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