Medical Devices Lab
Exp no 1: Observation of Different Temperature Sensors (IR sensor, DHT11) with Arduino.
Objective: To compare the performance Infrared (IR) temperature sensor and a DHT11 temperature and humidity sensor using an Arduino microcontroller.
Components/Devices Used:
Arduino Uno (or similar Arduino board)
Infrared (IR) Temperature Sensor (e.g. MLX90614)
DHT11 Temperature and Humidity Sensor
Breadboard
Jumper Wires
USB Cable for Arduino
Computer with Arduino IDE
Power Supply for Arduino
Theory:
DHT11 Sensor: The DHT11 sensor measures both temperature and humidity. It contains a thermistor for temperature measurement and a capacitive humidity sensor for humidity measurement. The sensor outputs a digital signal on the data pin.
IR Temperature Sensor: The IR sensor, such as the MLX90614, is a non-contact thermometer that uses infrared radiation to measure temperature. It detects infrared energy emitted by objects and calculates their temperature based on the amount of IR energy emitted.
Circuit for DHT11
Circuit for IR Temperature Sensor
Arduino code for DHT11:
#include <dht.h> // Include library
#define outPin 7 // Defines pin number to which the sensor is connected
dht DHT; // Creates a DHT object
void setup() {
Serial.begin(9600);
}
void loop() {
int readData = DHT.read11(outPin);
float t = DHT.temperature; // Read temperature
float h = DHT.humidity; // Read humidity
Serial.print("Temperature = ");
Serial.print(t);
Serial.print("°C | ");
Serial.print((t*9.0)/5.0+32.0); // Convert celsius to fahrenheit
Serial.println("°F ");
Serial.print("Humidity = ");
Serial.print(h);
Serial.println("% ");
Serial.println("");
delay(2000); // wait two seconds
}
Arduino code for IR Sensor:
#include <Wire.h>
#include <Adafruit_MLX90614.h>
Adafruit_MLX90614 mlx = Adafruit_MLX90614();
void setup() {
Serial.begin(9600);
Serial.println("Adafruit MLX90614 test");
mlx.begin();
}
void loop() {
Serial.print("Ambient = "); Serial.print(mlx.readAmbientTempC());
Serial.print("*C\tObject = "); Serial.print(mlx.readObjectTempC()); Serial.println("*C");
Serial.print("Ambient = "); Serial.print(mlx.readAmbientTempF());
Serial.print("*F\tObject = "); Serial.print(mlx.readObjectTempF()); Serial.println("*F");
Serial.println();
delay(500);
}
Results:
Output of the DHT11 sensor
Circuit for DHT11
Output of the IR Temperature sensor
Circuit for IR Temperature Sensor
Exp No 2: Understanding Corneal Curvature: A Practical Approach with Keratometer.
Objective: To learn how to use a keratometer for measuring the curvature of the cornea and understand its implications in diagnosing and correcting refractive errors.
Anatomy of Eye
Cornea: The clear, dome-shaped surface that covers the front of the eye. It's the first structure through which light passes and plays a crucial role in focusing vision. The cornea provides a significant portion of the eye's optical power.
Iris: The colored part of the eye, controlling the size of the pupil and the amount of light that enters the eye.
Lens: Located behind the iris, the lens further focuses light onto the retina at the back of the eye.
Retina: A layer of cells at the back of the eye that senses light and sends signals to the brain through the optic nerve.
Optic Nerve: Transmits visual information from the retina to the brain.
The Role of Corneal Curvature in Vision
The cornea's curvature is pivotal in bending (refracting) light rays to focus them on the retina. The degree of curvature determines how effectively the eye can focus light. If the curvature is not ideal, it leads to refractive errors, meaning the light doesn't focus perfectly on the retina, affecting the clarity of vision.
Common Refractive Errors Related to Corneal Shape
Myopia (Nearsightedness): Occurs when the cornea is too curved or the eyeball is too long, causing light rays to focus in front of the retina. This results in difficulty seeing distant objects clearly.
hypermetropia (Farsightedness): Happens when the cornea is too flat or the eyeball is too short, leading to light rays focusing behind the retina. This makes it hard to see close objects clearly.
Astigmatism: This is caused by an irregularly shaped cornea or lens. Instead of having a uniform curvature, the cornea or lens has different curvatures, causing light to focus on multiple points around the retina. This leads to blurred or distorted vision at all distances.
Principles of Keratometry
Keratometry is a technique used to measure the curvature of the anterior (front) surface of the cornea.
