Abstract This paper presents a low cost design of heart beat monitoring device using reflectance mode PhotoPlethysmography (PPG). PPG is known for its simple construction, ease of use and cost effectiveness and can provide information about the changes in cardiac activity as well as aid in earlier non-invasive diagnostics. The proposed device is divided into three phases. First is the detection of pulses through the fingertip. The signal is then passed to the signal processing unit for the purpose of amplification, filtering and digitizing. Finally the heart rate is calculated and displayed on the computer using parallel port interface. The paper is concluded with prototyping of the device followed by verification procedure of the heartbeat signal obtained in laboratory setting. Keywords Reflectance mode PPG, Heart beat detection, Circuit design, PCB design I. INTRODUCTION eartbeat monitoring device (HBMD) is an electronic tool that detects physiological parameters and converts to usable heart rate reading. Heart rate is the number of times the heart beats in a minute and it is produced via depolarization at the sinoatrial and atrioventricular nodes in the heart. The use of HBMD has evolved since its first invention. Monitoring of heart rate has become a common tool in the clinical domain because it appears sensitive to both physiological and psychological disorders. Initial use of HBMD was for clinical applications as a tool in diagnosis, prognosis and management of patients with health problem [2], [3]. The development and usage of the HBMD has taken place rapidly in other areas such as sports and also as heart rate variability (HRV) training device [4]-[6]. For example, the shape of the heart beat waveform reflects arterial changes correlated with hypertension. In addition, HRV training offers promise for the treatment of migraine, reduces asthma severity followed by improvement in cases of diabetic ulcer and frostbites. Furthermore, monitoring of human sexual arousal would contribute remarkably towards the analysis and treatment of sexual dysfunctions [6]. N.I. Ramli is with the School of Engineering, Design and Technology, University of Bradford, BD7 1DP UK and on study leave from Universiti Tun Hussein Onn Malaysia (UTHM), 86400 Parit Raja, Batu Pahat Johor MALAYSIA (e-mail: N.I.B.Ramli@bradford.ac.uk). M. Youseffi is with the School of Engineering, Design and Technology, University of Bradford, BD7 1DP UK (e-mail: m.youseffi@bradford.ac.uk). P.D. Widdop is with the School of Engineering, Design and Technology, University of Bradford, BD7 1DP UK (e-mail: P.D.Widdop@bradford.ac.uk). Pulse oximetry, electrocardiography (ECG) and blood pressure monitor are amongst a few medical devices that display heartbeat reading digitally. However, the only medical device nowadays that extracts heartbeat signals and displays it in graphical form is the electrocardiography (ECG). Common problems with the ECG method is too many sensors and cables connection, fluctuations in the ECG signal baseline, drift, power line noise, motion artifacts due to electrode movement and electromyographic (EMG) interference due to muscular activity. Furthermore, ECG is not suitable for burn victims and continuous monitoring may not be tolerable and the conduction gel used may cause discomfort and inflammation to the skin. In this paper, low cost design of heart beat monitoring device (HBMD) is proposed. The design employ reflectance mode photoplethysmography (PPG) to extract the pulse signal from the finger which is equivalent to the heart beat. The prototype consists of several stages to amplify, filter and digitize the extracted heart beat. Finally, interfacing technique via parallel port to computer is used to calculate and display the heart rate. The device will be simple to use and cost effective. II. RESEARCH OVERVIEW A. Normal Heart Rate Generally, heartbeat can be felt at locations where large arteries are close to the surface of the body. The rate of heartbeat is measured in beats per minute (BPM). Normal heart rate may be indicated by the state of the natural pacemaker, SA node and the state of the conduction pathways. During resting, an infant rate of heartbeat ranges around 130- -130 beats per minute and an older child's about 90-110 beats per minute. Adult's heart rate is about 60-100 beats per minute with average heart rate at about 70 beats per minute for males and 75 beats per minute for females. However, heart rate varies depending on the age and health condition of a person. In a well-trained athletes, it can be significantly low ranging around 40-60 beats per minute [1]. B. Common Methods of Heart Beat Detection Cardiac arrhythmias are often first detected by simple but nonspecific means using a stethoscope or manual feel for peripheral pulses. These cannot usually diagnose specific arrhythmias, but can give a general indication of the heart rate Nur Ilyani Ramli, Mansour Youseffi and Peter Widdop Design and Fabrication of a Low Cost Heart Monitor using Reflectance Photoplethysmogram H World Academy of Science, Engineering and Technology International Journal of Biomedical and Biological Engineering Vol:5, No:8, 2011 307 International Scholarly and Scientific Research & Innovation 5(8) 2011 ISNI:0000000091950263 Open Science Index, Biomedical and Biological Engineering Vol:5, No:8, 2011 publications.waset.org/3628/pdf