This exercise uses the same hardware configuration as the previous LED (Digital) exercise. Note that there is a video at the end of this Section to aid with your understanding, as shown in Figure 1.

The exercise involves connecting an LED to a PWM-capable Arduino output pin and controlling its brightness using 8-bit PWM resolution, providing 256 discrete brightness levels.

Required hardware for this exercise:

• Arduino Uno board (supported by Simulink)
• USB Cable (Type A to Type B)
• Breadboard
• LED
• 220 Ohm resistor
• 2 x male-to-male breadboard wires

HardwareAssembly Steps

1. Connect digital pin 9 on the Arduino to a chosen column on the breadboard using a jumper wire.
2. Insert a 220 Ω resistor with one end in the same column as the wire from pin 9 and the other end in a different row.
3. Insert the LED such that:

• The long leg (anode) connects to the free end of the resistor.
• The short leg (cathode) connects to an Arduino GND pin using a jumper wire.
  

In this part of the exercise, you will develop a Simulink model to control the Arduino PWM output and vary the LED brightness. A sine wave signal is used to smoothly vary the PWM duty cycle between 0 (OFF) and 255 (fully ON).

Simulink Model Construction Steps

1. Add a Sine Wave block (from Sources) and connect it to an Abs (absolute value) block (from Math Operations).
2. Connect a Slider Gain block (from Math Operations), and set-up as following: The Slider Gain limits the maximum PWM value. For example, limiting the LED to approximately 2.3 corresponds to: 256 × 2.3 ≈ 117. For this exercise, set the upper limit to 255, corresponding to the full 5 output of the Arduino Uno.
3. Add a PWM block (from Common in the Simulink Support Package for Arduino Hardware) and connect three Scope blocks (from Sinks) to observe relevant signals.
4. Deploy the model using the same code-generation procedure as the previous exercise. Once deployed, observe the LED brightness variation and explore the effect of adjusting the Slider Gain.