HOWTO make a cheap ECG with an old PC sound-card

Here's a HOWTO for building your own electrocardiograph -- many such plans exist, but this one lowers the cost and part-count by ingeniously repurposing the sound-card from a PC.

Digitization: Once amplified, the ECG signal along with a bunch of noise is in analog form. You could display the output with an oscilloscope, but to load it into your PC you need an analog-to-digital converter. Don't worry! If you've got a sound card with a microphone input, you've already got one! It's just that easy. We'll simply wire the output of our ECG circuit to the input of our sound card, record the output of the op-amp using standard sound recording software, remove the noise from the ECG digitally, and output gorgeous ECG traces ready for visualization and analysis!

DIY ECG Machine On The Cheap (via Make)


  1. Doesn’t seem to be very useful. You can basically measure your heart rate, which you could measure more easily with other means. There’s a lot of information in the other features of an ECG like the P and T waves which could tell you about certain heart defects.

  2. This would be a PERFECT use for an OLPC in third-world countries. Simple sensors leveraging the CPU and display of the OLPC to provide adequate medical info to diagnose ailments that couldn’t otherwise be discovered…

    Just imagine, a $200 OLPC acting as a machine that goes “Ping!”

    Of course, my optimisim is based on my near-complete ignorance of the diagnostic value of the results the above ECG could provide…

  3. @Timothy Hutton: I have no idea whether or not such a setup would be of any realistic use(most notably, I’m not sure if there are any conditions an ECG would diagnose that cost less than an ECG to cure); but the OLPC’s audio input system was, I’m told, designed with potential signal visualization use in mind.

  4. Personally, I would like to know if there is a DIY EEG for looking at the brain waves.
    That just seems more fun to me.

  5. So for the last 20+ years, nobody noticed that a sound card has an A/D converter on it?

    A long time ago I had a job programming an A/D converter for an EEG lab. Apart from a few features, such as 64 channels, it didn’t seem that different from a sound card. One difference is that we jumpered a precision timer trigger from another board so that we had good time resolution.

    Two channels isn’t much of an EEG though.

  6. One channel, surely? Two leads = enough to detect one signal between them.

    Although I guess you could get two out of it if your soundcard has stereo input.

    And yeah, as someone who has had cardiac arrythmias, for an ECG I’d only really be interested in the full 12-trode version. An Arduino would probably be a better way of doing that (with a bunch of tiny op-amps, I guess).

  7. The audio input of the OLPC laptop does work as a voltage and signal sensor, and there’s a “toy” voltmeter and oscilloscope program included in the packaged software.

  8. This is a seriously bad idea.

    Proper ECG equipment uses an isolated front end to prevent leakage of 60Hz line current through the body of the person being monitored. Quite small amounts of 60Hz current can cause fibrillation of the heart and death.

    The one safe alternative would be a completely battery powered system with nothing connected to an electrical outlet.

    From a circuit design perspective it is preferable to use an instrumentation amplifier rather than an Op-Amp.

  9. This is new? I remember reading ECG designs using your computer’s sound card for awhile now. As well as oscilloscope designs.

    Note these are meant for fun projects not realistic use. The audio in from your computer gets alot of interference compared to professional ECG machines. With one/two channel design like this, you’d the same usefulness as taking the pulse with your two fingers. Granted the visual effect of spotting erratic beats would be much faster then using your fingers. But you would know by looking at the patient.

    As for oscilloscope, I find it handy and low cost. Still nothing beats a $1k flat screen machine compared to your limited wires coming out of your soundcard.

  10. What if suddenly, I start to Derez and become part of the computer? Too frightening to think about.. no thanks !

  11. Mitch Rohde designed and built an ECG module for the game boy system. The idea was to produce low cost medical equipment for the third world. Patent number 5876351, but I’m not sure if it’s going to make it to market.

    -Jeff Bell

  12. Proper ECG equipment uses an isolated front end to prevent leakage of 60Hz line current through the body of the person being monitored. Quite small amounts of 60Hz current can cause fibrillation of the heart and death.

    Also, be sure to wear safety goggles and a respirator when working with sand.

  13. From a safety aspect, how different is this from plugging a pair of headphones into your PC and pressing them against your head?

  14. #13 Yes, a laptop on battery would be fine.

    #14 The idea of modifying a Gameboy is excellent. I first considered this kind of thing back in the days of the MicroVision. I was doing design work for a medical electronics firm and the idea of a cheap handheld ECG was a lot more novel.

    Our dear friends at the FDA make sure medical equipment is safe but also very much more expensive. The idea never went anywhere.

    #17 The person being monitored is unavoidably part of the circuit. When you put headphones on you are not in the circuit. Visualize an ECG with two leads fastened to the patient with current flowing in a loop through it as opposed to the plastic earcups of the headphones on your head. If you touch the ground connection of the headphone jack it likely has no potential on it. If it does you are only in trouble if you are touching something else that will close the current loop.

    #15 People sometimes get killed doing stupid things. Go ahead and see what happens. You probably will survive. But you might not.

  15. There was an EKG program developed in Google Summer of Code using an OLPC XO laptop to display the trace. The XO’s Sugar software includes the Measure digital oscilloscope function, which reads the sound port.

    Naturally, you would not use such a device in a properly-equipped clinic. I suggested the design on an OLPC mailing list as part of a telemedicine system where villagers could be tested by village health workers with quite modest training. The data would stream live to a clinic or doctor’s office over wireless, and the doctor could tell the patient whether to come in for more diagnosis or for treatment.

    We know how to build such systems for vital signs, imaging of eye, ear, nose, throat, and skin, and audio (digital stethoscope). At some point the non-invasive blood chemistry measurement products now being developed for diabetics (no finger sticks) will be extended to a wide range of blood tests, and will come down considerably in cost. We can consider adding these functions to village telemedicine when we get sufficient bang for the available buck.

    Of course, the OLPC plan is to end poverty through education, providing lots more bucks for health care and other needs over the next generation. We shall see.

  16. hello
    I like the idea of DIY EEG.The 24hour monitor I had once had 6 or so electrodes.

    I have heart palpitations and the hospital doesnt have enough 24hour data logging devices.

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