It is a bit disappointed to see that both my high pass and low pass filters not working. But I am not too upset, because I knew I was doing a quick and dirty project, using the simplest hardware, without much serious design. I guess the main problem is that the resistor value of the RC low pass filter is too high, therefore picking up too much noise. One thing I should do is to use OP AMPs which should pick up much less noise and better performance. But I saw that the opamp circuit is a bit too complicated, so I was too lazy to try my luck that way.
But I am still happy to have revised the RC network which I learned ages ago in technical college, and had almost forgotten the details. All these years, I still found the idea of using imaginary numbers to represent the phase a bit too abstract, at least comparing to the digital logic circuits which I have always been comfortable to play with.
Anyway, so much for the preliminary test of ECG for now.
I was thinking of shifting also the scope from the desktop, to get more desktop space to switch in my other suspended project, the NXP LPC1114 barebone thing, ...
But, wait a moment, I heard someone knocking at my door, ...
.END
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