4.3: Temperature and Air Pressure

Goals:

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

1. Describe what temperature is measured by the CoDrone Mini’s temperature sensor
2. Explain the importance of the temperature measurement
3. Create a program that can limit flight based on drone temperature
4. Convert temperature measurements to different units
5. Describe what a barometer is and how it can be used to measure height
6. Use barometer measurements to predict the height of the drone

Steps to Success:

1. Temperature Sensor
2. Print the Current Temperature
3. Temperature in Flight
4. Celsius to Fahrenheit
5. Barometer
6. Print the Current Pressure
7. More Pressure Readings
8. Pressure Readings and Lists
9. Challenge 1: Height Calculator Part 1
10. Challenge 2: Height Calculator Part 2

One of the sensors onboard CoDrone Mini is the temperature sensor, which does exactly what it says: it reads the temperature. However, it does NOT get the temperature from its environment, so it cannot be used to tell you whether it’s warm or cold where you are. What it can tell you is its internal temperature, so how cold or hot it is inside of the drone. This number will be in degrees Celsius.

Find out what your CoDrone Mini’s starting temperature is! Import the CoDrone Mini library, create the drone object, pair, and then create a variable called  temperature that will store the drone’s temperature after using the  get_drone_temp() function. Next, include a print statement that will print temperature’s value in degrees Celsius. 

import CoDrone_mini

drone = CoDrone_mini.CoDrone()

drone.pair()

temperature = drone.get_drone_temp()

print(temperature)

drone.close()

Run the program to see how hot it is inside of your drone. Are you surprised by the results?

One thing about batteries that you might already know: they heat up when they’re being used. You took your CoDrone Mini’s internal temperature while it was just sitting there, but what happens when it’s in flight and the battery is working hard to keep your drone in the air?

Import the CoDrone Mini library, create the drone object, and pair. Next, create a temperature variable (we called ours  start_temp ) and set it to get the drone’s temperature. Include a line to print the temperature before takeoff.

Have your drone takeoff, hover, and land. Next, create another variable to get the drone’s temperature, but name this one something different. we name ours  stop_temp . Include a line to print the temperature after takeoff. Remember, naming your variables is important. We should always give them meaningful names. In this case, start and stop or begin and end temps would be great, descriptive options. 

Finally, include code that will subtract the values from the two temperature variables and print the difference.

import CoDrone_mini

drone = CoDrone_mini.CoDrone()

drone.pair()


start_temp = drone.get_drone_temp()

print("Before taking off: ", start_temp)


drone.takeoff()

drone.hover(10)

drone.land()


stop_temp = drone.get_drone_temp()

print("After taking off: " , stop_temp)


diff_temp = stop_temp - start_temp

print("Difference: ", diff_temp)

drone.close()

Fun fact: most of the world uses Celsius to measure temperature, and under 10% of countries use Fahrenheit. If you’re in one of the Fahrenheit countries, or if you just want your CoDrone Mini to do some extra math, you can write a function to convert the Celsius input to degrees Fahrenheit.

def to_fahrenheit(degrees_c):

    degrees_f = degrees_c * 1.8 + 32

    return degrees_f

Try including this function in one of your programs! For example:

import CoDrone_mini

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

def to_fahrenheit(degrees_c):
    degrees_f = degrees_c * 1.8 + 32
    return degrees_f

temperature = drone.get_drone_temp()

print("Celsius: ", temperature)
print("Fahrenheit: ", to_fahrenheit(temperature))

drone.close()

In addition to the temperature sensor, the barometer can also measure pressure. You may have noticed that when you’re in the mountains or on a plane, your ears pop! The reason this happens is because there is air trapped in your inner ear. When you move up to a higher altitude, the air pressure is lower. This change causes pressure on your eardrum, which sounds and feels a lot like popping.

