Literature Review Initially Research Was Conducted To

Transcript

LITERATURE REVIEW Initially research was conducted to determine the types of vital signs that are routinely measured during a visit to a doctor. These vital signs are: body temperature, pulse rate,blood pressure,etc. As part of our project, we decided to design and build sensors that measure these vital signs. Next, various technologies that were currently used to monitor these vital signs were examined and the most effective sensing techniques for this project was determined. Then we collected data about various wireless communication methods to find a cheap and simple method for the transmission of our signals. 2.1 ECG The Electrocardiograph (ECG) signal is an electrical signal generated by the heart's beating,which can be used as a diagnostic tool for examining some of the functions of the heart. It has a principal measurement range of 0.5 to 4 mV and signal frequency range of 0.01 to 250 Hz. Electrocardiography measures the electrical activity of the heart. Electrical sensing devices or electrodes are placed strategically on top of the body to detect the electrical activity of the heart and diagnose patients with different heart anomalies. The trace depends on the position of the lead. The leads placed on the body can be described as a positive lead and a negative lead. The following figure shows the causes of positive and negative deflections in the heart. Figure 2.1: Causes of deflection The electrical impulse that is generated in the heart travels in parallel to the direction of the lead. If the direction moves toward the positive lead, then a positive deflections takes place, on the other hand, if the direction of the impulse moves toward the negative lead, then a negative deflections takes place. Electrodes are placed in the arms and legs, which are called the Einthoven's triangle. The Einthoven's triangle is composed of Leads I, II, and III. Figure 2.2: Three lead system Einthoven's recording is known as the "three lead" ECG, with measurements taken from three points on the body (defining the "Einthoven triangle" - an equilateral triangle with the heart at the center.) The difference between potential readings from L1 and L2 is what is used to produce the output ECG trace. The L3 connection establishes a common ground for the body and the recording device . Figure 2.3: Typical ecg wave form The first deflections, termed the P-wave is due to the depolarization of the atria. The large QRS-complex is due to the depolarization of the ventricles. This is the complex with the highest amplitude. The last and most significant part for this report is the T-wave. It corresponds to the ventricular repolarization of the heart. 2.2 PULSEOXIMETER Oxygen gas is necessary for human life. It is integral for countless biological processes. The transport of oxygen throughout the human body is performed by the circulatory system, and more specifically, hemoglobin in red blood cells. Critical medical information can be obtained by measuring the amount of oxygen in blood, as a percentage of the maximum capacity. Pulse oximetry has become a standard prcedure for the measurement of blood-oxygen saturation in the hospital operating room and recovery room. Use of light to measure blood oxygen saturation and heart rate is called pulse oximetry. Pulse oximetry relies on measurement of a physiological signal called Photoplethysmography (PPG),which is an optical measurement of the blood volume in arteries .Pulse oximetry acquires PPG signal by irradiating two different wavelengths of light through the tissue and compares the light absorption characteristics of blood under these wavelengths. The comparison leads to a measurement of the oxygenation of blood and is reported as blood oxygen saturation. Figure 2.4: Transmittance and reflectance HEART RATE MONITOR Heart rate measurement of a human being gives the indication in many ways how healthy a person is.It may not be an absolute measure but it denotes the condition and perhaps point out any signs of discrepancies in the cardiovascular system of a person. Most of the heart rate measurement systems are either costly or cannot be reached by normal people. We wanted to design a simple and effective method to monitor the heart rate of a human by noninvasive technique through their fingertip merely by using a LED. Blood flows through our body through the arteries. Our finger tips have finger arteries and our detection principle makes use of this fact. When a source of light,here an LED is employed, is allowed to fall on our finger we could observe that the light reaches the other side through the finger. The light we observe after passing through our finger is varying in its intensity according to the blood ow through our fingers. Since the intensity variation is very minimal we may not actually observe this simple fact. This variation is actually produced by the difference in blood ow through our arteries during heart pulses. If we could convert this minute variation in light intensity into electrical pulses and count them we could easily obtain the heart rate of the person. Figure 2.5: Block Diagram The total implementation of the system can be classified into various sections such as, • Sensor section: It involves the generation of light signals varying with heart pulses and converting it into electrical signals. • Signal conditioning section : It involves the section of system which would process these electrical signals suitably. • Counting section: This part deals with the counting of the electrical pulse fed into the system. • Display section: Part of the system that would show the result in an appropriate manner. BLOOD PRESSURE MONITOR Pressure is the force per unit area and is used to describe fluids in a gaseous or liquid form. At rest, fluid pressure is transmitted equally to all its parts and, at any one point, is the same in all directions. Blood pressure is the pressure that is exerted by blood against the walls of the arteries as it travels from the heart to all parts of the body through the systemic circulatory system. The force needed to circulate this blood is measured in millimeters of mercury (mm Hg) because the traditional measuring device, called a Sphygmomanometer, uses a glass column that is filled with mercury (whose chemical