Spark-Core-LED

Faire clignoter une LED

Blinking an LED is the "Hello World" example of the microcontroller world. It's a nice way to warm up and start your journey into the land of embedded hardware.

For this example, you will need a Spark Core (duh!), a Breadboard, an LED, a Resistor (we will soon find out a suitable value) and a USB cable.

Brancher

Connect everything together as shown in the picture. The LED is connected to pin D0 of the Core. The positive (longer pin) of the LED is connected to D0 via a resistor and its negative pin (shorter) is connected to ground.

Crédit: Particle.IO www.particle.io

Crédit: Particle.IO www.particle.io

Valeur de la résistance

But wait, what's the value of the resistor again?

Here's how we find that out:

According to Ohm's Law : Voltage = Current x Resistance

Therefore, Resistance = Voltage/ Current

In our case, the output voltage of the Core is 3.3V but the LED (typically) has a forward voltage drop of around 2.0V. So the actual voltage would be:

3.3V - 2.0V = 1.3V

The required current to light up an LED varies any where between 2mA to 20mA. More the current, brighter the intensity. But generally its a good idea to drive the LED at a lower limit to prolong its life span. We will choose a drive current of 5mA.

Hence, Resistance = 1.3V/ 5mA = 260 Ohms

Note:

Since there is so much variation in the values of the forward voltage drop of the LEDs depending upon type, size, color, manufacturer, etc., you could successfully use a resistor value from anywhere between 220Ohms to 1K Ohms.

In the picture above, we used a 1K resistor (Brown Black Red)

Le programme

Voici une version du programme proposé par Spark... avec les commentaires traduits pour faciliter la compréhension.

// Program to blink an LED connected to pin D0
// of the Spark Core.

// We name pin D0 as led
int led = D0;

// This routine runs only once upon reset
void setup()
{
  // Initialize D0 pin as output
  pinMode(led, OUTPUT);
}

// This routine loops forever
void loop()
{
  digitalWrite(led, HIGH);   // Turn ON the LED
  delay(1000);               // Wait for 1000mS = 1 second
  digitalWrite(led, LOW);    // Turn OFF the LED
  delay(1000);               // Wait for 1 second
}

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Source: Particle Core Examples créé par Particle.IO.

Traduction (et augmentation de contenu) réalisée par Meurisse D pour MCHobby.be - Translated (and enhanced) by Meurisse D. for MCHobby.be

Traduit avec l'autorisation de Particle.IO - Translated with the permission from Particle.IO - Particle.IO

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