WEEK 2

Part 1 - Pedometer

The whole algorithm was shown below.

Part 2 - Heart Rate Sensor

1.Use simple band-pass filter (1-3Hz) to reduce the affect of the noise.
f1=1/(2*pi*R1*C1)=1Hz
f2=1/(2*pi*R2*C2)=3Hz
where C1=1uF
R1=560K
C2=5.3uF
R2=10K
The band-pass filter with a pass-band from 1 Hz to 3 Hz to allow the heart beat signal to come through and the rest of the signal noise to be rejected.

2. Use amplifier to amplify the signal we expected.
Gain = 1 + (R2/R1)
Gate= 1+1M/10K=101

The oscilloscope was used to measure the voltage drop on the photoresistor. As expect, the voltage will change because the red light through the figure will change with the oxygen content of blood. The expected result is a pulse wave similar to human heartbeat, but the amplitude was about 3mV measured by multimeter. However, the noise was larger that the pulse although a filter was connected. The noise covered the signal we expect.

We have to use the band pass filter and solder the connection to reduce the noise, but it did not work. We built the amplifier circuit but have not get the result because of time limitation. We thought it might useless either because the amplifier might also amplify the noise

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WEEK3

2. Heart Rate Detector (1). Use the simple filter, the result can be observed, but with many noises . (2) So, we build the second order filter combinated with low pass filter and high pass filter. LOW-PASS FILTER HIGH-PASS FILTER Demonstration

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WEEK4

Heart rate detection Hardware This week, we continued the test of the second-order filter and started to compile the code. The filter that worked successfully last week failed again. We carefully checked every possible cause but still found no problems. The method was to connect the signal generator to the input of the filter and the oscilloscope to the output of the filter. A sine wave signal of a certain frequency was input and it needed to check if this signal can pass through the circuit normally. We checked the circuit and the connection was good. Next, the components were checked one by one and no problems was found. Some of the components were also replaced. However, the situation didn’t improve much. In addition to the retest of filter, the compilation of the code has also begun. We plan to display the value of heart rate on the screen of the Arduino. Only in this way can the smart watch play a practical role. Then, we simulated the filter. The result verified th...