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Yes I'm using the 7805 to get -5V relative to circuit ground, to form a dual power supply. The circuit is designed to work with 5V, 0V (GND) and -5V mainly because of the instrumentation amplifier.
Yes using an electrode might improve the signal because anti-static strip has a fair amount of impedance. It was just a quick and cheap way to make a grounding electrode.
Dude everything is up here, if you have more specific questions I'll answer them.
Yes, sure because the frequency content of the signal is very low so with a normal sound card sampling at say 44kHz you'll easily get a perfect sampling. There is plenty of info on the internet on how to use a pc or cellphone as an oscilloscope.
The oscilloscope is a DSO-nano V2 made by seeedstudio, the LCD is a standard 16x2 character LCD
WOW! It looks awesome! :) Is that gorgeous TFT screen only used for displaying the heart rate? Because you could try to modify my design to sample the ECG signal with the arduino and display it live on the screen! Anyway, I'm interested with the mods you've brought, can you send me a private message? I would love to add your build to my project as an update or something like that, with your permission and attribution of course!
As SophieR23 says (special thanks to her) the heart rate signal is really small, in the order of 1mV peak-to-peak. The main problem is the noise coming in the circuit through the body, typically in the order of 100mV peak-to-peak or even more, so if you use a standard amplifier, you'll only get noise at the output. The instrumentation amplifier is a badass amplifier who does an amazing job at removing common-mode noise (i.e when the same noise is present on both electrodes), so it amplifies the differential ECG signal while decreasing the noise.
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