Light Reflection: The device projects a series of illuminated rings or mires onto the corneal surface.
Measuring Reflections: The keratometer measures the reflection of these rings from the cornea. Since the cornea acts like a convex mirror, the characteristics of the reflected image (like size and spacing) change based on the cornea's curvature.
Calculating Curvature: The keratometer uses the information from these reflections to calculate the radius of curvature of the cornea. The principle is based on the law of reflection and geometrical optics.
Output: The result is typically given in diopters, which is a unit of measurement that indicates the optical power of the cornea. The device may provide readings for different meridians of the cornea, especially useful in assessing and diagnosing astigmatism.
Mathematically:
In a simplified model, if you have the refractive power (D) of the cornea and the refractive index (n), you can use the formula,
D= (n - 1)/r
where, r is the radius of curvature, n is the refractive index of the cornea relative to air.
Results:
Keratomer
Discussion:
SP (Spherical Power): This value reflects the overall refractive power of the cornea, assuming it has a spherical shape. It is typically given in diopters (D). The spherical power is primarily used to correct myopia (nearsightedness) or hyperopia (farsightedness) where the refractive error is evenly distributed across the cornea.
CY (Cylindrical Power): This represents the degree of astigmatism due to the difference in curvature between the flattest and steepest meridians of the cornea. It is also expressed in diopters. Astigmatism occurs when the cornea is not perfectly spherical (like a football) but has different curvatures (more like a rugby ball), leading to distorted or blurred vision.
AX (Axis): The axis indicates the orientation of the astigmatism in degrees, ranging from 0 to 180. It identifies the position of the flattest meridian of the cornea. For example, an axis of 90 degrees means the flattest meridian is vertical, and an axis of 180 degrees means it is horizontal. This information is crucial when prescribing cylindrical lenses to correct astigmatism.
R1 and R2: These are the measurements of the principal meridians of the cornea. Keratometers typically measure the two most different curvatures on the cornea, which are perpendicular to each other. R1 and R2 represent the radius of curvature for these meridians, usually given in millimeters. From these values, the keratometer calculates the corneal power in diopters for each meridian. The difference between R1 and R2 helps to determine the amount of corneal astigmatism.
R1: Usually corresponds to the flatter (or least curved) meridian.
R2: Usually corresponds to the steeper (or more curved) meridian.
Exp no 3: EEG Exploration Using Emotiv Device
Objectives:
Understand the basics of EEG and its applications.
Gain hands-on experience with the Emotiv EEG device.
Learn how to set up electrodes and calibrate the device.
Perform simple cognitive tasks and observe corresponding EEG patterns.
Materials used:
Emotiv EEG device
Computer with Emotiv software installed:
Theory:
Electroencephalography (EEG) is a method to record electrical activity of the brain. It involves placing electrodes on the scalp, which pick up electrical signals produced by brain cells (neurons) communicating with each other.
The brain's electrical activity is always changing, and these changes reflect different mental states and processes. EEG captures these variations in voltage, allowing us to see brainwave patterns.
Brainwaves:
Nature of Brainwaves: Brainwaves are patterns of neuronal activity in the brain. They are crucial for understanding brain function and are associated with different states of consciousness, like sleep, relaxation, alertness, and problem-solving.
Significance: Analyzing these waves helps in understanding various brain disorders, mental states, and cognitive processes. It's key in diagnosing conditions like epilepsy, sleep disorders, and brain injuries.
Different Frequency Bands:
Delta Waves (<4 Hz):
Characteristics: Slowest brainwaves, high amplitude.
Associated With: Deep, dreamless sleep, and unconsciousness.
Significance: Important in healing and regeneration.
Theta Waves (4-7 Hz):
Characteristics: Found between sleep and wakefulness.
Associated With: REM sleep, meditation, creativity, and memory formation.
Significance: Often linked with emotions and subconscious mind.
Alpha Waves (8-13 Hz):
Characteristics: Present in relaxation, light meditation.
Associated With: Relaxed but awake state, often with closed eyes.
Significance: Important for stress reduction, well-being, and overall mental coordination.
Beta Waves (13-30 Hz):
Characteristics: Dominant during waking state, particularly active thinking, problem-solving.
Associated With: Alertness, concentration, cognition.
Significance: Vital for engaged mental activity, but high levels may indicate anxiety or restlessness.
Gamma Waves (>30 Hz):
Characteristics: Highest frequency, low amplitude.
Associated With: High-level information processing, insight, consciousness.
Significance: Crucial for cognitive functioning, learning, and memory.