symbol is Hg) and is marked in millimeters. Blood pressure reflects both how strongly the heart is working and what condition the arteries are in. Blood pressure is a function of cardiac output and systemic vascular resistance. The cardiac output is the amount of blood the heart pumps per minute while the systemic vascular resistance is the pressure the walls of the arteries exert on the owing blood. As cardiac output or arterial resistance increases, blood pressure increases accordingly. Blood pressure is commonly referred to in terms of systolic and diastolic pressure. Systolic pressure is the peak pressure reached in the arteries, occurring near the beginning of the cardiac cycle when the ventricles are contracting. Diastolic pressure on the other hand refers to the minimum pressure in the arteries which occurs near the end of the cardiac cycle when the ventricles are filled with blood. The normal blood pressure ranges from 90-119mmHg for systolic and 60-70mmHg for diastolic.If both values are significantly less than 90 or 60mmHg for systolic and diastolic respectively, then the patient may have hypotension (abnormally low blood pressure). On the other hand, if the systolic and diastolic blood pressures are over 120mmHg and 80mmHg respectively, then the patient may have hypertension (abnormally high blood pressure). Figure 2.6: Automatic blood pressure monitor system Oscillometric method is employed for measuring blood pressure. The simplified measurement principle of this method is to measure the amplitude of pressure change in the cuff as the cuff is inflated from above the systolic pressure. The amplitude suddenly grows larger as the pulse breaks through the occlusion. This is very close to systolic pressure. As the cu pressure is further reduced, the pulsation increase in amplitude, reaches a maximum and then diminishes rapidly. The index of diastolic pressure is taken where this rapid transition begins. Therefore, the systolic blood pressure (SBP) and diastolic blood pressure (DBP) are obtained by identifying the region where there is a rapid increase then decrease in the amplitude of the pulses respectively. TEMPERATURE MONITOR Temperature sensors are devices used to measure the temperature of a medium. However,the 3 main types are thermometers, resistance temperature detectors, and thermocouples. Thermometers Thermometers are the most common temperature sensors encountered in simple, everyday measurements of temperature. Two examples of thermometers are the Filled System and Bimetal thermometers. Filled System Thermometer The familiar liquid thermometer consists of a liquid enclosed in a tube. The volume of the fluid changes as a function of temperature. Increased molecular movement with increasing temperature causes the fluid to expand and move along calibrated markings on the side of the tube. The fluid should have a relatively large thermal expansion coefficient so that small changes in temperature will result in detectable changes in volume. A common tube material is glass and a common fluid is alcohol. Mercury used to be a more common fluid until its toxicity was realized. Although the filled-system thermometer is the simplest and cheapest way to measure temperature, its accuracy is limited by the calibration marks along the tube length. Because filled system thermometers are read visually and don't produce electrical signals, it is difficult to implement them in process controls that rely heavily on electrical and computerized control. Bimetal Thermometer In the bimetal thermometer, two metals (commonly steel and copper) with different thermal expansion coefficients are fixed to one another with rivets or by welding. As the temperature of the strip increases, the metal with the higher thermal expansion coefficients expands to a greater degree, causing stress in the materials and a deflections in the strip. The amount of this deflections is a function of temperature. The temperature ranges for which these thermometers can be used is limited by the range over which the metals have significantly different thermal expansion coefficients. Bimetallic strips are often wound into coils and placed in thermostats. The moving end of the strip is an electrical contact, which transmits the temperature thermostat. RF COMMUNICATION RF communication is established using RF module. RF module operates at radio frequency. The corresponding frequency range varies between 30KHz and 300GHz. Transmission through RF is better than IR because of many reasons. Firstly,signals through RF can travel through larger distances making it suitable for long range applications. An RF transmitter generates radio frequency waves in its circuits, and to this carrier signal, it adds the information part by modulating the carrier signal. This composite signal (carrier plus information) is then fed to an antenna (aerial). The aerial induces a corresponding signal into the atmosphere, by altering the Electric and Magnetic fields at (obviously) the same frequency. The impedance of free space is few tens of Ohms to a few hundreds of Ohms. [Impedance may be considered analogous to resistance, but with reactive properties as well.] The power emitted by the transmitter can vary from a megawatt or so (for VLF signals) to a few watts for hand held devices. An Rf receiver Figure 2.7: RF communication block diagram receives the signal from the atmosphere, from its own aerial. The receiver aerial is often quite simple, and the signal level is typically of a few microvolts. This it tunes in (gets rid of unwanted signals and amplifies only the wanted ones). The receiver circuits then strip the information part of the signal from the carrier part, and amplify this to a useful level for audio or video. While IR operates mostly in line of sight mode, RF signals can travel even when there is an obstruction between transmitter and receiver. Next, RF transmission is more strong and reliable than IR transmission. RF communication uses a specific frequency unlike IR signals which are affected by other IR emitting sources. The sensor data in most hospitals are usually transferred through wired networks . There are number of hampering wires from sensors to the data acquisition systems . Now a days many wireless communication solutions are available. Many of these are intended for short range