AD8232 output problem

Discussion created by cuddrow on Feb 12, 2018
Latest reply on Mar 2, 2018 by

I teach physiology, and in order to show my students how one can build a simple system for doing at-home ECG and heart rate measurements, I bought and assembled an AD8232 to use with my Arduino UNO. I have used the guide at AD8232 Heart Rate Monitor Hookup Guide - although without using an Arduino Mini Pro. This means that I have also omitted the breakout board required to interface the Arduino mini with my computer. I have attached an image of my serial monitor output and of the output from the Processing code provided in the link above. I am using the same Processing version that they recommend (v2.2.1) and I have tested this both on my portable mac (both with and without the power supply) and on my stationary PC. The problem, as you can see, is that the signal bounces somewhat randomly between 0 and ~675 if I connect all three electrodes anywhere on my body. Sometimes it settles into a pattern of "poles" (see attached image) at roughly 2Hz, but it tends to be erratic. I have tried all sorts of configurations with no luck. The board is powered with the USB from the computer, the same one used to do the serial monitoring. I have noticed that the value appears to hit 675 if I touch the aluminum cabinet of my laptop and bounce back down to 0 when I stop touching, leading me to think there might be some capacitative effect in action. This effect is not entirely stable, but a clear trend appears to be present. I also tried putting a potmeter on the 3.3V but this simply displaces the effect described above. I honestly don't know what else to test, and I was hoping you guys had some suggestions.