By: Karima Khandaker, Israa Al-Qassas, Reemaz Hetaimish, Haneen Mohammed, Danah Nour, Lina Babsail, Sarah Al- Harthey Course: Introduction to Electronic (Integrated Circuits) - ECE210L Supervisor: Dr. Nema Salem Department: Electrical and Computer Engineering

HARDWARE DESIGN AND IMPLEMENTAT ION OF AN ELECTROCARDIOGRAM SYSTEM

•  What is an ECG system ? According to the Encyclopaedia of the 20th Century Technology, "the

electrocardiogram (ECG or EKG) is a graphic measurement of the electrical activity of the heart produced by an electrocardiograph, or ECG machine." The ECG is used to monitor the electrical activity of the heart which is extracted from the human body in the form of analog signals.

•  Why to build an ECG system ? to represent efficient design and implementation of a complete ECG

system starting from the signal acquisition from the human body till displaying both of the ECG signals and the rate of heart beats as well.

•  What does the ECG do ?

The Electrocardiogram (ECG or EKG) is used to measure the electrical activity of the heart over a certain period of time depending on the purpose of taking the reading. It can be used to either monitor over longer periods of time or diagnostic purposes to analyze the status of the heart at a certain time.

ELECTROCARDIOGRAM “ECG”

Fig. 1.0 Standard Setup of ECG System Used for Monitoring

•  With each heartbeat, an electrical signal is generated in a group of cells in the upper right chamber or right atrium of the heart. This signal passes through the two upper chambers (right and left atria) causing them to contract which in turn causes the blood to move in the lower chambers of the heart called ventricles. This electrical signal passing through the atria is shown as the P Wave on the ECG. As the signal passes from the atria to the ventricles it slows down to allow the ventricles to fill up with blood and this is shown as the flat region between the P and Q waves. The signal then distributes across the ventricles instigating them to contract and pump blood to the various parts of the body. This section causes the QRS waves on the ECG. Once the ventricles return to their normal state after this, it can be seen on the ECG as the T wave in Fig 2.0. The ECG allows the medical staff to deduce different conditions based on the deflection from the general expected ECG waveform. It may be based on the amplitude, shape, interval lengths or even the absence of expected waves. Table 2.0 shows some examples of comparisons between normal (expected) data and abnormal data and the conclusions that can be drawn in each case.

•  3 lead wire ECG System have three colored wires that connect to three electrodes forming the Einthoven’s triangle as shown in Fig. 3.0. This system provides three views of the heart.

HEART BEATS : PQRST WAVE ON THE ECG

Fig. 2.0 PQRST Wave

Fig. 3.0 Position Of 3 Leads Forming Einthoven’s Triangle

HARDWAR IMPLEMENTATION

Signal Extraction

Amplification System

Noise Filter System

Peak Detector System

Displays and Outputs

The overall system of the ECG can be divided into the shown 5 subsystems: Signal Extraction

•  Electrodes •  Patient Protection •  Multiplexer

Further Amplification Noise Filter

•  Amplification •  Instrumentation Amplifier

Peak Detector

•  To calculate heart rate

Output and Displays •  From Peak Detector Circuit - Seven Segment Displays •  ECG display – Oscilloscope

Fig. 2.0 Overall ECG System Block Diagram

Signal Extraction

Amplification System

Noise Filter System

Peak Detector System

Displays and Outputs

Signals are extracted from lead wire and connected to

the multiplexer that is used to select the lead to be

processed is a Dual 4-Line To 1-Line Data Selector/

Multiplexer.

The extracted signal from the human body cannot be

fed to the circuit because it is very weak (around 0.5 mV).

For this reason an amplifier should be used to increase

the amplitude of the signal

Filter the noise from the amplified signal , the band pass filters were selected to cancel the noise that surrounds that signal and any value that is close to zero, which will be considered a DC signal. Furthermore, the filter will select a specific range in a signal, which starts from 0.5Hz up to a maximum value of 175 Hz . The filter circuit has been designed based on specific values of bandwidths as shown below.

Count the most significant peak using a comparator which compares a signal voltage applied at one input of an op-amp with a known reference voltage at the other

input . The next step would be to count the number of square pulses by giving the square waveform as an input

to the 4-bit synchronous counter . The output from the 4-bit synchronous counter which represented the number of heart pulses in 10 seconds

The output viewed through oscilloscope and 3 digits of 7

segment display where it's known that the maximum

heart rate might exceed 200 which is 3 digits numbers .

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