Height Sensor

Height sensors measure the distance between a point on a moving body and the ground. Cars and planes use them all the time! On cars, your suspension system uses height sensors to determine how high your seat is off the ground. When you go over a speed bump, your sensors will adjust the height difference so you feel perpendicular to the floor.

Similarly, the CoDrone uses IR sensors to determine its height. It sends and receives IR waves, and then measures the time between sent and received signals to process the height from the time given. It’s like how dolphins use sonar or bats use echolocation to identify their surroundings.

get_height() is a function that gets the current height of the drone from the object directly below its IR sensor. It then returns the current height above the object directly below the drone’s IR height sensor as an integer in millimeters.

Here’s an example code:

import CoDrone
drone = CoDrone.CoDrone()
drone.connect()
drone.takeoff()

# fly between 500mm and 1000mm

for i in range(200):
    height = drone.get_height()
    if height > 1000:
        drone.go(Direction.DOWN)
    elif height < 500:
        drone.go(Direction.UP)
    sleep(0.1)

drone.land()

After the drone takes off, the sensor will get the height. If the height is greater than 1000 millimeters, the drone will fly down, and if the height is less than 500 millimeters, the drone will fly up. It will then hover and land.

In general, using get_height()requires you to use if statements or loops so the height sensor can get continuous information and so your CoDrone can perform a certain action based on sensor readings.

• Always make a variable to get the value from drone.get_height()so you can use the variable for any task. In the program from the last step, we named ours height.
• The height sensor uses IR waves, which can sometimes be inaccurate! If you’re using the sensor on a reflective or glossy surface, the IR waves do not reflect correctly. Sunny areas can sometimes be an issue: sunlight carries IR waves, which means the IR receiver on the CoDrone is receiving extra IR waves and could throw off your reading.

Let’s see how accurate the height sensor is with this activity. For supplies, you’ll need a measuring tape or meter stick. In your program, you will need a while loop and a way to print the height. Once you’re finished, see if the printed height matches up to the height that you measure out.

Here’s an example:

import CoDrone

drone = CoDrone.CoDrone()
drone.pair()

while True :
    height = drone.get_height()
    print("Height:", height)

Use empty boxes and make a small staircase with at least 3 steps. Then, make a function that has the CoDrone continuously go forward while checking the height of the CoDrone. If the height of the CoDrone is less than 100 millimeters, the CoDrone needs to throttle upwards. This motion of going forward, up, and forward gives the CoDrone a “stepping” motion like going up a staircase.

go_to_height() is a setter function that will make the drone fly to the given height above the object (usually the ground) directly below its IR sensor. This function uses the IR sensor to continuously check the height, and it’s effective between 20 and 2000 millimeters.

To set the height, use a number between 20 and 2000 in the parentheses. For example, if you wanted your CoDrone to go to 1 meter, or 1000 millimeters, you would write:

go_to_height(1000)

Make a code to have your CoDrone hover at a height where you are able to run underneath of it as many times as possible before it falls. One problem: actually running underneath of your CoDrone will cause the height to change, so you will need to run next to it instead.

Check out the example code:

import CoDrone
drone = CoDrone.CoDrone()
drone.pair()

# go to 1600mm or 1.6m or 5.25 ft
drone.go_to_height(1600)
drone.hover(10)

drone.land()
drone.close()

You and/or your group will need to build a ladder out of PVC pipes like the one pictured. Your goal is to safely pass through all three windows (hint: try doing this in a zig-zag or spiral!) using a combination of get_height()and go_to_height(). Define a function to run this activity, and you can use if/else statements, for loops, and while loops if needed.

Building the ladder

Items:

• 16 h of PVC piping* (either ½ inch or ¾ inch diameter is fine)
• 8 Tee connectors*
• Two 90-degree elbows*

*Make sure they are all the same diameter! (I.e. buy them all ½ inch or all ¾ inch)

Instructions:

Cut the PVC pipes into ten 12 inch-long pipes and assemble.

OR

You can make the ladder out of tape and draw the squares to be 10 inches x 10 inches

Make an obstacle course with obstacles at various heights. You can use tables, chairs, books, and anything that isn’t fragile. Once you make the course, make a path for the CoDrone. The CoDrone should go over an obstacle or below an obstacle. These courses vary depending on the room so there is no correct answer. Get used to using go_to_height(), get_height(), and the previous lessons. Have fun!

For this activity, you’ll be playing reverse limbo! Instead of going under the bar, the CoDrone has to go over the bar! Start the bar at the lowest height and work your way up. Measure the height that you set the bar to. Using that measurement, you’ll need to use it in your code to program the CoDrone to pass over that height. If you touch the bar, you lose!