and are reasonably power efficient. It is very useful in BAN (body Area Network) for carrying health information. HARDWARE IMPLEMENTATION To measure the electrocardiogram (ECG), we use this three unipolar leads, placed in Einthoven's triangle configuration. Lead I, Lead II, and Lead III are used. This method works accurately for the scope of this project as it is geared towards older individuals who are less active. different types of temperature sensors were compared and determined that the most effective way of measuring body temperature is by using LM35 temperature sensor. Various ways of non-invasive blood pressure measurement were reviewed. The two main ways blood pressure can be measured are using an oscillometric arm-cu method and Auscultatory method. These methods were compared. This project uses oscillometric method to measure blood pressure. For heart rate measurement we decided to use PPG transmission method. Figure 3.1: Block Diagram ECG We designed an ECG amplifier using an AD620 instrumentation amplifier with gain 500. We use disposable electrodes to take the signal from the human body. 3-Lead electrode placement is used. The average heart rate of a person is around 1.1Hz and the signal level is found to be very weak so a band pass filter is used to avoid interferences from other signals. We obtained a distorted ECG signal. This may due to the frequency distortion, saturation distortion or interference from electric devices and other sources. Using a band-pass filter can easily reject both the DC and high frequency noise but a major source of noise is from electric power system while recording or monitoring the ECG. Electromagnetic interference from nearby high power radio or television can also be picked up by a close loop of lead wires. So to avoid these distortions we have planned to use a battery instead of electric power system, to place a buffer very near to electrodes, etc. Figure 3.2: ECG Design Block Figure 3.3: ECG circuit Electrode and placement selection The first stage in building an ECG monitor is to select the electrodes and determine the placement of these electrodes. For this project disposable electrodes are used. Before attaching the electrodes on the skin, the skin is rubbed and cleaned. A conductive paste is also applied to these electrodes before placing them on the body to reduce the noise in the signal. The paste used for this project is the Ten20 Conductive paste. After the paste has been applied, the electrodes are attached to the skin. Patient cable was used to connect the electrode to the device. For electrode placement, many techniques were reviewed, and the best placement configuration for this project is the Lead I, Lead II, Lead III configuration Figure 3.4: ECG Lead Configuration The Left Arm (LA) and Right Arm (RA) electrodes are placed on the palmer side on the wrists and the Left Leg (LL) and Right Leg (RL) electrodes are placed above the ankle and above the bony ridges. 1. Lead I placement: Right Arm (RA) is connected to the negative input terminal and Left Arm (LA) is connected to the positive input terminal. 2. Lead II placement: RA is connected to the negative input terminal and Left Leg (LL) is connected to the positive input terminal. 3. Lead III placement: LA is connected to the negative input terminal and LL is connected to the positive input terminal. For all these lead configurations, the Right Leg (RL) is referenced as ground. SIGNAL CONDITIONAL CIRCUIT We may obtain the following list of the facts about the signal picked up by the electrodes placed on RA ,LA and LL in the ECG experiment. 1. The magnitude of the R-wave is about 1 - 2 mV. 2. The frequency range of the ECG signal is 0.1 - 250 Hz. 3. Besides the ECG waveform, the signal picked up by the electrodes also contains several kinds of noise: a low-frequency ( <0.03 Hz) noise produced by respiration and electrode movement that results in a base line drift of the ECG signal, an EMG noise which has a wide frequency range (1-5000 Hz), and a 60 Hz noise of power line interference. The magnitudes of these noises are comparable to that of the ECG waveform The basic block diagram of the ECG signal conditioning circuit is Figure 3.5: ECG Signal Conditioning 3.1.2 AD620 instrumentation amplifier In order to enlarge the R-wave to about 0.5 - 1 V, the signal needs to be amplified by an amplifier (or several amplifiers) with a total gain of about 500.For that purpose we are using AD620 instrumentation amplifier. The resistance RG defines the gain of the Figure 3.6: Symbol view of AD620 instrumentation amplifier such that for the input stage of instrumentation amplifier the differential gain is: RG = 49:4K Ohms / G - 1 By letting R G= 100Ω, the gain of the circuit is set to 500. AD620 is a low cost, low power instrumentation amplifier with excellent DC performance and low noise. It is ideal for use in ECG and medical instrumentation. This initial amplification is required to increase the amplitude of the signal so that filtering can be performed. The ECG leads go into the Vin+ and Vin- terminals. The RL ground is connected to the electrical ground 3.1.3 Filter section To remove the low-frequency noise, a high-pass filter can be used. The corner frequency of the filter should be between 0.03 to 0.1 Hz. Since the other two kinds of noise have frequency ranges that are overlapping with that of the ECG waveform, they are more difficulty to remove. The EMG noise can be reduced by requiring the subject to maintain motionless during the measurement. To reduce the 60 Hz noise we use either a high-pass filter with a corner frequency above 60 Hz, or a low-pass filter with a corner frequency below 60 Hz, to reduce the 60 Hz noise. By using either filter, the ECG waveform will also be affected (distorted) because the ECG waveform contains useful information both in the frequency range above and below 60 Hz. The P-wave and Twave mainly contain frequency components that are far below 60 Hz. The R-wave also mainly contains frequency components that are below 60 Hz but it also contains some frequency components that are beyond 60 Hz. Therefore, we decided to use a low-pass filter with a corner frequency below 60 Hz to reduce the 60 Hz noise. Such a filter will: effectively reduce 60 Hz noise, have little effects on P-wave and T-wave, and produce some