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<b> Biomedical Engineering Design I</b>

<b> Research and Simulating EOG’s circuit of contactbio-signal meter </b>

<b>Tống Quang Minh_20213678Lê Thị Hà Phương_20213679Văn Thị Thu Trang_20213684</b>

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Hà Nội, 8-2022

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<small> </small> CONTENT

<b><small>1. INTRODUCTION...4</small></b>

<b><small>2. IDEA ABOUT APPLY EOG INTO TRAFFIC SAFETY ...7</small></b>

<b><small>3. RESEARCH ABOUT EOG’S CIRCUIT...10</small></b>

<b><small>4. STIMULATING AND RESULT...12</small></b>

<b><small>5. OUR ORIENTATION ...17</small></b>

<b><small>REFERENCES ...18</small></b>

<b> </b>

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<b> </b>

<b> </b>

<b>LIST OF FIGURES</b>Figure 2.1: Anti-drowsy steering wheel...8

Figure 2.2: Anti-drowsy chair...8

Figure 3.1: EOG CIRCUIT...9

Figure 4.1: Stimulate EOG circuit...12

Figure 4.2: Panels placing spots...13

Figure 4.3: Bandpass Filter Circuit...14

Figure 4.4: The output when frequency is 30 Hz...15

Figure 4.5: The ouput when the frequency is 1000 Hz...16

Figure 4.6: Instrumental amplifier circuit...17

Figure 4.7: Instrumental Amplifier Circuit...17

Figure 4.8: Signal before and after amplified with gain equal 50100...18

Figure 4.9: IA circuit with 2 layers of non-inverting amplifier... ..19

Figure 4.10: Signal output with 50000 gain...20

Figure 4.11: Bode plot of band pass filter...20

Figure 4.12: Bode plot of instrumental amplifier...21

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Overview about the EOG:

The EOG signal refers to the electrical activity recorded from the eyemuscles during eye movements. It provides information about thedirection and extent of eye movements. Here is an overview of the EOGsignal:

1. Signal Generation: The EOG signal is generated by the cornea retinalpotential, which is the electrical potential difference between the cornea andthe retina. This potential arises due to the movement of the eye muscles andthe resulting changes in the electric field.

2. Electrical Characteristics: The EOG signal is a low-frequency signal typicallyranging from a few hertz to a few tens of hertz. It consists of both directcurrent (DC) components and alternating current (AC) components.

3. Baseline and Eye Movements: The EOG signal has a baseline voltage thatrepresents the resting position of the eye. When eye movements occur, thevoltage of the EOG signal changes from the baseline, reflecting themovement of the eyes.

4. Bipolar Configuration: EOG signals are recorded using a bipolarconfiguration, where two electrodes are placed near the eyes. One electrode istypically placed near the outer canthus (lateral canthus) of each eye tomeasure horizontal eye movements. Another electrode is placed above orbelow the eye to measure vertical eye movements.

5. Signal Interpretation: The EOG signal can be analyzed to determine thedirection and magnitude of eye movements. By examining the voltagedifferences between the electrodes, researchers can infer the eye movementdirection (e.g., left, right, up, down) and estimate the amplitude of themovement.

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6. Calibration: EOG signals require calibration to establish a relationshipbetween the recorded voltage and specific eye movement parameters.Calibration involves having the participant perform controlled eyemovements or fixate on specific points, allowing for the translation of thevoltage values into meaningful eye movement measurements.

7. Signal Processing: EOG signals often undergo various signal processing stepsto enhance the quality of the signal and extract relevant information. Signalprocessing techniques may include filtering to remove noise, artifact removalto eliminate unwanted signals (e.g., blinks), and feature extraction to quantifyspecific characteristics of eye movements.

Reasons for choosing the topic:

1. About interdisciplinary nature: EOG sits at the intersection of multipledisciplines, including neuroscience, ophthalmology, psychology, computerscience, and human-computer interaction. Exploring EOG allows for a broadunderstanding of how these fields converge in studying eye movements andtheir applications.

2. Scientific research meaning: EOG has been a crucial technique in eyemovement research for many years. It has provided valuable insights intovarious aspects of visual perception, cognitive processes, sleep studies, andclinical evaluations. Understanding EOG can help appreciate the historicaland ongoing contributions of this technique to scientific advancements.3. Practical Applications: EOG has practical applications in diverse domains.

