Make your own Realtime, Lowcost and Portable ECG Device

Realtime ECG Waveforms 

Video 1. The output of Lowcost, Portable ECG Device

    ECG waveform in the above video was acquired by the device that my friends and i made. The portable ECG acquisition device includes Electrodes, Some circuits, and Arduino. By these three components, I have made Realtime, Low-cost & Portable ECG acquisition device. To make this type of device lets go through the following steps. 

    The price of the overall device is below INR 2000. It is operated by 9V batteries so the portability of the device is increased.

What is ECG and Application of the ECG machine?

    Human cells present in the human body generate electrical potential which transmits throughout the body by the cell itself. SA node present at the right atrium in the human heart generates ionic potential and transmits it throughout the heart and that potential transmission generates ECG waves, as well as heart contraction and relaxation. ECG machine identifies the electrical activities/potential of the human heart. 

    As per the Einthoven triangle theory for ECG, the Right Leg is not in a position of the action potential transmitting vector of the human heart. That's why it is always grounded.

Figure 1. ECG waveform

    The application of the ECG machine is to diagnose the cardiac activity of the human heart. The irregular ECG waveform shows cardiac disorders such as arrhythmias, bradycardia, tachycardia, early symptoms of heart attack, etc. If the diagnosis of ECG waves detected as early as possible then treatment can be given to the patient at the right movement.

You should have a good understanding of below topics to make portable ECG Device:-

• Circuiting
• Arduino (Optional)
• Electrodes for ECG acquisition 

Block Diagram

Figure 2. Block Diagram of ECG Circuit

• As you can see in the block diagram the circuit part contains the Instrumentation amplifier and filter section. The amplitude of the ECG signal is very low(Approx. 5mV) and it contains an interference signal. To amplify low-level signals we have to use the Instrumentation amplifier. That's why I have used the instrumentation amplifier.
• The frequency of the ECG wave lies between 0.5 Hz to 150 Hz so it is required to attenuate further frequency. To remove greater than 150 Hz frequency I have used Low pass filter only. I have used the 4th order Low Pass Filter to attenuate greater than 150Hz frequency. I didn't use a high pass filter to attenuate below 0.5 Hz frequency because its value tends to zero that's why we can negotiate it. 
• If you are using external power supply then you have to connect the Notch filter to remove 50 or 60 Hz noise coming from AC Powerline because it will affect the signal. I am using two 9V batteries to supply voltage so, I didn't use the notch filter.
• The software part contains Arduino on your PC. Connect the Arduino board with your PC.

Software Requirements:-

• Any PCB Design Software (Optional)
• Arduino IDE

Component Requirements:-

• ECG Disposable Electrodes (Quantity: 3)
• ECG Electrode cables (Quantity: 3) 
• General Purpose Board (Quantity: 1)
• AD620 Instrumentation IC (Quantity: 1)
• TL084 Operational Amplifier IC (Quantity: 1)
• 0.22uF Electrolyte Capacitor (Quantity: 4)
• 47 Ohm Resistance (Quantity: 1)
• 4.7 kOhm Resistance (Quantity: 4)
• PBT 2 pin Connectors (Quantity: 6)
• 8 pin IC Socket (Quantity: 1)
• 14 pin IC Socket (Quantity: 1)
• 9V Battery (Quantity: 2)
• Male-Male Jumper wires (Quantity as per requirement)
• Male-Female Jumper wires (Quantity as per requirement)
• Female-Female Jumper wires (Quantity as per requirement)
• Arduino (You can use any Arduino board)

***Read the whole page before buying components***

Let's make it 

Always remember below points when you are making ECG device:-

• Choose disposable electrodes in place of other electrodes because disposable electrodes have electrolyte jelly at contact surface which is a good medium for electric conductivity. Once the disposable electrode will stick at the surface of human skin then it will not move from that place which helps negotiates the unwanted movement of electrodes.
• Take three-electrode wires compatible with disposable electrodes available in the market.
• Here, I have used AD620 as an instrumentation amplifier because it is perfectly compatible for ECG acquisition as mentioned in its Datasheet. The main advantage of AD620 is that I have to use just one resistance to vary the gain.
• Always use the IC sockets if you are using IC because it will help you to replace IC easily if it will blow.

Instrumentation Amplifier Circuit

• I used here 47 Ohm resistance because the gain that I require is 1000 (Approx.) because the amplitude of ECG waves is 0-5mA so we can gain it up to 1000 so we can get those signals in 0-5V range.

(0-5 mV) * 1000 = (0-5) V

• As per equation show in Datasheet of AD620

G = 1 + (49.4 kΩ/RG)  

• if you put G = 1000 so you will get the value of RG is nearer to 47 Ohm which will give you gain of 1000(approx.). 

Figure 3. Instrumentation Amplifier

Figure 4. Instrumentation Amplifier (Circuit Board)

Filter Circuit

(150 Hz Low pass 4th order filter)

Figure 5. 4th Order Low pass filter

Figure 6. 4th Order Lowpass filter circuit

Arduino

Figure 7. Arduino

• Attach Arduino cable to your PC. 
• The output of the filter circuit connect it to any analog pin available in Arduino(I have highlighted it with red color in figure 6) I have connected it to Analog 0 pin and run the below code.

Figure 8. Arduino File Selection

• Now upload program and Open Serial Plotter in Arduino as shown below.

Figure 9. Selection of Serial Plotter in Arduino

• After Uploading code and open a Serial Plotter so that you can see now ECG Signal as shown below on your screen.

You can contact me on krunalprajapati778@gmail.com for help. I will help you whatever I can.

Thank You 

Made By:

Krunal Prajapati 

Vijayrajsingh Solanki

Shah Priya

Guided By:

Prof U.V. Pancholi, LD College of Engineering

This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.