Project Moussawiaa

Title: ECG Detector (Final Project) Authors: Abdulrasoul Moussawi, Ehab Badawood Affiliation: Undergraduate Department of Biomedical Engineering, EGRB 307: Bioinstrumentation Laboratory, Fall 2009. Virginia Commonwealth University. Richmond, VA 23220. Introduction: The aim of this lab was to design and build an ECG circuit that is able to acquire human’s ECG signal and enlarge it to a level sufficient for display and/or further processing. Each one of the partners should be able to acquire his/her own ECG signal and use it to count the average hart rate in heart beats per minute(bpm). Materials and methods: The ECG circuit was build up as shown in figure 1. This circuit contained three main parts. The first one was the main amplifier. It used both the passive high pass filter circuit and active low pass filter with gain. The input source was connected with sinusoidal waveform across the two input terminals. The second part was the pre-amplifier. It was build up and then it was connected to the main amplifier as shown in figure 1. The input pin of the main amplifier was connected to the out put pin of the pre-amplifier. This connection formed the entire ECG amplifier. The gain of the entire ECG amplifier was calculated and it was made sure that it was equal or more than 800. The third part of the ECG circuit that was build was the driven-right-leg circuit. It was connected to the point of B in the ECG circuit. Three clamp electrodes were used with cables for the measurement of the human ECG signal. The electrodes were clamped to the right hand, left hand, and right leg respectively. The ECG signal was observed from the output of the amplifier. This process was repeated with each one the group. Results: The resistances, the high pass filter, and the active low pass filter with gain were calculated using the formulas and given values in the laboratory manual. The lower corner frequency for the passive high pass filter circuit was given by the formula fc1= 1/ (2*pi*R1*C1) to calculate R1 since every thing else was given [1]. The higher corner frequency for the active low pass filter circuit was given by the formula fc2 = 1 / (2*pi*R3*C2) to find the value of R3, since every thing else was given [1]. The gain, of the non-inverting amplifier, was given so R2 was calculated by G=(R3/R2)+1. R4 was given as it was almost equal to R1. In the pre-amplifier, the gain was also given as about 12 and Rg was calculated as G=(49.4K Ω /Rg)+1. The measured parts of the ECG circuit, as mentioned in the laboratory manual, are all in tables and figures down in the appendix.

Laboratory Exercise 7 Date of experiment: Thursday, 29OCT2009

Discussion: The ECG circuit was connected to the oscilloscope. Three clamps were clamped to each individual’s right hand, left hand, and right leg. It was shown in the oscilloscope the signals of the individual’s heart rate. The frequencies, output voltages, gain, and hear beet per min were taken and compared for each one as shown down in appendix G. The circuit showed how the human heart signals could be detected by an oscilloscope through an electrical circuit. There was not much differences between the two individual in the rate of heart beat or the signal of the heart rate because both of them were healthy and almost in the same age. As known that there are so many factors that could affect the heart rate signal and the number of heart beats per minutes. The most obvious were age, gender, whether the individual smoke or none, whether the individual was athlete or not, whether the individual was nerves or relaxed, and so on.

Reference: [1] “Final Project” EGRB 307 Course Handout, Biomedical Engineering, Virginia Commonwealth University, 2009.

Laboratory Exercise 7 Date of experiment: Thursday, 29OCT2009

Appendix A: figure 1. C2 R3 +4.5V

Black (LR)

+4.5V

3

Vin + Vin -

Ra

B

7

8

--

2

4

-

7

AD741

A

6

AD620

Ro

White (RR)

2

+ 1

Ra

R4

R2

3

5

+

Vout 6

4

-4.5V

C1 R1

-4.5V

R4 4.5V 2

-

7 6

R5

AD741 3

+

4

-4.5V

Green (LL)

Electrodes

Figure 1 shows the circuit designed for ECG signal acquisition. Appendix B: calculated resistors of the main amplifier Resistors R1 R2 R3 R4

Values 306.6 kΩ 2.2 kΩ 158.4 kΩ 304.7 kΩ

Appendix C: low and high cutoff frequencies and their gains Low Cutoff frequency 0.519

High cutoff frequency 100.477

Gain of the main amplifier 75

Appendix D: frequencies and output voltages Laboratory Exercise 7 Date of experiment: Thursday, 29OCT2009

Gain of the preamplifier 12.9

Frequency (Hz) 0.5 10 20 100 105

Output voltage (V) 5.3 5.8 6.1 4.8 4.8

Appendix E: The frequencies and output voltages of the ECG Frequency (Hz) 5 20 25 40 70 100 105

Output voltage (V) 1.06 1.02 1 0.943 0.850 0.728 0.711

Appendix F: The frequencies, output voltages, and gain of the pre-amplifier Frequency (Hz) 0.5 10 20 100 200

Output voltage (V) 1.36 1.254 1.246 1.253 1.242

Gain 13.6 12.5 12.4 12.5 12.4

Appendix G: amplitude and all data collected from the ECG signal tests on Ehab and Abdulrasoul Name

Amplitude (V)

Abdulrasoul

1.24

Ehab

1.92

Time between QRS(s) 0.87, 0.80,0.60, 0.60 0.80, 0.65, 0.60, 0.60

Laboratory Exercise 7 Date of experiment: Thursday, 29OCT2009

Total time 2.87

Average HR(bpm) 83.62

2.8

85.71

Figure 2: Ehab’s ECG signal

Figure 3: Abdulrasoul’s ECG signal

Laboratory Exercise 7 Date of experiment: Thursday, 29OCT2009