Although the wearable market has not yet erupted, it is an indisputable fact that it will set off an explosive frenzy in the electronics industry in the future, and wearables will be one of the first applications to break through.
More medical design and hot technology, high-level views, and new and interesting technology and engineers' experience that you are interested in, all in September, "Smart Medical Special Edition"!
In view of this, the electronic enthusiast network specifically integrates the design circuit diagram for wearable medical treatment, from the aspects of MCU, sensor, wireless module, power supply, voice alarm system, analyze the precise design of wearable!
Precision Design MCU
Design of portable heart rate monitor based on EFM32TG840
In the field of consumer electronics, portable electronic products have become more and more popular among consumers due to their small size and light weight, and have become an indispensable part of people's lives. Based on this idea, we designed a portable heart rate meter, which can replace the traditional method of measuring with pulse stethoscope and so on. It is very convenient to use. The product mainly consists of three parts: signal acquisition, data processing, and LCD display and alarm circuits.
The input signal of the voltage follower, that is, the pulse sensor signal is input from the V+ terminal, and the feedback resistor is set to zero to form an in-phase follower, which acts as a buffer to isolate the influence of the front and rear stages. The function of the heart sound pulse amplifier is to amplify the mV level heart sound signal to the V level for display and recording.
Due to the interference of external signals in practical applications, and considering the stability of the amplifier, the primary amplifier cannot achieve such a large gain, so the voltage amplifier generally consists of two stages. Among them, the front stage uses a negative feedback differential amplifier circuit to improve the common mode signal rejection ratio. The key to this part is how to suppress various noises and avoid letting noise get into the back-stage circuit. Therefore, in the system, the micro-power instrumentation amplifier LM358 based on the dual op amp circuit is used as the preamplifier of the heart sound pulse signal. In order to prevent the occurrence of nonlinear distortion so as to impair the common mode rejection ratio of the circuit, the amplification factor of the portion should not be too high, and the selection is about 1000 times.
The following sections mainly include the MCU control display circuit and the alarm for driving the buzzer. The specific circuit is shown in Figure 4.
Elecfans technical editor comment: This design realizes real-time measurement of heart rate signal through digital-analog hybrid circuit combined with single-chip control design, and can issue warning. The whole circuit takes into account various factors as much as possible, so that the line is simple, the electromagnetic field interference is reduced, the software programming is fully utilized to make up for the lack of precision of the components, and the standby time is made due to the introduction of the world's ultra-low power ARM-EFM32. The ultra-long, functional upgrade space is also very large, and other functions can be loaded based on the design, so that its function and structure are more perfect, and extended to the determination of other physiological states of the human body.
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