UPDATE: An improved ECG design was posted in August, 2016.
Check out: http://www.swharden.com/wp/2016-08-08-diy-ecg-with-1-op-amp/
So I followed-through on yesterday’s post and actually tried to build an ECG machine. I had a very small amount of time to work on it, so instead of building the fancy circuit (with 6 band-pass filtered op-amps and diodes posted in the previous entry) I built the most crude circuit that would theoretically work. I used one of the 4 available op-amps from a LM324 chip (pictured to the left) . I was working late at night, and I’m quite colorblind, so I had to take a gamble (as usual) with the resistors I used. Resistors are color coded with bands that represent their resistance. But, since I’m highly colorblind, red, orange, and black all look the same to me. So I can’t be sure I go the resistances right. I’d check it with my digital multimeter but I seem to have lost it and my wife doesn’t remember seeing it recently. Blast! Anyway, I built the sucker, hooked it up to my sound card, and made electrodes by soldering wires to pennies. After a good lick, I attached the pennies to my chest with tape and tried recording. Every time the pennies made contact with my skin, I would see noise on the trace, but I couldn’t seem to isolate a strong heartbeat signal. This is what I saw and the circuit I build to see it:
When I have more time I’ll locate my multimeter and build the full circuit described below. I’ll update everyone on my progress later. Wish me luck!
Perhaps this project will be working soon. How cool is that? Many techno-savvy people have made these DIY ECG machines, but no where on the net do these people describe how to interpret the data. Since I’m planning on building it, testing it, recording ECG data, and processing/analyzing it, I’ll have something truly unique on the internet. Perhaps it will be worthy of mention on Hack-a-day when it’s complete! How cool would that be?