6 Replies Latest reply on Oct 10, 2019 1:06 PM by EvPa_264126

# PSoC 5 ECG signal issues

Hi everyone! I am trying to implement an ECG on PSoC 5 and I am doing this way:

With this configuration I got this signal:

However, it does not show clearly the QRS complex. I think that it could be the ADC clock. Because it allows at least 1MHz of clock frequency. I guess that if I could change the clock to 100 or 200 Hz, maybe the system would not be affected significantly by the High frequencies. So, I would like to ask you if someone has some idea of how I could resolve this problem and visualize the QRS complex.

That's it, thank you all.

• ###### 1. Re: PSoC 5 ECG signal issues

If possible, post your project here.

The ECG signal requires a differential amplifier circuit with a small positive bias.

(useful signal less than 1mV against a common-mode signal up to hundreds of millivolts)

Your signal is very similar to (50 / 60Hz)

• ###### 2. Re: PSoC 5 ECG signal issues

The first two amplifiers I tried to simulate an instrumentation amplifier. This configuration I got here: https://www.cypress.com/file/53376/download

The third amplifier I put it based on the circuit that is presented in this video(in the minute: 7:20): Électrocardiographe / Moniteur cardiaque / DIY Electrocardiograph - YouTube

I have 99% sure that the signal I got is an ECG signal because when I do not put the electrodes on my skin, it is a constant. I will post above the link to download my project:

An observation: in main.c I multiply the signal by -1 because I got it inverted after the third amplifier.

• ###### 3. Re: PSoC 5 ECG signal issues

You are using unipolar power supply for the PSoC.

Therefore, you must ensure that the input bias is at least> 0 above 100mV.

odyssey1 processed signals less than 0 (up to +/- 100mV) at  lower  reference voltage for the ADC.

But I don't remember which topic.

• ###### 4. Re: PSoC 5 ECG signal issues

A signal simulator will help you understand the range in which you measure the signal.

• ###### 5. Re: PSoC 5 ECG signal issues

I tested the signal simulator that you sent me and I got this signal:

So, I have some questions that I would like to ask you:

Tha ADC is by passed, what is its reference? Is it the E2 pin?

Where the extern variable WaveDAC8_1_wave2 is defined and declared?

Why the ECG_Wave is not used?

Do you think that my ECG circuit is correct?

• ###### 6. Re: PSoC 5 ECG signal issues

1. ADC has internal Vref and requires a bypass capacitor (pin P0 (4))  so it was in your project

2. extern variable WaveDAC8_1_wave2 is defined and declared on line 35 (replacement procedure at  lines   33-36)

3. ECG_Wave - real ECG + 50Hz noise  is not used in this project.

4. The resistor R_1 is 11 ohms  (use 50-100 ohms to start)

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The ECG signal is very small (<1mV), hidden in a huge interference signal (50/60 Hz) and may have an offset from skin-galvanic reactions (up to + - 300 mV)

Look for a description of the real ECG signal and its components, for example, this.

Therefore, you will have to use a differential amplifier with   capacitors at the input.

here are my old projects (PSoC5, russian)

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