Battery Checker

Think of all the electronics that you use and how you know that their battery is low or dead on each of them. If you are on a laptop or phone, you will most likely see a battery icon on the top or bottom of your screen. There is also a battery life indicator on Blockly! Pair to your CoDrone and look on the bottom left of your screen. 

How can you tell if your CoDrone is running out of battery without looking at Blockly? In this lesson, you will be coding a part of your drone to display different battery percentages using if else statements and LED colors.

The “get battery percentage” block from the Sensors menu is probably the most important block for this lesson since it is the one that requests information from the CoDrone. In your case, it will request the battery percentage, which can range from 0 (completely out of charge) to 100 (fully charged).

To request battery percentage in a program, make a variable called battery from the variables menu. 

Once created, set it equal to the value that is returned from requesting the CoDrone for battery percentage.

You are going to use if else statements to check what the value of your battery level is. Depending on your battery level, your CoDrone’s eyes will turn a certain color. You can change them to whatever you want, but we recommend you make them easy to tell apart so you know when you need to charge your battery. This is what we’re going to use for this lesson: 

• 100-76: LEDs hold green 
• 75-51: LEDs hold yellow 
• 50-26: LEDs hold red 
• 25-0: LEDs blink red

To set your CoDrone’s eyes to green when the battery is 76-100%, connect an if else statement. Use a greater than block from the logic menu in the conditional space.

Drag and drop your variable into the first value box, and type 75 in the second white value box using a math block. 

What color should the LEDs be if the battery is above 75%? Change your drone’s lights to green in the “do” portion of the code.

For the next part, when the battery is 51-75%, you will need an else if statement. Remember that an else if statement will execute if the initial statement is false. To access this block, click on the blue gear from the if statement and drag an else if statement into the code block.

When the battery is between 50 and 75% percent full, what color should the LEDs be? Make sure to set them to the appropriate color!

For battery levels between 25 and 50% the LEDs will be red. This will indicate low battery but not enough to replace your drone battery just yet.

Repeat the same process with an else-if block and add your code to change the LEDs.

You will now use an else statement to indicate that if none of the above cases are true, your battery needs to be charged! This means that the battery percentage must be 25% or below. In this case, the LEDs should be blinking red. 

Add an else case by clicking the blue gear icon and code your LEDs.

Test your code to make sure that it works! To do this, remove the request block from the variable block and enter in any number from 0 to 100. If your code works, your CoDrone’s eyes should change to the color that matches the battery level you put in. Once you know all of the colors are displaying the way they should, you can put the request battery block back into the variable block. 

In this example. the code is tested with a value of 45. What color should the LEDs be?

The previous code will only check the battery once: at the moment that you run your program. If you want to continuously check your battery, while flying for example, you need to have all that code in a loop. 

Wrap your code in a while loop that checks if the code is running.

Activity: Low Battery Landing 

Have your CoDrone safely land when the battery is too low! 

Rules: 

1. Make a code that will land the CoDrone when the battery is less than 20%. 
2. Crashing does not count as a safe landing!