3.1: LED

1. Goals:By the end of this lesson, I will be able to:
   1. Explain how an LED functions
   2. Describe how LEDs can be used to communicate
   3. Explain how RGB color values can be used to create primary colors
   4. Explain how to make a wide variety of colors by blending RGB values
   5. Use sequences to make the LED perform a variety of blinking patterns
   6. Use the LED to communicate information about a program while it runs
   7. Explain how the sleep function can be used to change the duration of LED on and off sequences

   Steps to Success:

   1. What is an LED?
   2. LED_color
   3. Need to Take a Break? Let’s Sleep On It!
   4. Program a Solid LED
   5. LED_pattern
   6. Program a Patterned LED
   7. Other LED Functions
   8. Challenge 1: Color Bar
   9. Challenge 2: Menu With Lights

LED stands for “light-emitting diode”. A diode is an electronic device that allows an electronic current to flow in only one direction. LEDs are beginning to replace traditional light bulbs because they are more efficient.

Your CoDrone Mini has 1 RGB LED on the main body. RGB stands for red, green, and blue. Using the three colors, you can create almost every color imaginable! Aside from making your drone look cool, LEDs provide another form of feedback. A solid LED means your drone is connected, while a flashing LED means the battery is low or CDM is disconnected from the remote.

The most basic LED function that you can use is LED_color. This function allows you to change the color of the LED built into the drone. Watch the video below to learn more about this function and its parameters:

Before we get started with the LED, we need to understand the sleep (seconds) function. This is part of the time  library which needs to be imported, just like we import the CoDrone_mini library. The sleep function takes in an integer or decimal value that represents the number of seconds you want the program to pause before it moves on to the next step. This is helpful to make sure the drone completes a movement, sequence, or procedure before moving on to the next step. It also allows us to see the results of the LED’s color change before it moves on to the next. Watch the video below to try an example of the sleep function:

Now that we know the purpose of the sleep function, let’s make a program that changes the drone’s LED color from red to green and then finally to blue:

import CoDrone_mini

import time



drone = CoDrone_mini.CoDrone()

drone.pair()



drone.LED_color(255, 0, 0, 100)   # Red     

time.sleep(1) 

drone.LED_color(0, 255, 0, 100). # Green

time.sleep(1)

drone.LED_color(0, 0, 255, 100). # Blue

time.sleep(1)

Once you have this program working, try playing with the sleep time and see what happens. You can even try decimal values!

If you’re done with your LED or want to set it back to its default, there are two functions for that:

• turn_off_LED(): turns the LED off. Perfect if you’re trying to go undercover.
• reset_LED() : resets the LED back to its default, which is solid red.

The turn_off_LED() function is especially useful to ensure our LED is not sending mixed signals when flying and communicating.

Now that we know the basics of using the LED, let’s add it to a flight program! For this challenge, you will create a program that has the drone fly to 3 different altitudes. At each Altitude, have the drone play a light pattern in a color of your choosing. Make sure that, for this challenge, you complete the following requirements:

1. Have the drone takeoff then fly to 3 different altitudes
2. Use 3 different colors (one at each altitude)
3. Pause for at least 3 seconds between each altitude level to give your lights time to play their sequence
4. Land  the drone once completed

One other important note:

If you decide to use an LED function before takeoff, make sure you sleep for at least 1 second before the takeoff command, otherwise, the program may miss LED command and it may not get displayed. See the code below for an example:

drone.LED_color(255, 0, 0, 100) 
time.sleep(1)       # Add a time.sleep(1) before takeoff
drone.takeoff()

For your second challenge, take the flight menu from Lesson 2.6 that you created and add LED light confirmations for each menu selection. For this challenge, your program must have the following:

1. 5 or more menu commands that are printed to the terminal (including the escape command)
2. Use 5 or more different colors (1 for each menu command)
3. Update the flight commands menu to include a description of the LED color and pattern for each command