distortion on the R-wave. So over all filter section is consisting of a low pass filter with cut of frequency 60Hz and high pass filter with cut of frequency 0.03Hz. 3.2 HEART RATE MONITOR Heart beat sensor is designed to give digital output of heat beat when a finger is placed on it. When the heart beat detector is working, the beat LED ashes in unison with each heart beat. This digital output can be connected to microcontroller directly to measure the Beats Per Minute (BPM) rate. It works on the principle of light modulation by blood ow through finger at each pulse. The Heart Beat Sensor provides a simple way to study the hearts function. This sensor monitors the ow of blood through Fifinger. As the heart forces blood through the blood vessels in the Fifinger, the amount of blood in the Fifinger changes with time. The sensor shines a light lobe (small High Bright LED) through the finger and measures the light that is transmitted to LDR. The signal is amplified, and filtered, in the Circuit . Figure 3.7: Circuit Diagram The sensor consists of a super bright red LED and light detector. The LED needs to be super bright as the maximum light must pass spread in finger and detected by detector. Now, when the heart pumps a pulse of blood through the blood vessels, the finger becomes slightly more opaque and so less light reached the detector. With each heart pulse the detector signal varies. This variation is converted to electrical pulse. This signal is amplified and triggered through an amplifier which outputs +5V logic level signal. The output signal is also indicated by a LED which blinks on each heart beat. Algorithm Figure 3.8: Algorithm for heartbeat counter Figure 3.9: Implementation of heart rate monitoring 3.3 BLOOD PRESSURE MONITOR First we collected cu and bulb for blood pressure measurement and pressure sensor (NPC-1220-005).The pressure sensor was checked by noting its output voltage variation according to change in the pressure applied .We observed a raise in output voltage when the cu was inflated and there was drop in output voltage during deflation of cu. The output from pressure sensor was in millivolt range. So an analog circuit was required to amplify both the DC and AC components of the output signal of pressure transducer so that we can use the MCU to process the signal and obtain useful information about the health of the user. Figure 3.10: Overall Circuit Diagram After verifying the pressure sensor we started the designing of the analog circuit. Since the output voltage of the pressure transducer is very small, we had to amplify the signal for further processing. We used the instrumentation amplifier AD620 from Analog Devices. The resistor RG is used to determine the gain of the amplifier according to the equation RG = 49:4K Ohm / G – 1 We chose the resistor RG to be 240 ohms to get a gain of 206.The gain of the AD620 was checked and we got almost correct value. Next the band-pass filter stage was designed as a cascade of the two active band-pass filters. The reason for using two stages is that the overall band-pass stage would provide a large gain and the frequency response of the filter will have sharper cut o than using only single stage. This method will improve the signal to noise ratio of the output. So the device is consisted of three main parts: external hardwares (such as cu, and bulb), analog circuit, and microcontroller. The analog circuit converts the pressure value inside the cu into readable and usable analog waveforms. The MCU samples the waveforms and performs A/D conversion so that further calculations can be made. 3.3.1 Hardware section 3.3.2 Analog Circuit The analog circuit is used to amplify both the DC and AC components of the output signal of pressure transducer so that we can use the MCU to process the signal and obtain useful information about the health of the user. The pressure transducer produces the output voltage proportional to the applied differential input pressure. The output voltage of the pressure transducer ranges from 0 to 40 mV. But for our application, we want to pump the arm cu to only 160 mmHg (approximately 21.33 kPa). This corresponds to the output voltage of approximately 18 mV. Thus, we choose to amplify the voltage so that the DC output voltage of DC amplifier has an output range from 0 to 4V. Thus, we need a gain of approximately 200. Then the signal from the DC amplifier will be passed on to the band-pass filter. The DC amplifier amplifies both DC and AC component of the signal (it's just a regular amplifier). The filter is designed to have large gain at around 1-4 Hz and to attenuate any signal that is out of the pass band. The AC component from the band-pass filter is the most important factor to determine when to capture the systolic/diastolic pressures and when to determine the heart rate of the user. The final stage is the AC coupling stage. We use two identical resistors to provide a DC bias level at approximately 2.5 volts. The 47 uF capacitor is used to coupling only AC component of the signal so that we can provide the DC bias level independently. 1. Pressure Transducer We use the MPX2050 pressure transducer from Motorola to sense the pressure from the arm cu. The pressure transducer produces the output voltage proportional to the applied differential input pressure. We connect the tube from the cu to one of the inputs and we leave another input open. By this way, the output voltage will be proportional to the difference between the pressure in the cu and the air pressure in the room. 2. DC amplifier Since the output voltage of the pressure transducer is very small, we have to amplify the signal for further processing. We use the instrumentation amplifier AD620 from Analog Devices. The resistor R G is used to determine the gain of the amplifier according to the equation RG = 49:4K Ohms / G - 1 Figure 3.11: oscillation signal amplifier Stage Figure 3.12: Schematic of DC amplifier Since we need the gain of approximately 200, we choose the resistor R G to be 240 ohms. This will give us the gain of 206 according to the equation. However, we have measured the gain from the finished circuit, and the measured gain is 213. 