Understanding PWM for Motor and LED Control

Pulse Width Modulation (PWM) is a widely used technique in microcontrollers to control power delivered to devices such as motors, LEDs, and heaters. Instead of changing voltage directly, PWM controls the duty cycle of a digital signal to simulate analog output.

What is PWM?

PWM is a signal that switches between HIGH and LOW at a fixed frequency. The ratio of ON time to total period is called the duty cycle.

• 0% → always OFF
• 50% → half ON, half OFF
• 100% → always ON

How PWM Controls Output

Even though PWM is digital, devices respond to the average power.

Example:

• LED → brightness changes
• Motor → speed changes

Higher duty cycle → more power delivered.

PWM Parameters

Key parameters:

• Frequency → how fast signal switches
• Duty Cycle → percentage of ON time

Both affect system behavior.

PWM for LED Control

PWM allows smooth brightness control without changing voltage.

Advantages:

• Energy efficient
• Stable brightness
• No heat loss like linear control

PWM for Motor Control

PWM controls motor speed by adjusting average voltage.

• Low duty → slow speed
• High duty → fast speed

Used in:

• DC motors
• Fans
• Robotics

Practical Example

Using Arduino:

analogWrite(ledPin, 128); // 50% duty cycle (0–255)

Common Issues

• Wrong frequency → flickering or noise
• Low resolution → rough control
• Electrical noise in motor systems

Applications

PWM is widely used in:

• Motor speed control
• LED dimming
• Power regulation
• Switching power supplies

PWM is a powerful and efficient method to control analog behavior using digital signals. By adjusting duty cycle and frequency, microcontrollers can precisely control devices in various applications.

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