1. Arduino Analog I/O
Analog input pins: 0 – 5
Analog output pins: 3, 5, 6, 9, 10, 11 (digital pins)
Analog input functions
int val = analog Read(pin)
Converts 0 – 5v. voltage to a 10-bit number (0 –1023)
Analog Reference(type)
Used to change how voltage is converted (advanced)
Analog output
analogWrite(pin, value)
value is 0 – 255
Generates a PWM output on digital pin (3, 5, 6, 9, 10, 11)

2. AVR Architecture
Clocks and Power

3. The Arduino Microcontroller: Atmel ARV Atmega 328

4. IR Sensors
IR Sensors work by using a specific light sensor to detect a select light wavelength in the Infra-Red (IR) spectrum. By using an LED which produces light at the same wavelength as what the sensor is looking for, you can look at the intensity of the received light. When an object is close to the sensor, the light from the LED bounces off the object and into the light sensor. This results in a large jump in the intensity, which we already know can be detected using a threshold. In case no object, no light will received back as shown in figures

5. Detecting Brightness with IR Sensors
Since the sensor works by looking for reflected light, it is possible to have a sensor that can return the value of the reflected light. This type of sensor can then be used to measure how "bright" the object is. This is useful for tasks like line tracking.

6. Working of IR sensors

7. Shapes and Applications of IR Sensors