceprog.com Running TX433 and RX433 RF modules with AVR microcontrollers, [Online]. Available: projects/running-tx433-andrx433-rf-modules-with-avr-microcontrollers.html [Accessed: 23- Feb- 2017] [13] 8-bit AVR Microcontroller. Atmel. [Online]. Available: bit-avr-microcontroller-atmega328pb_datasheet.pdf [Accessed: 23-Feb-2017] [14] learn.adafruit.com Overview [Online]. Available: [Accessed: 22-Feb- 2017] [15] Ieee.org, "IEEE Code of Ethics", [Online]. Available: [Accessed: 7- Feb- 2017] 18

22 Appendix A Requirements and verification Power Supply Component Requirement(s) Verification Voltage Regulators Accepts minimum input of 6 volts Step down to 3.3 ±2% V Step down to 1.8 ±2% V Send 6 volts into each individual voltage regulator Use a multimeter to determine output voltages: 3.3±2% and 1.8 ±2% V Control Unit Table A1. Power Supply Requirements and Verification Component Requirement(s) Verification Microcontroller Communicates with sensors and process the data Run a program through the microcontroller to calculate BPM, Temperature, and detect motion of user. Motion: Cause LED to blink when circuit is moved Heart Rate: Display Serial Data at baud rate and confirm pulse detection and bpm Temperature: Display Serial at 9600 baud rate and confirm correct temperature reading. Table A2. Control Unit Requirements and Verification 19

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24 RF Unit Component Requirement(s) Verification RF Transmitter / Receiver Able to receive data from the RF transmitter at least 200 feet Send data from the transmitter 100 feet away. Verify that the transmitter can receive data 100 feet away Repeat for 150 feet and 200 feet Sensor Unit Table A3. RF Unit Requirements and Verification Component Requirement(s) Verification Vibration Sensor Able to detect when the user moves and sends a notification or signal Move the sensor, verify that it can detect movement with a test led. Leave the sensor motionless. Verify that it can detect no motion with a test led. Temperature Sensor Heart Rate Sensor Can measure temperatures with a maximum 140 F Able to detect heart rate of firefighter with permissible zone of ages during vigorous exercise with a range of beats per minute. Use high heat zone (oven that supports at least 140 F) Verify sensor measures accurate temperature values with serial data or LCD output Place the sensor on finger, induce a heartbeat higher than 153 bpm by exercise, verify that the sensor can detect a range higher than 153 bpm with display serial data Table A4. Sensor Diagram Requirements and Verification 21

25 Display Unit Component Requirement(s) Verification Display Supports 5 volts for operation with a fluctuation of 2% Able to display the English alphabet characters (capital and lowercased) as well as numerical values - character monitor vs graphical monitor Connect a 5v input from a DC supply into the power pins for display unit Connect display unit to a programmable MCU and write small program that displays text written Send English alphabet sentences and numerical values Microcontroller Interface with LCD panel to display user information Can communicate with RF receiver units Load proper LCD drivers with microcontroller Send numerous messages to LCD to test for integrity Connect RF receiver with microcontroller Write program that checks if information is received from receiver Send information from transmitter to receiver and check for functionality Table A5. Display Unit Requirements and Verification 22