I am trying for the beginning to run a simple Arduino code in order to test the functionality of the ECG sensor. What I am getting on the output are some random values around 600 or around 200. I connected everything the same as in any tutorial about AD8232: GND -> GND, 3.3V -> 3.3V, L0+ -> digital pin 10, L0- -> digital pin 11, output -> analog pin A0. I placed the sensor pads on my body like in pictures (forming a triangle), but regardless of putting the electrodes or not, I always get the same floating signal. Here is Arduino code:

int ecg;

void setup() {
  // put your setup code here, to run once:


void loop() {
  if((digitalRead(10) == 1)||(digitalRead(11) == 1)){
    // send the value of analog input 0:
    //Wait for a bit to keep serial data from saturating

When I run this code I get only "!" on the output, no matter where I put the electrodes on my body. When I comment "if" and "else" parts of the code and print directly only reading from the pin A0, I get those random floating values, like on the image. Random values from analog pin A0

I also tried another custom built ECG sensor, but the results are the same. I haven't found the solution anywhere. It is not about the noise, because when I touch the metal box of my PC, I only reduce the values but there is still nothing on the output.

  • I only reduce the values but there is still nothing on the output. Have you tried measuring using a laptop that isn't connected to AC? Not to mention, have you added large electrolytic capacitors to the 3.3V bus and made sure it can supply enough current for the sensor?
    – Avamander
    Commented Aug 31, 2019 at 10:26
  • It is OK to accept your own answer as a solution to the problem. I think you get 15 rep for it.
    – VE7JRO
    Commented Oct 21, 2019 at 14:51

1 Answer 1


The problem was that I connected GND on the other half of the protoboard and there was no connection. I thought that the whole length of the protoboard is on the same potential for + and -, so GND wasn't connected. After connecting GND pin correctly, all worked perfectly.

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