3.7 – Color Sensor

Make sure that your drone is connected with Blockly before starting the lesson! If you are unsure of how to connect, go back to lesson 1.1 to review!

Goals:

By the end of this lesson, I will be able to:

1. Know the difference between HSV and RGB
2. Describe how the CoDrone EDU classifies colors
3. Calibrate my color sensor
4. Predict colors with the CoDrone EDU

Steps to Success:

1. Color Sensor Calibration
2. Color Sensor Prediction
3. Color Piano
4. Challenge 1: Multiple Samples
5. Challenge 2: Color Piano – Extended

Important: The color sensors will only work if the drone has landed on a surface. The color sensors cannot detect the surface underneath during flight.

Your drone will return color data in the HSV color space. HSV stands for hue, saturation, and value.

• Hue represents the color as a value from 0-360
• Saturation is the color’s intensity from 0-100
• Value is the lightness or darkness of the color from 0-100

For computer recognition and other robotics applications, it is better to use the HSV color space, since it separates values for colors and intensity. This is important because shadows, reflections, and other factors may cause certain colors to look very different. The HSV color space takes this into account for more accurate results.

Let’s start by finding how to access color data from the remote controller. First, make sure that you are not in the “LINK” state. To access color data from the controller, we need to be in remote control flight mode. Once in the remote control state, press either the “P” or “S” button until you see the screen in the image below. From this screen you can see HSV values (Hue, Saturation, Value) as well as the current color seen by the drone!

Place the drone on top of each of the 8 color cards that you received in the box. Sometimes, the color may be predicted incorrectly or return an unknown color. That’s ok! In the next step, you will learn how to calibrate the sensor and add new colors.

Open the “Colors” menu, click on the Calibrate color button to open the color calibration menu.

A window will appear with options to create a new dataset or add to an existing dataset. Since this is the first time, create a new color set.

Name your color set codrone_colors, or any other name that you will remember.

To calibrate your sensor, you need to collect color samples for each card. The first color by default is red. Place your drone on the red color card and click “Collect” to collect 10 samples. Then, click the next label “yellow”. Once the label is selected, place your drone on the yellow color card and click “Collect” again. Repeat until you have at least 10 samples of each color. You can always add more data, but make sure you are taking samples of the color that matches the label.

When you are done, click “Calibrate”. Test your color set by placing the drone on each color card. After you finish testing, there are three button options.

• If you would like to redo the calibration, you can click start over to calibrate the color dataset again.
• “Use this color set” will create new blocks for you to use in your color set.
• “Download” will save a folder to your computer of all the color data to reuse later.

For this lesson, click “Use this color set”.

When you select this option, Blockly will add new blocks for you in the “Colors” menu. There will be a new block available for every color that you calibrated. Open the menu now to see these blocks. Your color calibration is complete and ready to use!

In this example, you will learn how to use the predict_color() with your dataset. From the “Colors” menu, drag the load classifier block into your workspace with the dataset you just created above.

In a loop that repeats forever (while code is running), create a variable that will store the predicted color returned from predict_color(). You can only use the green predict_color() block together with load_classifer. Finally, print the color to the console and wait 0.5 seconds. To test, run the code while placing the drone on each color card.

In this activity, you will modify your code to make your drone into an instrument! Every color will make a unique buzzer noise when it is detected. To do this, add a conditional statement that compares the predicted_color with a color label. You can find the color labels in the “Colors” menu. If the predicted color matches a designated color (like red), play a sound for a half a second!

To add more colors, click the blue gear icon and add more else if blocks. How many colors can you add?

As you add more conditional statements, remember that you can only use the labels that are in your dataset, or your drone may not be able to predict the colors correctly.

Light-up Piano

Add to your program and make the LEDs change color to match the color being detected.

Custom Landing Pads

Grab some markers and art supplies to design your own landing pads! Pick some new colors and use the color sensor calibration program to detect new colors.