From clinical diagnosis and sleep research to human-computer interaction anddriver fatigue detection, EOG-based systems have real-world implications.Examining these applications can shed light on how EOG is being utilized toaddress practical challenges and improve various aspects of human life.4. Technological Advancements: EOG technology has evolved over time, and

recent advancements have made it more accessible, portable, and wearable.Exploring these technological developments, such as miniaturized

5. Can integration with eye tracking: EOG can be integrated with other tracking techniques, such as video-based or infrared-based eye trackers, to

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eye-improve accuracy and spatial resolution. Understanding the synergiesbetween EOG and other eye-tracking methods can provide a comprehensiveunderstanding of eye movement analysis.

6. Accessibility and Affordability: Compared to some high-end eye-trackingtechnologies, EOG is relatively affordable and accessible. It can beimplemented in various settings without requiring complex and expensiveequipment. This makes EOG an attractive option for researchers, clinicians,and developers working with limited resources.

7. Diagnostic and Clinical Utility: EOG has significant diagnostic and clinicalutility in assessing various eye movement disorders and neurologicalconditions. It can help diagnose conditions such as nystagmus, ocular motorabnormalities, and vestibular disorders. Exploring these clinical applicationscan provide insights into the role of EOG in patient assessment and treatment.8. Eye Movements and Cognition: Eye movements are closely linked tocognitive processes such as attention, perception, and decision-making.Studying EOG allows for a better understanding of how eye movementscontribute to cognitive functions, including visual search, reading, problem-solving, and memory. It can shed light on the intricate relationship betweeneye movements and cognition.

9. Sleep and Dream Research: EOG is widely used in sleep studies to investigatethe relationship between eye movements and sleep stages. By analyzing EOGsignals during sleep, researchers can identify rapid eye movementscharacteristic of REM sleep and understand the neural mechanismsunderlying dreaming. This area of research offers fascinating insights into thenature of sleep and dreaming.

10. Human Factors and Usability: EOG has implications in the field of humanfactors and usability. By studying eye movements through EOG, researcherscan assess visual attention, task performance, and user experience in variouscontexts such as interface design, advertising, product evaluation, andergonomics. Understanding the role of eye movements in human-computer

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interaction can inform the development of more user-friendly and efficientsystems.

11. Rehabilitation and Assistive Technology: EOG-based systems haveapplications in rehabilitation and assistive technology. They can be used todevelop interfaces and devices for individuals with motor disabilities,enabling them to control prosthetics, communicate, and access digitalenvironments using eye movements. Exploring EOG in the context ofrehabilitation can highlight its potential for enhancing quality of life andindependence for individuals with disabilities.

The goal to achieve:

1. Research and analyze the eye-neuron functions.2. To analyze the effect of the medicines and therapies.3. To analyze vision problems.

4. Apply EOG in finding and warning sleepy drivers.


<b>• According to statistics of the National Traffic Safety Committee, every year</b>

more than 6000 people die from traffic accidents related to dozing drivers. Sleepdeprivation accounts for 30% of all traffic incidents in a year.

• The fatigue and lack of sleep of the drivers of passenger cars, trucks, andcontainer trucks largely stem from professional pressure. Mr. Tran Huu Minh,Deputy Chief of Office of the National Traffic Safety Committee said: “TheRoad Traffic Law of 2008 stipulates that motorists driving long distances mustnot drive more than 10 hours a day and continuously for 4 hours. After every 2.5to 3 hours, the driver must take a break of 30-45 minutes before continuing todrive. However, because of professional pressure, many drivers ignore thisregulation. Also, according to Mr. Minh, in order to partly solve the problem,according to the orientation of the Ministry of Transport to 2030, there will be

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about 152 stops to help drivers take a break in the middle of the journey, notexceeding 4 consecutive hours in accordance with the Law. Road traffic.• In fact, in-depth research from the American Association for Traffic SafetyAAA shows that driving with less than 5 hours of sleep a day is just asdangerous as drinking while driving. The study also found that it is quitedifficult to detect drowsiness while driving, making this an urgent traffic safetyissue today.

Since then, many products have been launched in the world to serve thisproblem. For example: anti-drowsy steering wheel for driver [1], anti-drowsyseat [2], ....

