# Lesson 5--Microduino “LED Brightness and Potentiometer PWM”

 Language: English  • 中文

## Objective

In the last lesson, we used a button to generate PWM to control the LED. Now, we will use a precision potentiometer to control the LED. The difference between the two is that a button uses a digital signal (0 and 1) to control the LED. A potentiometer uses an analog signal to generate PWM which is a linear change of state, so the LED's brightness can be changed clearly and gradually. Another downside of using a button is that electronic interference can cause unintended noise. That was why we had to add a pull-up/pull down resistor to our button.

## Equipment

• Microduino-Core
• Microduino-FT232R
• Other hardware equipment
• 1x Box of breadboard jumper wires
• 1x LED
• 1x 220Ω resistor
• 1x Precision potentiometer
• 1x USB Data cable

## Experiment Schematic

• Connecting the Potentiometer

The LED connects to any PWM output pin. The center pin of the potentiometer connects to analog ports A0 ~ A5. The potentiometer's other two pins connect to GND and 5V. The analog interface can measure 0-5V, and analogRead() returns corresponding values 0-1024.

## Program

```void setup()
{
pinMode(3,OUTPUT); //Choose the PWM output Port
}
void loop()
{
int val= analogRead(A0);      //Read the analog port A0's value（voltage range is 0-5V,corresponding value is 0-1204）
val = map(val, 0, 1023, 0, 255);
//We want to map the analog value（0~1024）to（0~255) since the max PWM value is 255.
analogWrite(3, val);
}```

### map() function

• Function: Maps a certain range of values to a different range
• Parameters: map(value, fromLow, fromHigh, toLow, toHigh)
• value: value to be mapped
• fromLow: Start value of source range
• fromHigh: End value of source range
• toLow: Start value of target range
• toHigh: End value of target range

## Result

As you turn the potentiometer, the LED's brightness changes gradually.