3.6: Front Range Sensor

The CoDrone EDU is equipped with a front range sensor that can detect physical objects in front of it. The CoDrone EDU library has built-in functions that allow you to detect an object, avoid an object, or keep the same distance from an object. In this lesson, we are going to start by learning how to detect objects in front of our drone. The front range sensor can detect an object between 0–1000 millimeters (0–100 centimeters)

Let’s start by printing out our front range sensor value. We will do that by using the drone.get_front_range() function. This function will return a value in centimeters. So for example, if you print your front range sensor value, and it is 50, that means that it detects an object 50 centimeters away. Let’s do an example.

For this exercise, we won’t be flying our drone. Instead, we will run a program that prints out our front range sensor value once every second. Let’s use a for loop and print our sensor value 10 times!

Next, we need to use a for loop to print our front range sensor 10 times. We will also time.sleep(1) to make sure we’re only printing 1 value per second.

for i in range(10):
    print(drone.get_front_range())
    time.sleep(1)

Try running this program while slowly moving your drone toward or away from an object. This object can be your hand, a wall, a table, or anything big enough for your front range sensor to detect. The limit for the front range sensor is about 150 centimeters, or 1.5 meters.

Here is the full code for the program:

from codrone_edu.drone import *
import time
drone = Drone()
drone.pair()

for i in range(10):
    print(drone.get_front_range())
    time.sleep(1)
drone.close()

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 we may consider checking is making sure that our takeoff area is clear. The front range sensor on the CoDrone EDU can detect an object up to 1000 millimeters or 100 centimeters (~39 inches) away. Since we have that front range sensor, we can automate this process! For our next program, we will only take off if there is not an object within 500 mm (50 cm) of the front of our drone.

Let’s start by making a variable called distance. This variable will hold the range in centimeters that our front sensor will check for. In this example, CoDrone EDU will need 50 cm of clearance for takeoff.

distance = 50 

Implement a conditional to check if takeoff is clear.

if drone.detect_wall(distance):
    print("Takeoff area is not clear. Shutting down")

drone.detect_wall(distance) will only return true if there is an object within 50 cm from the front of the drone. If that is not true, then we will need to code for the “else” case. If there is no obstacle, the drone will take off and land.

else:
    drone.takeoff()
    drone.land()

Here is the full code for this program:

from codrone_edu.drone import *
drone = Drone()
drone.pair()

distance = 50

if drone.detect_wall(distance):
    print("Takeoff area is not clear. Shutting down")
else:
    drone.takeoff()
    drone.land()
drone.close()

Now that preflight checks are complete, let’s add in some flight movements! We can use our front range sensor to detect if we are approaching an object. Let’s add some code in our else case so that we fly forward until our drone spots an obstacle. Since we don’t know how long it will take for our drone to find an obstacle, we will use an infinite while loop and use break once we spot something. We will also use our movecommand in short bursts so that we can check for walls more frequently!

First, we create an infinite while loop, since we do not know how long it will take to find an obstacle.

while True:

Next, we will add in our flight movement and conditional check for obstacle detection. Since this while loop is continuously running, if we make our move command execute for a short amount of time, then our conditional check for an obstacle will run more frequently. You could think of this as your drone is closing its eyes for the amount of time you give it a move command. The shorter the drone has its eyes closed, the more frequently it can open its eyes to check for an obstacle.

drone.set_pitch(30)
drone.move(0.2)
if drone.detect_wall(distance):
    print("Object detected")
    break

We also add a break at the end of our conditional check to make sure we exit that infinite while loop we made!

Lastly, all we need to do is print a message indicating that an obstacle was found and send the drone a land command.

Here is the completed code for this lesson:

from codrone_edu.drone import *
drone = Drone()
drone.pair()

distance = 50

if drone.detect_wall(distance):
    print("Takeoff area is not clear. Shutting down")
else:
    drone.takeoff()
    while True:
        drone.set_pitch(30)
        drone.move(0.2)
        if drone.detect_wall(distance):
            print("Object detected")
            break
    print("Obstacle detected.. Landing!")
    drone.land()
drone.close()

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!

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. This has a variety of uses, ranging from obstacle avoidance to motion detecting!