Case 01: LED
3. Case 01: LED#
LED lights are used widely in urban construction with a wide range of applications such as traffic lights at intersections, shop billboards, park signage lighting, shopping mall lighting and more. In this lesson, we will control the 2 LEDs to make an alternative flashing with the Pico:ed.
3.2. Components List#
1 × Pico:ed
1 × USB Cable
1 × Breadboard Adapter
1 × 83×55mm Breadboard
2 × LEDs
2 × 100Ω Resistors
N* Dupont Cables
3.3. Main Components#
The breadboard adapter allows all the pins of the Pico:ed to be led out on the breadboard, making it easy to create simple circuits there.
This below picture shows how to connect the breadboard adapter with a breadboard. And the adapter suits for breadboards in all sizes.
LED is the abbreviation of Light Emitting Diode. This is a semiconductor diode. It converts electrical energy into light energy. When an electric current passes through it, it glows.
If you look closely at an LED, you will find two characteristics. One is that the pins are not the same length and the other is that one side of the LED is flat, rather than cylindrical. These features tell you which pin is the anode (positive) and which pin is the cathode (negative). The longer pins are connected to the positive supply (3.3v) and the pins with the flat side are connected to ground.
A resistor is a component used to control current. It limits the current in the circuit to which it is connected. In our experiments, we used a 100ohm resistor. If the current is not restricted, it will damage the LEDs.
Would you like to identify the resistance value by its colour ring? You can read this article: How to Identify Color Circle Resistance Value
Connect all your components as the pictures describe:
Connect the shorter pins of the LED with the GND.
Connect the longer pin of one LED with the P0 and another with P1 through the resistors.
See the picture after connection:
Program Preparation: Prpgramming environment
# Import the modules that we need: import board import digitalio import time # Set the connencted pins and their directions of the LEDs led_0 = digitalio.DigitalInOut(board.P0_A0) led_1 = digitalio.DigitalInOut(board.P1_A1) led_0.direction = digitalio.Direction.OUTPUT led_1.direction = digitalio.Direction.OUTPUT # Set the 2 LEDs turn on and off. while True: led_0.value = True led_1.value = False time.sleep(1) led_0.value = False led_1.value = True time.sleep(1)
Details of the Code:#
Import the modules that we need.
boardis the common container, and you can connect the pins you’d like to use through it. The
digitaliomodule contains classes to provide access to basic digital IO.
timeis the module contains the fuction of time setting.
import board import digitalio import time
Set the connected pins and the directions of the 2 LEDs.
led_0 = digitalio.DigitalInOut(board.P0_A0) led_1 = digitalio.DigitalInOut(board.P1_A1) led_0.direction = digitalio.Direction.OUTPUT led_1.direction = digitalio.Direction.OUTPUT
If the pins you are using are not P0_A0 and P1_A1, the other pin numbers can be viewed by entering the following code in the shell window below the Thonny editor.
>>> import board >>> help(board) object <module 'board'> is of type module __name__ -- board board_id -- elecfreaks_picoed BUZZER_GP0 -- board.BUZZER_GP0 I2C0_SDA -- board.BUZZER_GP0 I2C0_SCL -- board.I2C0_SCL BUZZER -- board.BUZZER BUZZER_GP3 -- board.BUZZER P4 -- board.P4 P5 -- board.P5 P6 -- board.P6 P7 -- board.P7 P8 -- board.P8 P9 -- board.P9 P10 -- board.P10 P11 -- board.P11 P12 -- board.P12 P13 -- board.P13 P14 -- board.P14 P15 -- board.P15 P16 -- board.P16 SDA -- board.SDA P20 -- board.SDA SCL -- board.SCL P19 -- board.SCL BUTTON_A -- board.BUTTON_A BUTTON_B -- board.BUTTON_B SMPS_MODE -- board.SMPS_MODE VBUS_SENSE -- board.VBUS_SENSE LED -- board.LED P0_A0 -- board.P0_A0 P0 -- board.P0_A0 A0 -- board.P0_A0 P1_A1 -- board.P1_A1 P1 -- board.P1_A1 A1 -- board.P1_A1 P2_A2 -- board.P2_A2 P2 -- board.P2_A2 A2 -- board.P2_A2 P3_A3 -- board.P3_A3 P3 -- board.P3_A3 A3 -- board.P3_A3
While true, set the status of the 2 LEDs as turning on and off. And you can use
Falseas the on and off switches of the LEDs.
while True: led_0.value = True # 1 led_1.value = False # 0 time.sleep(1) led_0.value = False # 0 led_1.value = True # 1 time.sleep(1)
The 2 LEDs light on alternately and if this is not the case, please check your applications.
How to simulate the traffic lights with 3 LEDs?