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DIY ECG with 1 op-amp

Posted on Monday, August 8th, 2016 in DIY by DP

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A DIY ECG made from single op-amp (LM741) and 5 resistors by Scott Harden:

I made surprisingly good ECG from a single op-amp and 5 resistors! An ECG (electrocardiograph, sometimes called EKG) is a graph of the electrical potential your heart produces as it beats. Seven years ago I posted DIY ECG Machine on the Cheap which showed a discernible ECG I obtained using an op-amp, two resistors, and a capacitor outputting to a PC sound card’s microphone input. It didn’t work well, but the fact that it worked at all was impressive! It has been one of the most popular posts of my website ever since, and I get 1-2 emails a month from people trying to recreate these results (some of them are during the last week of a college design course and sound pretty desperate). Sometimes people get good results with that old circuit, but more often than not the output isn’t what people expected. I decided to revisit this project (with more patience and experience under my belt) and see if I could improve it. My goal was not to create the highest quality ECG machine I could, but rather to create the simplest one I could with emphasis on predictable and reproducible results. The finished project is a blend of improved hardware and custom open-source software, and an impressively good ECG considering the circuit is so simple and runs on a breadboard! Furthermore, the schematics and custom software are all open-sourced on my github!

Project info at Scott Harden’s blog.

This entry was posted on Monday, August 8th, 2016 at 3:31 pm and is filed under DIY. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

2 Responses to “DIY ECG with 1 op-amp”

  1. Tweeks says:

    Here.. you forgot the crystals…

    :)

  2. RoGeorge says:

    The author wrote as a warning, in red, to use a battery, and NOT a power supply. This precaution is useless because the GND is connected by the Jack cable to the computer GND.

    The computer GND does NOT have a galvanic isolation, so if you are unlucky enough, THIS SETUP MIGHT KILL YOU !!! No kidding here, it might literally kill you.

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