Figure 2.1: Anti-drowsy steering wheel [1]

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Figure 2.2: Anti-drowsy chair [2]

- From there, we also came up with the idea of electro-optical - which helps toquickly detect and warn drivers who are drowsy and also in other medical fieldssuch as eye disease [3], and eye defects.


Several factors affect the ability to track eye movement including consistently and accurately, environmental conditions, pupil shape, skin and eye color, race, and interference from eyelids and eyebrows. An

electrooculogram (EOG) [4] can overcome many of these limitations.EOG signals result from measuring the cornea-retinal standing potential (CRP) of the human eye; the behavior of the eye is like an electric dipole having a positive pole at the cornea and a negative pole at the retina. The voltage difference created between the retina and cornea, known as CPR, creates an electric field around the eye.

Many different eye movements recording methods have been released but they are too expensive and time-consuming. As a result, much of the literature is focused on EOG systems due to easy setup, less fatigue, not block the user’s visions; however, it has disadvantages of requiring electrodes, decreased accuracy by drifting due to DC amplification, and

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blinking artifacts. The use of DC amplification causes the EOG signal’s baseline to “drift” when recording over a long period of time.

While the EOG signal varies based on the individual and the environment, generally accepted values are 50-3500m V for the signal’s amplitude and frequencies are continuous at about 50Hz. The low frequencies that the EOGruns on cause artifacts, interference, and noise in the biopotential recording.

To save energy, a passive BPF rather than an active BPF is used. Because passive filter does not draw current from the subject , so there are no safetyconcerns.

Furthermore, the next stage of the circuit input signals into an operational amplifier, the input impedance of the circuit is very high and protects the user from unsafe current levels.

The signal gathered from electrodes V are each first passed through <small>1-4</small>

separated but identical BPFs to reduce noise prior to the gain stage.o Instrumental amplifiers (IA):

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Separate but identical IAs is used to measure azimuth and elevation movement. 2.5V sources are used to power the IAs so that the device is relatively low power.

As mentioned before, EOG signals come in at around 50mV at their lowest and will be somewhat attenuated by the BPF, so we will aim to design for a differential gain (A ) of 50,000V/V. Our design has an A of 50,010 V/V. <small>DD</small>

Signals that come in with a larger amplitude may experience some clipping.o Active Grounding – Driven Right Leg (DRL)

A DRL is added to this circuit to compensate for the capacitive noise that is generated by ambient 60Hz AC sources by decreasing common mode voltage of the body. The DRL takes inputs from the IA measuring azimuth movement and feeds the output to the grounding electrodes on the forehead.

The DRL is used to reduce the common mode voltage input to both azimuth and elevation IAs, as the electrodes used to measure both movements are extremely close together and connected to the same subject.

o Common-mode rejection ratio (CMRR)

CMRR for this circuit is calculate by using this formula:and is approximately 102dB.

shows the equation for common mode gain (A ) where ideally the resistors <small>c</small>

should be within 1% tolerance. A is the differential gain from the IA.<small>d</small>


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Figure 4.1:Stimulate EOG circuit

We use LTspice to stimulate the shown circuit, we need some resistors,capacitors, an amp, and input collecting from the panels that place on a spot nearthe eyes according to the picture below.

Figure 4.2: Panels placing spots

However due to the lack of knowledge of stimulate the input signal, we replacethe input signal with an AC voltage source which variable show a waveformfigure.

The first thing that the signal come through is the bandpass filter, we mustunderstand how the bandpass filter work. The band pass filter is an electronicdevice or circuit that allows only pre-defined set of frequencies to pass through.It is a combination of a high pass filter and a low pass filter.

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Figure 4.3: Bandpass Filter Circuit

The picture above is a bandpass filter that we use to reject the frequencies thatwe don’t want to appear in our project.

As can be seen, the first half of the circuit which contains C and R is called a<small>11 </small>

High – Pass filter which filters the low frequencies and allows only thefrequency that is higher than the set high cut-off frequency. The value of thishigh cut-off frequency () can be calculated using the formula:

And in this situation with C = 10, R = 16k <small>11</small> m

The second half of the circuit which contains C and R is called a Low-Pass<small>2 2 </small>

Filter which filters the higher frequencies and allows only the frequency that islower than the set low cut-off frequency (). The value of low cut-off frequencycan be calculated using this formula:

And with C = 10 , R = 290 <small>2 2</small> m