The personal website of Scott W Harden
Source code for Homemade ECG Machine: Improving Daily
---
title: Homemade ECG Machine: Improving Daily
date: 2009-02-02 16:50:36
tags:
  - diyECG
---

# Homemade ECG Machine: Improving Daily


> **⚠️ Check out my newer ECG designs:** 
* [**Sound Card ECG with AD8232**](https://swharden.com/blog/2019-03-15-sound-card-ecg-with-ad8232/)
* [**Single op-amp ECG**](https://swharden.com/blog/2016-08-08-diy-ecg-with-1-op-amp/)


__I've been working on a homemade ECG machine over the last month.__ [This is the most basic circuit](http://www.swharden.com/blog/images/diy_ecg_circuit.png) I'm currently using, designed using two quad op-amps. I've produced some [surprisingly good ECG traces](http://www.swharden.com/blog/images/nicetwopng.png) and even [identified an arrhythmic heartbeat](http://www.swharden.com/blog/images/murm2.png). Currently the device is limited because you have to be attached to your computer, I'm working toward making it a mobile device (powered by a 9V battery) which records voltage data to a [minidisc recorder](http://www.minidisc.org/images/sony_mznh900_silver_mymd.jpg) . There's one problem - I need to optimally adjust the gain, but how if I cannot see the trace of the wave on a monitor? I could a VU meter to monitor the output... My minidisc recorder can take mic-in and echo it the line-out at the same time, so I'll just put the VU meter on the line-out and it shouldn't affect my trace. The result is that I can walk around for 24 hours, recording my ECG, with a device I hope to get down to the size of a cell phone. (Maybe a 1990s cell phone?)

<div class='center border'>

![](vu_meter.jpg)

![](vu_meter2.jpg)

</div>

__Here's a simple LED-based digital VU meter circuit__ I found, along with some sample images of its (bread-boarded) construction. I have all the parts at home I think, so it should be straightforward to make. The pain now is the electrodes (which are still the junky ones made from scissor-cut aluminum cans), and I think I might splurge and buy some actual disposable ECG electrodes. I think the total cost of my device as it stands is about $4, so I don't want to spend more than I have to on electrodes.

<div class='center'>

![](vu_circuit.png)

</div>

__In other news__ it appears I've been accepted into dental school. I got a voicemail this morning at 8am, another one at 12:30pm, and apparently one on my parents' answering machine (I listed them as an alternate number), then they sent me an email! Naturally it was the email I noticed first. Here's a snapshot from my inbox, [phone call 1](1.mp3) and [phone call 2](2.mp3).

<div class='center border'>

![](accepted.png)

</div>
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