ECG Project- Extra Credit BME 305 Final Design Project

The goal of this project was to create a functional ECG using an instrumentation amplifier, notch filter, and low pass filter.

The table below shows the supplies that were used to create this project. The exact capacitor and resistor values are shown in the next section with our theoretical circuit diagrams and outputs.

The first step to creating a functional ECG is to design circuit diagrams and test them to ensure that the device you're creating will function properly. The circuit diagrams for the low pass, instrumentation amplifier, and notch filter are shown in the next 3 steps. The resistor values are also shown in these diagrams.

The low pass filter had a cutoff frequency of 150 Hz to remove unwanted noise from the ECG output.

The instrumentation amplifier had a gain of roughly 1000 because the signal inputted from an ECG is usually 1.0-2.5 mV and in order for the signal to be easily viewed on the oscilloscope, it should have a voltage of 1-2.5 V. The output is the difference between the G1_lead and G2_lead times the gain. LM741 op amps were used. In the theoretical diagram, there is a source power of 15 V, but when doing this with an actual person, ensure the op amp source power is 9 V batteries to ensure it is safe for the person.

The Notch filter had a center frequency of 60 Hz to remove noise from the AC wall power which operates at about 60 Hz.

The overall circuit diagram is shown above as an example. However, as long as you follow the theoretical circuits from the previous step and create these circuits, it should function properly. Any size breadboard is able to be used. We utilized a smaller breadboard to make our circuit more compact and in order to practice effective utilization of space.

We also utilized an arduino Uno in order to be able to visualize the ECG and BPM in real time. The code is shown here and the outputs we were able to receive are also displayed. We found this to be able to be relatively consistent with manually obtained BPM. Ensure the subject is sitting completely still when doing this portion of the project.

I hope you are able to benefit and learn from this project! It was certainly very interesting and engaging for the team that designed this. It is always really cool to see theoretical knowledge you learned about online or in school apply practically in the real-world! To further improve your ECG, you can implement an active low pass filter in place of the passive low pass filter we used. You could also add a high pass filter to eliminate more noise from the signal. Happy learning!