Traditional Chinese Practical Heart rate monitor (1): Circuit Design, Parts List & Workshop Prototype Guide

Premium 15,962 credits (=$159.62) · Priced by article length · permanent access after unlock · 1 $ = 100 credits

heart rate monitor(1)A person's heart rate is one of the objective indicators of emotional state, exercise intensity and heart function. However, it is difficult for most people to accurately measure their heart rate at all times. If you wear a heart rate monitor on your body and use ECG electrodes to detect the ECG signal, and after the signal is processed by the monitor, the user can know the changes in his or her heart rate at any time and self-monitor the changes in heart rate.The block diagram of the heart rate monitor is shown in Figure 22-1, which consists of ECG electrodes, amplifier, frequency/voltage converter, voltage control gate, audio oscillator and sounder. alt="32.jpg (18052 bytes)">Figure 22-1The applicable heart rate range of the heart rate monitor (Ⅰ) is (60~160) beats/minute. By adjusting the relevant components in the circuit, the heart rate range when the alarm sounds can be changed within the range of (60~160) times/minute. The width of this heart rate range is designed to be within ±20% of the central value. For example, if the center value is adjusted beyond 100 beats/minute, the heart rate signal range is (80~120) beats/minute. If the heart rate exceeds the upper and lower limits of this range, the instrument will not sound. If the heart rate is within the above range, the instrument will sound an ECG signal. And the beat of the signal sound is the same as the beat of the heartbeat. If the heart rate is exactly the center value of the instrument's preset range, the frequency of the signal sound emitted by the instrument is 2200Hz, and the output volume is maximum at this time; if the heart rate speeds up, the tone becomes higher and the beat speeds up; when the heart rate slows down, the tone becomes low and the beat slows down. When the heart rate speeds up or the heart rate slows down, the instrument output volume decreases. In this way, users can more clearly identify changes in their own heart rate based on changes in the beat, pitch and loudness of the signal sound.Because the instrument needs to be carried around, it should be as small as possible and consume less power. Its supply voltage is 3V and its quiescent current is 150μA.The electrical schematic diagram of the heart rate monitor (Ⅰ) is shown in Figure 22-2. For the convenience of analysis, the circuit is divided into four parts A, B, C, and D. Part A circuit is an ECG signal amplifier, and the ECG signal waveform picked up by the ECG electrodes is shown in Figure 22-3. Among them, the highest amplitude is about 1mV, and the pulse with the steepest change is called R wave. There are also P wave and T wave that change more slowly. There is an R wave for every heartbeat.The ECG signal is taken out from the electrodes attached to the human body and sent to the input circuit from terminals 1 and 3 (see Figure 22-2). …

Sign in to unlock

Login / Register

One-time payment per article, billed in credits (1 $ = 100 credits). You will review the invoice and the non-refundable digital-asset policy before anything is charged. The PDF is generated on demand and embeds a licensing watermark.