Albanian Wizard

Abstract

This paper describes the design of a simple, low-cost microcontroller based heart rate measuring device with LCD output. Heart rate of the subject is measured from the finger using sensors and the rate is then averaged and displayed on a text based LCD.

The LCD of the heart beat monitor shows the beat per minute.The sensor part consists of sensing elements,LDR(light dependent resistor) and LED(light emitting diode),a comparator module,a low pass filter.Heart beat is sensed by the sensing elements and the comparator produces an amplified square wave output.The comparator output is given to a low pass filter and the filter output is fed to one of the digital inputs of PIC 16F877a type micro controller. The micro controller output ports drives the LCD.

This paper describes the design of a very low-cost device which measures the heart rate of the subject by clipping sensors on one of the fingers and then displaying the result on a text based LCD. Advantage of such a design is that it can be expanded and can easily be connected to a recording device or a PC to collect and analyse the data for over a period of time.

Heart rate measurement is one of the very important parameters of the human cardiovascular system. The heart rate of a healthy adult at rest is around 72 beats per minute (bpm). Athletes normally have lower heart rates than less active people. Babies have a much higher heart rate at around 120 bpm, while older children have heart rates at around 90 bpm. The heart rate rises gradually during exercises and returns slowly to the rest value after exercise. The rate when the pulse returns to normal is an indication of the fitness of the person.

Heart rate is simply and traditionally measured by placing the thumb over the subject’s arterial pulsation, and feeling, timing and counting the pulses usually in a 5 second period. Heart rate (bpm) of the subject is then found by multiplying the obtained number by 12. This method although simple, is not accurate and can give errors when the rate is high. More sophisticated methods to measure the heart rate utilize electronic techniques.

Electro-cardiogram (ECG) is one of frequently used and accurate methods for measuring the heart rate. ECG is an expensive device and its use for the measurement of the heart rate only is not economical. Low-cost devices in the form of wrist watches are also available for the instantaneous measurement of the heart rate. Such devices can give accurate measurements but their cost is usually in excess of several hundred dollars, making them uneconomical. Most hospitals and clinics in the UK use integrated devices designed to measure the heart rate, blood pressure, and temperature of the subject. Although such devices are useful, their cost is usually high and beyond the reach of individuals.

We surely have come a long way in technological developments. Who among us would have envisioned a machine that could figure out whether a person was lying or not? There was time when finding this secret was just in hands of mystical beings or God. Isn’t it startling how a machine can read a person’s mind? Inventor of Lie detector called it cardio-pneumo-psychograph. It was a magic box that had the power to peep in one’s mind and figure out who was pilfering jewelry and cash at college boardinghouse. But to future generations and newspaper reading people, this magic box was lie detector, a machine to help a way out of doubtful scientific credentials and dubious ethical aura. In the era that led to birth of scientific industrial management, I.Q. test and time motion study, a group of American Inventors and the social reformers had dreamt of a device that could separate truth from the deception by measuring body responses like pulse rate, blood pressure. One of the early proponents claimed that this ‘mechanical instrument of future’ would replace jury deliberations, conventional police interrogations. It would also lend a hand to government and private companies in weeding out spies, thieves. It would beam in deepest corners of human psyche and advancing works of psychiatrists. But the man behind the invention, John Larson despaired while taking his breaths and called it a Frankenstein’s monster that had sucked 40 years of his life. The persistent as well as unusual grip of the lie detector on American thoughts provided rich material for Lie Detector’s invention. Various cases including that of Torso Murderers, Cleveland, story of Dick Tracy or William James stirred with scientific visions led to invention of lie detector. Earliest antecedents of modern lie detector come from device that used trial by torture or ordeal. During Middle Ages in the Europe, torture was the practice that rooted from theory that stated – an agonizing body could oblige a lying mind to croak the secret out. But in 1730, this method of torture for extracting the truth from a person made an exit and a new lie detection method took over. Daniel Defoe was the earliest of men to suggest such a method through evaluation of heart rate. In 18th century, the torturous methods declined completely due to continuous campaigns against the judicial torture in the Europe. This humane way of detecting lie through lie detector was accepted by majority during this time. The evolution of lie detector was slow but was a pioneering invention for the entire mankind. The emergence started slowly with the initial tests for determining the physical responses during act of deception. Cesare Lombroso also known as Father of the Modern Criminology was the first one to try of application of science for detecting deception. He made use of device known as plethysmograph that monitored changes in blood flow of person at the time of interrogation. Another breakthrough came in the year 1897 with development of method to measure galvanic responses by B. Sticker. This method used amount of sweat produced on skin with the help of electric conductibility during the test. And in 1914, breathing rate measurement using the pneumatic tubing was done by Vittorio Benussi. This device was draped around the person’s chest for measuring the rate and depth of breath. Benussi discovered ratio of expiration and inspiration was usually greater at the time of truth telling than lying. This method of truth discovery by Benussi gave an important revelation that it was not just pulse rate, sweat production and the blood pressure that helped in lie detection but the breathing rates too. All these findings amalgamated together formed the modern day lie detector known as polygraph. Earliest machine that took name of polygraph was originally copy machine invented by John Hawkins in year 1804. Name of the machine simply meant ‘many writings’, originated from Greek, early polygraph allowed users to write with the two pens at the same time, creating duplicate copy. In year 1908, an English doctor named James MacKenzie publicized in ink polygraph invention for monitoring cardiovascular responses of the subject taking blood pressure and pulse. After a few years, in year 1915, William Marston who was American psychologist, started demonstrated lie detection tests to determine whether subject was deceptive using blood pressure cuffs for taking measurements of the systolic BP at the time of interrogation. He was of the strong view that the interrogation techniques used at conjunction with technology than technology itself that led to detection of lies. As lie detector captured imagination of public, imitators soon entered the field. A doctor from Chicago doctor, Orlando Scott, endorsed Thought Wave Detector, with claims that it had the capability of tapping electrical current of brain. While suspect squirmed and sweated, a big needle sung forth and backwards between true and false option on a big dial. Despite of the charlatans like Dr. Scott, lie detector made the headway in search for its respect and acceptance. In year 1923, legal decision barred the tests by lie detectors being used as the evidence in courtroom but at places like factories, government department, banks this magic box carved a place for itself offering an efficient solution for detection. Advertisers too flirted briefly in various tests for finding what consumers thought about their gasoline, cigarettes and razors. Keeping censors in mind, even film executives used the findings for editing of films like Frankenstein. During cold war too, lie detectors were used by State Department for weeding Communist sympathizers out. Lie detectors have proved to be an amazingly useful technology for the world.