3. Concept of Oscillometric method This method is employed by the majority of automated non- invasive devices. A limb and its musculature are compressed by an encircling, inflatable compression cu. The blood pressure reading for systolic and diastolic blood pressure values are read at the parameter identification point. The simplified measurement principle of the oscillometric method is a measurement of the amplitude of pressure change in the cu as the cu is inflated from above the systolic pressure. The amplitude suddenly grows larger as the pulse breaks through the occlusion. This is very close to systolic pressure. As the cu pressure is further reduced, the pulsation increase in amplitude, reaches a maximum and then diminishes rapidly. The index of diastolic pressure is taken where this rapid transition begins. Therefore, the systolic blood pressure (SBP) and diastolic blood pressure (DBP) are obtained by identifying the region where there is a rapid increase then decrease in the amplitude of the pulses respectively. Mean arterial pressure (MAP) is located at the point of maximum oscillation. Hardware description: The filter consists of two RC networks which determine two cut-o frequencies. These two poles are carefully chosen to ensure that the oscillation signal is not distorted or lost. The oscillation signal varies from person to person. In general, it varies from less than 1 mm Hg to 3 mm Hg. From the transfer function of MPXV5050GP, this will translate to a voltage output of 12 mV to 36 mV signal. Since the filter gives an attenuation of 10 dB to the 1 Hz signal, the oscillation signal becomes 3.8 mV to 11.4 mV respectively. 4. AC coupling stage The ac coupling stage is used to provide the DC bias level. We want the DC level of the waveform to locate at approximately half Vdd, which is 2.5 V. Given this Figure 3.13: AC coupling stage for DC bias level bias level, it is easier for us to process the AC signal using the on-chip ADC in the microcontroller. Software Design Figure 3.14: Algorithm for blood pressure measurement 1. Systolic Pressure Measurement After the cu is inflated to a particular value the bulb will be released to deflate the cu . In this deflating state, the program will looks at the AC waveform from ADC0 pin. When the pressure in the cu decreases to a certain value, the blood begins to ow through the arm. The systolic pressure can be obtained at this point. The way we decided to program is that we set a threshold voltage of 4V for the AC waveform. At the start, there is no pulse and the voltage at the ADC0 pin is constant at approximately 2.5 V. Then when the pressure in the cu decreases until it reaches the systolic pressure value, the oscillation starts and grows. We then count the number of pulses that has maximum values above the threshold voltage. If the program counts up to 4, the program enters the Sys-cal state. At this state, the program records the DC voltage from pin ADC1. Then it converts this DC voltage value to the pressure in the cu to determine the systolic pressure of the patient. 2. Diastolic Pressure Measurement In this state, the program is still sampling the signal at every 40 millisecond. We then define the threshold for the diastolic pressure. While the cu is deflating, at some point before the pressure reaches diastolic pressure, the amplitude of the oscillation will decrease. To determine the diastolic pressure, we record the DC value at the point when the amplitude of the oscillation decreases to below the threshold voltage. This is done by looking at the time interval of 2 seconds. If the AC waveform does not go above the threshold in 2 seconds, it means the amplitude of the oscillation is actually below the threshold. Figure 3.15: Implementation of blood pressure measurement 3.4 BODY TEMPERATURE LM35 produces a 10mV change in it's output voltage for every unit rise in temperature (in degree Celsius). The damper RC circuit shields the circuit against any electromagnetic sources. The top of LM35 is attached to patient's arm and hence it's output voltage is equivalent to patient's temperature. LM35 has low self-heating and provides an accuracy of -0.25 oC to +0.25 oC at room temperature. Since it's output voltage is proportional to degree Celsius no conversion factor is required. Figure 3.16: Temperature sensor circuit 3.5 RF COMMUNICATION A general RF communication block diagram is shown above. Since most of the encoders / decoders / microcontrollers are TTL compatible, most of the inputs by the user will be given in TTL logic level. Thus, this TTL input is to be converted into serial data input using an encoder or a micro-controller. This serial data can be directly read using the RF Transmitter, which then performs ASK (in some cases FSK) modulation on it and transmit the data through the antenna. Figure 3.17: RF communication circuit In the receiver side, the RF Receiver receives the modulated signal through the antenna, performs all kinds of processing, filtering, demodulation, etc and gives out a serial data. This serial data is then converted to a TTL level logic data, which is the same data that the user has inputed. RF Modules are used in wireless transfer data. Hence they are suitable for remote control applications, as in where we need to control some machines or robots without getting in touch with them (may be due to various reasons like safety, etc). Now depending upon the type of application, the RF module is chosen. For short range wireless control applications, an ASK RF Transmitter-Receiver Module of frequency 315 MHz or 433 MHz is most suitable. 3.6 FTDI Future Technology Devices International, commonly known by its abbreviation, FTDI, is a Scottish privately traded semiconductor device company, specializing in Universal Serial Bus (USB) technology. It develops, manufactures, and supports devices and their related software drivers for converting RS-232 or TTL serial transmissions to USB signals, in order to allow support for legacy devices with modern computers. Figure 3.18: FTDI chip FTDI provides application specific integrated circuit (ASIC) design services. They also provide consultancy services for product design, specifically in the realm of electronic devices. The company's agship product is its FTDI Chip, an integrated circuit which is a common component on electronic devices using microcontrollers, such as the Arduino physical computing platform . 