A surprisingly good ECG is possible from a single op-amp. This project contains circuit and software.
- Project page: http://www.swharden.com/wp/2016-08-08-diy-ecg-with-1-op-amp/
- YouTube demo of project in action: https://www.youtube.com/watch?v=AfirWls9Sys
Many people have found this python program difficult to use. A simpler program (with a click-to-run EXE you can download and run on any computer) is here:
https://github.com/swharden/SoundCardECG
This software needs certain libraries like PyQt4 and numpy, so the easiest way to make sure you have versions of everything that get along is to download a pre-packaged Python distribution. This software has been tested and works with WinPython 3.5.2.1 (not the Qt5 one)
- install WinPython-64bit-3.5.2.1 (not the Qt5 one)
- download this project and modify go.bat to reflect where your python.exe is
- build the circuit, plug it into your microphone hole, and run go.bat
