3.6: Front Range Sensor

Step 1

We've Moved!

We’ve moved to our new lesson portal: Robolink Learn! Lessons here will remain available until the end of June 2026. This version of Basecamp will no longer be updated and uses outdated references to Blockly for Robolink. You can access the previous version of Blockly here.

Step 2

How Does the Front Range Sensor Work?

The front range sensor on your drone is the same sensor as the one on the bottom. Just like it was mentioned in the previous lesson, you will see two dots on the sensor. One of those emits the infrared light, and the other receives the infrared that is reflected from the surface. The chip calculates the distance based on the time it took for the infrared light to come back to the receiver.

Note: The maximum range for the front range sensor is 1.5 meters.

Step 3

Introduction to the Front Range Sensor

You can access the front range sensor data with the get_range() block in the “Sensors” menu. Start by printing the front range sensor value. Go to the “Sensors” menu and drag the get_range() function into your workspace.

frontrange-getrange-senior-cde-blockly-cm

To see the values, attach a print block. Then, add a sleep(0.5) sec block from the “Timing” category. Run all of this in a loop to repeat 20 times.

While running the program, slowly move your hand toward and away from the front range sensor.

Try changing the units by selecting millimeters or inches from the dropdown menu and repeating the experiment. As a bonus, grab a ruler or meter stick to measure the accuracy of the sensor.

Step 4

Safe Takeoff

Pilots often do a series of pre-flight checks to make sure that everything is working on their aircraft before attempting to fly. One thing to consider checking is making sure that the takeoff area is clear. Since CoDrone EDU has a front range sensor, you can automate this process! For our next program, the drone will only take off if there is not an object within 30cm (about 12 inches) in front of the drone.

Start by making a variable called distance. This variable will store the minimum distance in centimeters that should be clear in front of the drone. Since you only want the drone to take off if the there is no object in front within 30 centimeters, set the variable to 30.

Before taking off, use an if statement to check if the area is clear by comparing the data from the front range sensor (in centimeters) to the variable. Write a warning message if the sensor is detecting an object less than 30 centimeters away.

The if statement below will only return true if there is an object within 30 centimeters from the front of the drone. If that is not true, program an else statement to take off and then land. Make another print statement to state that the drone has been cleared for takeoff.

Step 5

Avoid an Obstacle During Flight

Now that preflight checks are complete, add in some flight movements! If the area is clear for takeoff. CoDrone EDU will take off and fly forward until it detects another obstacle.

You are going to add code to the else statement. Since you don’t know how long it will take for our drone to find an obstacle, include an infinite while loop. Add a while loop after takeoff.

While the sensor is reading any value greater than 30 centimeters, CoDrone EDU should keep flying. You can copy and paste the same conditional from earlier, but don’t forget to change the less/greater than sign the opposite way!

cdeb-blockly-frontrange1-while-loop-conditional

Add in the flight movement for CoDrone EDU to fly forward while there is no obstacle ahead. Since we are relying on sensor information to detect an obstacle, fly forward with precaution at a lower speed. Then, add a move()block without the seconds delay. If you add a delay, it will slow down the program, and you might crash into an obstacle before the sensor was able to detect it in time.

cdeb-blockly-frontrange1-while-loop-conditional-with-move

Finally, outside the loop, add a print statement and land. Here is the final code:

cdeb-blockly-frontrange1-while-loop-conditional-move-final

Step 6

Challenges

Challenge: Drone Basketball

For this challenge, make your own basketball hoop using a wall and hula-hoop or other materials. Your goal is to have CoDrone EDU go through the hoop after detecting the ‘backboard’, just like a basketball would! In order to complete the challenge, you must do the following:

Create your own basketball hoop for CoDrone EDU to fly through
Your program must have the CoDrone EDU fly towards the hoop, detect the wall/backboard, and fly through the hoop before landing

Challenge: Homing in

For this challenge, you will be programming your CoDrone EDU to fly as close to the wall as possible! Using the front range sensor, try and write a program that will stop the CoDrone once it reaches a certain distance from the wall; that distance will depend on where you are flying your CoDrone EDU, so make sure to test out different values!

Step 7

Lesson Complete

In this lesson, you learned how to use the CoDrone EDU’s front range sensor to detect how far an object is in front of the CoDrone EDU. It has many useful applications like building autonomous navigation programs and safety features.

This lesson works with:

Grade level:

Approx. time required:

We've Moved!

How Does the Front Range Sensor Work?

Introduction to the Front Range Sensor

Safe Takeoff

Avoid an Obstacle During Flight

Challenges

Lesson Complete

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