3.7 PIC MICROCONTROLLER The micro-controller we used in this project is PROGRAMMABLE INTERFACE CONTROLLER (PIC16F877A). In this project, two PICs are used, one at the transmitter and other at the receiver. The PIC's used operates at 20MHz and 16MHz at 5V D.C. The PIC16F877A micro controller is available in 40/44 pin packages. It has 5 I/O ports namely PORTA, PORTB, PORTC, PORTD and PORTE. Each port can be selected as an input or output port by using TRIS commands. Out of 40 pins 7 pins are used for its own functions such as VDD, VSS , GND, RESET and CLK. Besides these functions the PIC16F877A can perform many special functions such as RX, TX, ADC etc. The special function registers are the registers used by the CPU and peripheral modules for controlling the desired operation of the device. The registers are implemented as static RAM. There are 3 memory blocks in each of the PIC16F877A devices. The PIC16F877A device have a 13-bit program counter capable of addressing an 8k word 14 bit program memory space and have an 8k word Ã. 14 bits of Flash program memory. is programmed to count the number of units that we are consumed ,output data to the LCD and provides communication through RF module. The PIC has a maximum voltage rating of 5V dc, that which can withstand. So 5V is given at its Vcc pins (32 11). The operation frequency is 20 MHz. so a crystal oscillator is connected to its oscillator terminals (OSC1-13th pin OSC2-14th pin) and grounded through a capacitor of 22F: In this project,the PICs are used for signal analysis, ADC conversion and serial communication. At the transmitter, PIC obtains the input from the heart beat sensors and count the number of heart beats, obtains the output of the blood pressure analog circuit, does the signal analysis and temperature sensor output, convert the voltage output to its corresponding temperature value and obtains the ECG amplifier output . ADC conversion is done on the results obtained after the signal analysis. The digital data is sent serially through TX pin to the RF module. At the receiver, the PIC receives the sent data from RF module and serially transmits it to a PC using MAX232. 3.8 SOFTWARE IMPLEMENTATION We selected MikroC and Real PIC Simulator for programming and simulating the microcontroller. We decided to use MATLAB and Labview tools for displaying the signals and datas. DATA PROGRAMMING The programming language used in LabVIEW, also referred to as G, is a data flow programming language. Execution is determined by the structure of a graphical block diagram (the LV-source code) on which the programmer connects different function-nodes by drawing wires. These wires propagate variables and any node can execute as soon as all its input data become available. Since this might be the case for multiple nodes simultaneously, G is inherently capable of parallel execution. Multi-processing and multi-threading hardware is automatically exploited by the built-in scheduler, which multiplexes multiple OS threads over the nodes ready for executions. GRAPHICAL PROGRAMMING LabVIEW programs/subroutines are called virtual instruments (VIs). Each VI has three components: a block diagram, a front panel and a connector panel. The last is used to represent the VI in the block diagrams of other, calling VIs. The front panel is built using controls and indicators. Controls are inputs-they allow a user to supply information to the VI. Indicators are outputs-they indicate, or display, the results based on the inputs given to the VI. The back panel, which is a block diagram, contains the graphical source code. All of the objects placed on the front panel will appear on the back panel as terminals. The back panel also contains structures and functions which perform operations on controls and supply data to indicators. Collectively controls, indicators, structures and functions will be referred to as nodes. Nodes are connected to one another using wires- e.g. two controls and an indicator can be wired to the addition function so that the indicator displays the sum of the two controls. Thus a virtual instrument can either be run as a program, with the front panel serving as a user interface, or, when dropped as a node onto the block diagram, the front panel defines the inputs and outputs for the given node through the connector panel. This implies each VI can be easily tested before being embedded as a subroutine into a larger program. 3.8.2 Matlab MATLAB is a high-performance language for technical computing. It integrates computation, visualization, and programming environment. Furthermore, MATLAB is a modern programming language environment: it has sophisticated data structures, contains built in editing and debugging tools, and supports object-oriented programming. These factors make MATLAB an excellent tool for teaching and research. It has powerful built-in routines that enable a very wide variety of computations. It also has easy to use graphics commands that make the visualization of results immediately available. Specific applications are collected in packages referred to as toolbox. There are toolboxes for signal processing, symbolic computation, control theory, simulation, optimization, and several other fields of applied science and engineering. 3.8.3 MikroC The PIC is programmed using MikroC which is the acronym for Micro-Controller Operating Systems. It is intended for use in embedded systems. The language used is embedded C. C remains a very popular language for micro-controller developers due to the code efficiency and reduced overhead and development time. Covers low-level control and is considered more readable than assembly. Many free C compilers are available for a wide variety of development platforms. The compilers are part of an IDEs with ICD support, breakpoints, singlestepping and an assembly window. 