Heart rate monitoring using MAX30101
The heart rate is a measure of the number of heartbeats per minute, which is usually expressed as "a number of times per minute" or BPM. The photoelectric capacity is used as a very common way to measure heart rate. There are two forms in the photoelectric capacitance method, namely, reflected photocatalysts, and transmitted photocandonizers. In the transmitted photocatalytic mode, the light is irradiated through the end of the finger and the detector, and the amount of light is measured. When the heart is pumped through the body, we noticed that the blood volume of your fingers increased. That is, the amount of light through the finger changes with the change of blood, and then detects the photodetector. In the transmissive photoelectric volume, we measure the amount of light reflected from the finger, rather than measuring the amount of light through the finger. The MAX30101 of Maxim Integrated uses a dedicated integrated circuit to perform reflected photoresistance records. The MAX30101 contains three light emitting diodes, a red, an infrared and a green. The IC also includes a photodetector that includes all signal processing circuits to detect heartbeat and then calculate the heart rate. By using this dedicated IC, we can detect heartbeats and calculate the heart rate.
Many users have developed a library for the MAX3010x series chip. I use the MAX30101 because there is green light function. The MAX30101 cannot work properly before the end date of the game. However, the MAX30100 used before I can work. The MAX30100 and MAX30101 are basically the same. I use the MAX30100 to collect data. As shown below, the first large peak you see is my heart suction (ventricular contraction), the reason why the blood volume suddenly increases. The second peak indicates that the aortic valve in my heart is closed.
Pulse oximeter with MAX30101
The pulse oximeter is an instrument for measuring oxygen solubility or blood oxygen saturation in the blood. In order to do this, we will calculate the heart rate using photoelectric volume. Compared with the simplicity calculation, the pulse oxygen saturation is higher, requiring considerable amount of treatment and clinical verification to obtain reasonable indicators. However, we can get valuation by some DIY skills. At present, I added a pulse oxide measurement on my board.
Electrocardiogram, electrocardiogram and electric eye map for EXG circuitry
Biological potential measurement is a bioelectric signal that can be measured when we achieve certain functions. Such as electrocardiographs and electromovics are very popular. Each result in these measurements can be done using a very simple circuit. Of course, some more complex circuits can measure more data. Supperm monitor, I will use a simple meter amplifier circuit. The meter amplifier is an interface to the body electrical signal, similar to the measurement voltage of the multimeter. The multimeter has a very high impedance, so the circuit we are measured will not be overloaded. Our instrumentation amplifier is similar to the principle of measuring the biological potential signal.
The following numbers are some signals captured using Arduino 101. The first figure is an electrocardiogram that records the electrical signal of the surgical process center. The second is an electromoelectric, which measured electrical signals that cause muscle contraction. The third is an electrical map, which measures the electrical signal generated when the eye is left.
Measurement of biological impedance using AD5934
Biological impedance is another type of bioelectric measurement method. However, for biological impedance, we measure the body's impedance rather than measuring electrical signals generated by the body. Biological impedance analysis can be used to calculate body fat or analyze sympathetic neurons. I am also modifying some errors in the biological impedance circuit in the signs of the signs. At the same time, I will use some reports written by students to analyze some of the physical indicators expressed by biological impedance.
However, the biological impedance circuit is first described. This circuit uses AD5934 to impedance analysis, which is a very delicate chip for measuring the impedance of different targets. In my example, we want to measure the impedance of the biological system. In my circuit, the AD5934 output labeled "VOUT" is first passed through high pass filtering, and is centered on 1.65V (half of the supply voltage), and then fed into buffer amplifier (OTAA). OTAB is a current converter. RTUS is an organization that is studying, or any biological material. You can connect to RTUS through the installed needle. The subsequent updates may be changed to TRRS jack. It seems to be more beautiful. For example, RTUS can be connected to the arm to calculate the fat / moisture in the arm.
Biological impedance circuitry is very careful. In this circuit, you should inject a small current to your body. However, the 1 mAh current causes a stabble. Biological impedance circuit design does not exceed 100 microamines.
Measure body temperature using MLX90614
The body temperature is an important indicator for measuring health. We often use body temperature to diagnose fever and other diseases. MLX90614 is a portable method of measuring body temperature because it is non-contact. In order to obtain an appropriate body temperature, we do not need to fix the temperature sensor in the body, but the temperature of the rectal is required. Arduino will communicate with MLX90614 using I2C. ADAFRUIT has written a very good library for MLX90614. We use the examples in the Routine folder to communicate read data. When I take the hand near the sensor, I can see the temperature increase from 69 degrees to 90 degrees. When I removed from the sensor, the temperature fell to approximately 71 degrees.
Environmental light and CDS light battery
Sunlight is very important for health. It may not be as important as other indicators, but according to some studies, there is no sunshine that has no sunshine in a long time. In addition, too much sunshine also has a negative impact, causing sunburn. In order to characterize the ambient light, I added a photovoltaic cell on the instrument. The photovoltaic battery is a very simple component that can change the impedance by changing the light. We connect the photoelectric tube to the divider and read the voltage change to observe the changes in the ambient light. It is undeniable that in order to realize the sun intensity to prevent sunburn, it will make more meaningful. UV is the main reason for sunburn. A UV sensor will be added in later updates.
Using thermistor measurement ambient temperature
Using a ambient temperature sensor for temperature measurement. For some people, the sudden changes in the weather may cause colds, arthritis episodes. No one likes to be cold, so I can use this sensor to assess comfort. Thermistors are ideal for ambient temperature sensing because they are cheap and can be easily connected to the microcontroller. For our temperature sensing circuit, we add thermistor in the voltage divider circuit. The temperature can be easily calculated as shown above.
The sensor is tested by measuring the ambient temperature of the living room, whether or not, the thermistor is touched by a finger. My thermostat is set to approximately 18 degrees Celsius (65 degrees, but the living room will rise a few degrees. The sensor reading is about 24.4 degrees Celsius, which looks a bit high. It may have a deviation of 2 degrees or 3 degrees, which is normal for such sensors. Higher accuracy can be achieved by calibrating the sensor or subtracting the offset. When touching or with a finger friction sensor produces a little friction, the temperature is slightly elevated.
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