3. case 01 led

3.1. Introduction


LED is a common use in our life. Most of signal light employs LED as main illuminant. In this case, we will use the micro:bit to control one LED flashing.

3.2. Hardware Connect


../../_images/jGkCj0K.png

  • Connect the circuit as above picture and put 2 AAA batteries into the batteries pack.

3.3. Principles of Circuits


../../_images/5DImBjP.png

  • The GND of slot on the micro:bit is into innards of batteries’ GND to generate the current loop.

  • Set low voltage(digital 1) to P0, the circuit on and the LED on.

  • Set high voltage(digital 0) to P0, the circuit off and the LED off.

3.4. Introduction of Components


LED

  • LED, light-emitting diode, is a solid state semiconductor devices, which can be directly converted into electricity for lighting up.

  • The experiment box included a red LED. The black port on the left is negative pole and the red port on the right is positive pole.

../../_images/ks4hn2r.png

- Note: Please note the positive and the negative when you are connecting.

Resistor

  • The resistor is a kind of component to control the current. It can limit the current of connecting circuit. By the way, there is no positive or negative for the resistor.

  • The experiment box included 3 100Ω resistors and 1 10KΩ resistor.

../../_images/fv1fyJm.png

  • Install a 100Ω resistor in LED circuit to limit the circuit. It may cause breakdown of LED if the current is not be limited.

3.5. Software


Step 1

../../_images/t34k5Zb.png

Step 2

  • First, snap the digital write pin into the forever block, write 1 to the P0 port for lighting up the LED, then pause 500ms;

../../_images/VOh783L.png

  • Next, snap the digital write pin under the pause (ms) block, write 0 to the P0 port for turning off the LED, then pause 500ms;

../../_images/D08SzOj.png

Program

---

3.6. Result


  • Turn on the switch, LED starts to flashing.

../../_images/KN0xKqX.gif

3.7. Think


  • Why we add a 500ms pause ?

3.8. Questions


3.9. More Information