3.8.4 Real PIC Simulator Real Pic Simulator is a professional pic simulator for Microchip(tm) pic micro controllers. The simulation process is done in real time with user interaction through different visual components. The main goal of this project is SPEED and we can proudly say that this is the fastest pic simulator on the market. The advantages of using this tool:for professionals, companies - while waitting for the PCB prototyping the development of the rmware can be done, more than one developer can work on the same project (board) without the need of an extra development board for PIC hobbyist - you don't have to buy expensive pic emulators and pic debuggers save time - the PIC microcontroller is not easy to debug without the appropriate tools, Real Pic Simulator is the perfect tool for this job All PIC compilers are supported. Real PIC Simulator imports the HEX or the COD resulted from the compilation. Very easy to use, after the HEX file is imported, place (drag and drop) the visual components that you want to use and make the connections. Currently the following visual components are implemented(more to come): • LEDs - turn LED on or UART terminal (software and hardware) • serial communication Analog source • set analog pin values Push button • set inputs high or low • Character LCD - display text on LCD • Keypad - read up to 4x4 keypads • 7 LED segment display - LED display of seven segments • Oscilloscope - digital oscilloscope • Graphic LCD - display graphics on LCD • Buzzer (speaker) - output sound to PC sound card • Function generator - customize input streams • I2C serial EEPROM memory - simulate a 24C64 (8KBytes) serial memory • DS1307 Real Time Clock - read time with I2C protocol 3.8.5 PCB wizard PCB Wizard 3 is a powerful package for designing single-sided and double-sided printed circuit boards (PCBs).It provides a comprehensive range of tools covering all the traditional steps in PCB production, including schematic drawing, schematic capture, component placement, automatic routing, Bill of Materials reporting and file generation for manufacturing. Steps: • • • • The circuit is drawn and converted to layout form using PCB Wizard. The print out of the layout is taken and then it is placed on the copper plate. After that it is ironed and the copper plate is then dipped in the ferric chloride solution for sometime. Ferric chloride will be plated on the essential locations of the plate and necessary holes are made. Figure 3.19: Ecg layout Figure 3.20: Blood Pressure layout RESULTS AND DISCUSSIONS ECG: While building each stage of the ECG signal conditioning circuit, each circuit block was tested. The component values used in the theoretical design of the circuits were not easily available, so components with values within 5 % tolerances were used. Initially, when building the ECG circuit, testing was performed using a sinusoidal wave. The output was verified stage by stage. Due to clipping of the output signal, the second stage amplifier was omitted. The result obtained after modification was an undistorted version of the amplified input signal. The circuit was then used to monitor the ECG signal. To reduce the noise in the obtained signal, the length of the patient cable was reduced. Further noises were introduced by the power line interference. This noise was eliminated by replacing the power supply with battery. It is clear that ECG signal for relaxed and standing positions looks similar to the desired signal and each phase in the cycle is distinguishable and noise free. However, when the level of physical activity increases, the peaks of heart cycle, the R peaks, are not as easily noticeable. Also, when the person is running, a lot of saturation occurs. The signals are noisier during these higher levels of physical activity due to all the motion artifacts. HEART RATE: The heart beat measurement circuit was tested on a subject. The pulse that was generated was too weak. Initially we used LED and photodiode but since the sensing was very weak, we tried with LDR instead of photodiode and were successful after preventing the ambient light being falling onto it. That was achieved using a simple cardboard like covering. It had a large hole through the middle for the individual± finger. On one side, the Red LED was attached and on its opposite side, the LDR was placed to measure the amount of light transmitted through. When the finger is inserted into the hole, the LED shines light on one side and the transmitted light is captured on the other side of the finger. This case reduces the interference from other light sources. The system performed very well under various environment giving good results. We could observe that the pulse count observed on the indication LED of the system is accurate with heart beat. Providing shield from ambient light and reducing chances of mutual movement of finger and the sensor would give even better results. TEMPERATURE MEASUREMENT: LM35 was tested and verified. Then the temperature measurement circuit was tested on a subject. Voltage corresponding to the body temperature was obtained and in the PIC program, it was converted to its corresponding temperature values. BLOOD PRESSURE MEASUREMENT: MPX2010 pressure sensor was used in the beginning but the variations obtained were not proper. Hence the sensor was replaced with NPC-1220-005 pressure sensor with gave better and approximate values of blood pressure. RF COMMUNICATION: The designed circuit to establish RF communication was found to be complicated for serial transmission and reception and hence the encoder and decoder were omitted from the RF module. PIC was connected to the PC at the receiver using serial cable interface. Labview was used to plot the received ECG signal and Matlab was used to display the received Heartbeat, temperature and blood pressure values. we were successfully able to complete the simulations of the signals including the serial communication in REAL PIC SIMULATOR software. Serial communication implementation was successful after a long try. Blood pressure results obtained for different persons are given in the following table:Systolic and diastolic blood pressure obtained using implemented circuit Sariga 119 59 Raju 122 64 Vidya 122 95 Steve 119 65 using digital bp meter Sariga 114 59 Raju 117 63 Vidya 103 55 Steve 130 83 CONCLUSION AND FRAMEWORK The objective of this project was to build a low power, low cost, reliable, non-intrusive, and non-invasive monitoring system that would accurately measure the vital signs. A reliable and continuous vital sign monitoring system targeted towards older individuals has been successfully built. The resulting system was also low in power and cost, noninvasive, and provided real time monitoring. It is also easy to use and provides accurate measurements. Given the scope of this project, the heart rate,blood pressure and temperature measurement