How to Make an ECG

The origin of the electrocardiogram (ECG) has its roots in the diagnosis of various forms of heart disease, including arrhythmias (problems with rate and rhythm) and acute myocardial infarction. Dutch physiologist Willem Einthoven invented the electrocardiogram in 1902 to provide physicians with an avenue for these diagnoses. Here's how to make your very own!

You will need the following:

- LTSpice

- Breadboard circuit

- Wires, Capacitors, Resistors

- Arduino board

- Electrodes, oscilloscope, wavefunction generator, power source (9 V battery or power generator)

The first step of the ECG creation process is simulating the circuit on LTSpice in order to see if it functions properly! The circuit will be broken up into three sections: the INA component, the notch filter, and the low-pass filter. When making your own simulation, you can use the same setup and values as seen in the picture or you can change them up on your own! As long as the INA has a gain of 1000-2500, the notch filter has a cutoff frequency of 60 Hz, and the low-pass filter has a cutoff frequency of 330 Hz then you are good to go.

Construct an amplifier as seen in provided picture, with a gain between 1000-2500 dB (use R values in kOhm range).

Using the function generator, input a sinusoidal wave into Vin2 with an amplitude of 10 mV, a frequency of 100 Hz, and no offset (send the input signal to the oscilloscope as well). Connect Vin1 to ground and V0 to the oscilloscope. Verify the correct gain is being read on the oscilloscope In order to create a magnitude versus frequency plot, increment the frequency of the function generator and record observed output values.

Construct a notch filter as seen in the provided picture, with a cutoff frequency of 60 Hz (use R values in kOhm range).

Using the function generator, input a sinusoidal wave into V1 with an amplitude of 10 mV, a frequency of 10 Hz, and no offset (send the input signal to the oscilloscope as well). Increment the frequency towards 60 Hz, making sure to move in smaller intervals when nearing the target frequency Check to make sure that the maximum amount of attenuation occurs around 60 Hz. After confirming that your notch filter is functioning properly, increment the frequencies of the function generator and record corresponding the outputs to create a magnitude versus frequency plot.

Construct a low-pass filter as seen in the picture provided, with a cutoff frequency of 300 Hz (use R values in kOhm range).

Using the function generator, input a sinusoidal wave into V1 with an amplitude of 10 mV, a frequency of 100 Hz, and no offset (send the input signal to the oscilloscope as well). Increment the frequency towards 300 Hz, making sure to move in smaller intervals when nearing the target frequency. Check to make sure that the maximum amount of attenuation occurs around 300 Hz. After confirming that your low-pass filter is functioning properly, increment the frequencies of the function generator and record corresponding the outputs to create a magnitude versus frequency plot.

Connect the individual components created in previous sections in their respective order, with the output of the INA going into the input of the notch Filter, and the output of the notch filter going into the input of the low-pass filter.

Connect ECG electrodes to a volunteer in the formation seen below in provided picture with the positive electrode connecting to Vin2 of the INA and the negative electrode connecting to Vin1 of the INA.

Have the output of the complete circuit connect to an oscilloscope and ensure the volunteer remains still for accurate results. Record your results as displayed on the oscilloscope. Clear P, QRS, and T waves should be visible on the device.

If you have clear results, wire up your circuit to the Arduino with the provided code and view your very own heartbeat with a provided bpm tracker!!!