Exercise 1 - Blinking LED

LEDs (light-emitting diodes) are small and energy efficient lights that are used in many applications. In this exercise we will start with one of the easiest LED blinking circuit.

In this excercise, PIN3 is used to drive the LED on and off. The 220Ω resistor act as a current limiter to limit the current flowing through the LED. Depending on the specifications, LEDs need about 8mA to 20mA of current to light up.

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1. Connect a JUMPER WIRE to GND and 33J.
2. Connect a JUMPER WIRE to PIN3 and 38J.
3. Connect a 220Ω RESISTOR to 34H and 38H.
4. Connect the anode (longer) pin of the RED LED to 34G and cathode (shorter) pin to 33G.

Write and Upload the Blinking LED Sketch

In order to execute the sketch for this exercise, launch Arduino IDE then

Click File -> New.

A new sketch editing window will appear. Copy the whole block of code below and paste it into the new sketch window, overwriting the empty setup() and loop() that was pre-created. Ensure that the board selected is Arduino Uno and the right COM port is chosen according to “Board Selection” chapter.

void setup() {
    pinMode(3, OUTPUT);
}

void loop() {
    digitalWrite(3, HIGH);
    delay(1000);
    digitalWrite(3, LOW);
    delay(1000);
}

Click Upload, and the Arduino IDE will prompt you to Save sketch folder as. Enter Excercise_1 into the filename field and click save. Once saved, the Arduino IDE will start to compile the sketch. After the compilation is completed, the Arduino IDE will start to upload the compiled sketch into the STEMTera™ Breadboard. During this stage both yellow LEDs on the STEMTera™ Breadboard will start blinking indicating the Arduino IDE is uploading the sketch to the STEMTera™ Breadboard.

Understanding the Blinking LED Sketch

From the circuit, we know that PIN3 of the STEMTera™ Breadboard is connected to the 220Ω resistor and the Red LED. In order to turn on the LED, we need to instruct the STEMTera™ Breadboard to set PIN3 to OUTPUT in the setup() function.

pinMode(3, OUTPUT);

The pinMode() function shown above takes two parameters. The first parameter is the pin number and the second parameter is the mode of the pin. The above code instructs the STEMTera™ Breadboard to set PIN3 as OUTPUT.

Once PIN3 is configured as OUTPUT, we can then instruct the STEMTera™ Breadboard to either set PIN3 HIGH or LOW.

digitalWrite(3, HIGH);

The digitalWrite() function shown above takes two parameters. The first parameter is the pin number and the second parameter is HIGH or LOW. When a PIN is set to HIGH, the PIN will OUTPUT 5V. When a PIN is set to LOW, the PIN will OUTPUT 0V (no voltage and connected to GROUND).

In order to set an ON time or OFF time, we can add a delay in between ON and OFF using the following line of code after setting a PIN HIGH or LOW.

delay(1000);

This line of code instruct the STEMTera™ Breadboard to delay for 1000 ms (milliseconds).

When ON, DELAY, OFF, DELAY are executed in a loop, the result of this exercise is the LED blinking in 1000ms ON and 1000ms OFF pattern.