Fig. 1 - Arduino: Lesson 6 - How to use analog output to fade an LED

Welcome to Lesson 6 - Basic Arduino Course

In today's lesson, we will learn how to use an analog output to increase and decrease the brightness of a LED. In this example, we will use the analogWrite() function, which triggers a PWM wave on an Arduino pin.

We will use PWM to vary the brightness of a LED as an example, but nothing prevents us from also using it to drive a motor and control its speed, the concept is the same.

The analogWrite() function triggers a square wave at the specified duty cycle until the next analogWrite() call.

The frequency of the PWM signal is around 490 Hz on most Arduinos, however on Arduino Uno and some similar boards, pins 5 and 6 use a frequency of about 980 Hz.

On most Arduino boards with ATmega168 or ATmega328 chips, this function works on pins 3, 5, 6, 9, 10 and 11. On the Arduino Mega this function works on pins 2 to 13 and 44 to 46.

Hardware Required

• Arduino Board
  
• LED
• 200 ohms resistor
• Jumper Wires
• Protoboard (optional)

The Circuit

The circuit is quite simple, we connect a LED in series with a 220 ohm resistor used to limit the current in the LED as we learned in the previous lessons, and we connect the PWM 9 port of the Arduino UNO as shown in Figure 2 below.

Fig. 2 - Using an analog output to fade an LED - tinkercad.com

We use a Protoboard to facilitate the connections, but you can also connect the wires directly to the Arduino.

The Code

The analogWrite() function writes an analog value to the Arduino pin. It is important to remember that this output is not a pure analog output that we can use to generate a pure sine wave, but this output is a PWM wave control.

When we execute the call to the analogWrite() function, the pin will generate a constant square wave with the specified duty cycle until the next function call.

After building the circuit, connect your Arduino board to your computer, launch Arduino Software (IDE), copy the code below and paste it into your Arduino IDE. But first let us understand the code line by line. 

• In Line 3, we declared ledPin to digital Pin 9 where we connect the LED to the digital Pin 9. 
• In Line 5, we enter the void setup() function. This function is read only once when the Arduino is started.
• In Line 6, we define Port 9 as the output, using the pinMode(); function;

• In Line 09, we enter in the loop() function does precisely what its name suggests, and loops consecutively.
• In Line 11, the control structure For, is used to repeat a block of statements enclosed in curly braces. An increment counter is usually used to increment and terminate the loop.
  
  
• In Line 12, we run the analogWrite() function, this function writes an analog value (PWM wave) to pin 9, in this case we are increasing the PWM value from 5 to 5, to increase the LED brightness up to the maximum value of 255.
• In Line 13, we use the function delay(); to wait for 30 milliseconds to see the dimming effect.

The complete code is showed in the sketch below!

Fig. 1 - Arduino Lesson 5 - Reading Potentiometer and Showing Values On Serial Monitor

Welcome to Lesson 5 - Basic Arduino Course

Today we are going to learn how to read a Potentiometer end showing the Values on Serial Monitor.
In this example, we will use a potentiometer, however, this same concept is used for most analog sensors. 

What will differentiate will be the type of calculation used, with reference to each sensor.

We will use the analogRead() function, to read A0 PIN, in Arduino we have 6 Analog Ports, which goes from A0 to A5, so we can make readings from up to 6 sensors simultaneously without having to use external hardware.

Hardware Required

• Arduino Board
  
• A 10K Potentiometer
• Wires
• Protoboard (optional)

Fig. 2 - Reading Potentiometer and Showing Values On Serial Monitor - tinkercad.com

The Code

The analogRead() function converts the input voltage range, 0 to 5 volts, to a digital value between 0 and 1023. This is done by a circuit within the microcontroller called analog-to-digital converter, or ADC.

Then, if the voltage at the center pin is 0 volts, analogRead() returns 0. When the shaft is turned all the way the other way, there is no resistance between the middle pin and the pin connected to 5 volts. 

If the voltage on the middle pin is then 5 volts, analogRead() returns 1023. In between, analogRead() returns a number between 0 and 1023 that is proportional to the voltage applied to the pin.

After building the circuit, connect your Arduino board to your computer, launch Arduino Software (IDE), copy the code below and paste it into your Arduino IDE. But first let us understand the code line by line. 

• In Line 3, we declared variable sensorPin which is set to Analog Pin A0 where we receive the value of the connected potentiometer. 
• In Line 4, we create a variable senorPin that stores the value of the sensor that we also use for the potentiometer.

• In Line 6, we enter the void setup() function. This function is read only once when the Arduino is started.
  
  
• In Line 7, we begin serial communication by declaring the Serial.begin() function. At 9600 bits of data per second, this is the speed at which your computer will communicate with your Arduino Serial.

• After setting the initializations, in Line 10 we will enter the void loop() function.
  
  
• In Line 11, we use the variable sensorValue to store the resistance value, which is between 0 and 10K (read by the Arduino as a value between 0 and 1023) and controlled by the potentiometer.
  
  
• In Line 13, we use the command Serial.println(), it is print out the value controlled by the potentiometer, this value will read with value between 0 and 1023 in your Serial Monitor.
  
  
• In Line 14, we run the delay() function, for greater system stability.

The complete code is showed in the sketch below!