29 869
modifications
Modifications
Sauter à la navigation
Sauter à la recherche
Ligne 12 :
Ligne 12 : + + + + + + + + + + + + + + + + + + + + + + + + + + +
→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.
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.
{{SPARKImage|Spark.IO-Core-LED-00.jpg|480px}}
{{SPARKImage|Spark.IO-Core-LED-01.jpg|480px}}
== Valeur de la résistance ==
But wait, what's the value of the resistor again?
''Here's how we find that out:''
According to [http://fr.wikipedia.org/wiki/Loi_d%27Ohm 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
{{underline|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)
{{Spark-Core-Hacking-TRAILER}}
{{Spark-Core-Hacking-TRAILER}}