circuits accurately measure the heart rate signal and body temperature. This project can be improved and expanded in numerous ways. First of all, the target group for this product can be expanded to include people of all ages. To achieve this, noise resulting from motion artefact's in the signals has to be reduced. The signal conditioning circuits for these sensors were in analog form on breadboards. These were made in Printed Circuit Boards (PCBs) and digital filtering was done further to reduce noise. Some recommendations on future work would be to add the fourth vital sign monitor to this system, which is measuring the oxygen level in the blood. This can be achieved through PPG. In conclusion, with refinements to the design, the Wireless health monitoring system measuring heart rate, blood pressure, and body temperature would make a great competitor against other products that currently exist in the market. PROGRAMS: HEART RATE MEASUREMENT: unsigned char ch; unsigned short DD0, DD1, DD2, DD3; char *text; unsigned short pulse rate,pulsec ount; long int t; void main() { PORTA = 0; // Reset port A TRISA = 0xFF; // All portA pins are configured as inputs TRISB = 0X00; Lcd_Init(); // LCD display initialization Lcd_Cmd(_LCD_CURSOR_OFF); // LCD command (cursor o) Lcd_Cmd(_LCD_CLEAR); // LCD command (clear LCD) text = "counter program"; Lcd_Out(1,1,text); text = "count : "; OPTION_REG.F5 = 1; // Counter TMR0 receives pulses through the RA4 pin OPTION_REG.F3 = 1; // Prescaler rate is 1:1 Lcd_Out(2,1,text); TMR0 = 0; // Reset timer/counter TMR0 delay_ms(500); delay_ms(500); delay_ ms(500); pulsecount = TMR0; pulserate = pulsecount*4; DD0 = pulserate%10; DD1 = (pulserate/10)%10; DD2 = pulserate/100; Lcd_Chr_CP(48+DD2); Lcd_Chr_CP(48+DD1); Lcd_Chr_CP(48+DD0); delay_ms(5); } TEMPERATURE CONVERSION : // LCD module connections sbit LCD_RS at RB4_bit; sbit LCD_EN at RB5_bit; sbit LCD_D4 at RB0_bit; sbit LCD_D5 at RB1_bit; sbit LCD_D6 at RB2_bit; 44 sbit LCD_D7 at RB3bit; sbitLCD_RS_DirectionatTRISB4_bit; sbitLCD_EN_DirectionatTRISB5_bit; sbitLCD_D4_DirectionatTRISB0_bit; sbitLCD_D5_DirectionatTRISB1_bit; sbitLCD_D6_DirectionatTRISB2_bit; sbitLCD_D7_DirectionatTRISB3_bit; ==EndLCDmoduleconnections unsigned char ch; // unsigned int adc_rd; // Declare variables char *text; long tlong; void main() { INTCON = 0; // All interrupts disabled // Pin RA2 is configured as an analog input TRISA = 0x04; // Rest of pins are configured as digital Lcd_Init(); // LCD display initialization Lcd_Cmd(_LCD_CURSOR_OFF); // LCD command (cursor o) Lcd_Cmd(_LCD_CLEAR); // LCD command (clear LCD) text = "temperature"; // Dene the first message Lcd_Out(1,1,text); // Write the first message in the first line text = "temp:"; // Dene the second message Lcd_Out(2,1,text); // Dene the first message ADCON1 = 0x82; // A/D voltage reference is VCC TRISA = 0xFF; // All port A pins are configured as inputs Delay_ms(2000); text = "temp:"; // Dene the third message while (1) adc_rd = ADC_Read(2); // A/D conversion. Pin RA2 is an input. Lcd_Out(2,1,text); // Write result in the second line tlong = (long)adc_rd * 5000; // Convert the result in millivolts tlong = tlong / 1023; // 0..1023 -> 0-5000mV ch = tlong / 1000; // Extract volts (thousands of millivolts) // from result Lcd_Chr_cp(48+ch); // Write result in ASCII format ch = (tlong / 100) Lcd_Chr_CP(48+ch); // Write result in ASCII format ch = (tlong / 10) % 10; // Extract tens of millivolts Lcd_Chr_CP(48+ch); // Write result in ASCII format ch = tlong Lcd_Chr_CP('.'); // Extract digits for millivolts Lcd_Chr_CP(48+ch); // Write result in ASCII format 45 Lcd_Chr_CP('t'); Delay_ms(1); } BLOOD PRESSURE MEASUREMENT:sbit LCD_RS at RD2_bit; sbit LCD_EN at RD3_bit; sbit LCD_D4 at RD4_bit; sbit LCD_D5 at RD5_bit; sbit LCD_D6 at RD6_bit; sbit LCD_D7 at RD7_bit; sbit LCD_RS_Direction at TRISD2_bit; sbit LCD_EN_Direction at TRISD3_bit; sbit LCD_D4_Direction at TRISD4_bit; sbit LCD_D5_Direction at TRISD5_bit; sbit LCD_D6_Direction at TRISD6_bit; sbit LCD_D7_Direction at TRISD7_bit; // // Declare variables unsigned char ch,sys,dia; char *text; unsigned int adc_rd; long tlong,tlong1; void main() { INTCON = 0; // All interrupts disabled TRISA = 0x04; trisb = 0x00; portb = 0x00; ADCON1 = 0x82; // A/D voltage reference is VCC TRISA = 0xFF; // All port A pins are congured as inputs Delay_ms(2000); while (1) { Lcd_Init(); // LCD display initialization Lcd_Cmd(_LCD_CURSOR_OFF); // LCD command (cursor o) Lcd_Cmd(_LCD_CLEAR); // LCD command (clear LCD) text = "bp apparatus"; Lcd_Out(1,1,text); adc_rd = ADC_Read(2); delay_ms(5); tlong = (long)adc_rd * 5000; // Convert the result in millivolts tlong = tlong / 1023; // 0..1023 -> 0-5000mV if(tlong>2300){ 46 portb.f0 = 1; delay_ms(100); portb.f1 = 1; delay_ms(1500); portb.f2 = 1; adc_rd = ADC_Read(2); tlong = (long)adc_rd * 5000; // Convert the result in millivolts tlong = tlong / 1023; // 0..1023 -> 0-5000mV tlong = tlong/18; text = "sys"; lcd_out(2,1,text); sys = tlong / 1000; // Extract volts (thousands of millivolts) Lcd_Chr_cp(48+sys); // Write result in ASCII format sys = (tlong / 100) % 10; // Extract hundreds of millivolts Lcd_Chr_CP(48+sys); // Write result in ASCII format sys = (tlong / 10) % 10; // Extract tens of millivolts Lcd_Chr_CP(48+sys); // Write result in ASCII format sys = tlong Lcd_Chr_CP(48+sys); // Write result in ASCII format delay_ms(700); portb.f3 = 1; adc_rd = ADCRead(2); tlong1 = (long)adc_rd 5000; ==Converttheresultinmillivolts tlong1 = tlong1=(18 1023); ==0::1023� > 0 � 5000mV text = "dia"; lcd_out(2,9,text); dia = tlong1 / 1000; // Extract volts (thousands of millivolts) Lcd_Chr_cp(48+dia); // Write result in ASCII format dia = (tlong1 / 100) % 10; // Extract hundreds of millivolts Lcd_Chr_CP(48+dia); // Write result in ASCII format dia = (tlong1 / 10) % 10; // Extract tens of millivolts Lcd_Chr_CP(48+dia); // Write result in ASCII format dia = tlong1 % 10; // Extract digits for millivolts Lcd_Chr_CP(48+dia); // Write result in ASCII format break; } } } SERIAL COMMUNICATION: void setup _uart(void); void main(void) { unsigned char ch; 47 TRISC=0b10000000; setup _uart(); while(1) { if(PIR1.F5==1) { ch=RCREG; PIR1.F5=0; } if(PIR1.F4==1) { TXREG=ch+48; DELAY _MS(5); } } } void setup_uart(void) { SPBRG=129; TXSTA.F2=1; TXSTA.F4=0; RCSTA.F7=1; RCSTA.F4=1; TXSTA.F5=1; PIR1.F5=0; PIR1.F4=0; } 48