Our ears only pop with big differences in altitude. It probably wouldn’t happen if you went from the first floor of a building to the second floor. However, your CoDrone has a pressure sensor, also known as a barometer, built in to measure the air pressure around the CoDrone Mini. That sensor can detect seemingly tiny differences in height. Barometers are often used in weather forecasting since changes in air pressure can affect the weather. For example, a drop in atmospheric pressure means a storm is most likely on the way, while an increase in pressure usually predicts clear skies.

Find out what your CoDrone Mini’s starting pressure is! Import the CoDrone Mini library, create the drone object, pair, and then create a variable called pressure that will store the drone’s air pressure after using the  get_pressure() function. Next, include a print statement that will print pressure’s value in pascals, which is the international standard for air pressure measurement.

import CoDrone_mini

drone = CoDrone_mini.CoDrone()

drone.pair()

pressure = drone.get_pressure()

print("Pressure: ", pressure)

drone.close()

Try running your program with the CoDrone at different altitudes. What do you notice about the difference in air pressure?

Let’s take what you learned and see it in action! Import the CoDrone Mini and time libraries, create the drone object, and pair with your CoDrone.

Create a pressure variable that will get and store the air pressure at ground level. Important: you will be creating multiple pressure variables, one for each height you want to measure the air pressure at. You should either make their names memorable (like a variable called  pressure_ground ) or use numbers (like  pressure_1 ).

Program your drone to take off and then create another pressure variable. This will get the air pressure at the takeoff altitude.

Have your drone throttle up at 50% speed for 1 second. Create another pressure variable that will get their air pressure at this level. 

You can keep repeating the last step until you have all of the altitudes you need or your drone hits the ceiling — whatever comes first!

Finally, have your drone land. You should then include print statements so you can see the air pressure at all of the levels you included.

import CoDrone_mini

import time

drone = CoDrone_mini.CoDrone()

drone.pair()


pressure_1 = drone.get_pressure() # ground level


drone.takeoff()

pressure_2 = drone.get_pressure() # after takeoff level 1


drone.set_throttle(50)

drone.move(1)

pressure_3 = drone.get_pressure() # level 2


drone.move(1)

pressure_4 = drone.get_pressure() # level 3


drone.land()


print("On the Ground: ", pressure_1)

print("Level 1: ", pressure_2)

print("Level 2: ", pressure_3)

print("Level 3: ", pressure_4)

drone.close()

You will be using your program from the last activity but modifying it to use a list instead of four completely separate variables!

After importing libraries, creating the drone object, and pairing, create a list called labels and add the levels where you will be reading the drone’s air pressure. If you want to measure your drone’s air pressure at more or less levels, you will need to add or remove those from the list. Then create a variable called  pressure_data . This is what will store the air pressure’s values.

Add a command that will get the drone’s air pressure at ground level and then append, or add, that reading to your list. Since this is the first reading, this will go to the “Ground” label.

Add this same command after the drone’s takeoff, the throttle up after takeoff, and any other level where you decide to measure the air pressure. The readings will go to their respective labels in the list.

Add  time.sleep(0.05) so the program doesn’t skip over the landing command and then land your drone. 

Finally, print the length of your list with both the labels and their pressure data. Try graphing the results to see if you notice a pattern in your data!

import CoDrone_mini

import time

drone = CoDrone_mini.CoDrone()

drone.pair()


labels = ["Ground", "Level 1", "Level 2", "Level 3"]

pressure_data = []


pressure_data.append(drone.get_pressure()) # ground level


drone.takeoff()

pressure_data.append(drone.get_pressure()) # after takeoff level 1


drone.set_throttle(50)

drone.move(1)

pressure_data.append(drone.get_pressure()) # level 2


drone.move(1)

pressure_data.append(drone.get_pressure()) # level 3


time.sleep(0.05) # to prevent skipping land command


drone.land()


for i in range (len(labels)):

    print(labels[i], pressure_data[i])

drone.close()

For this challenge, we will first take, store and print barometer measurements. We will then attempt to correlate those to the height of the drone.

Define a function that takes readings and appends them to a list of pressures every second. You must use a loop to accomplish this. The function should take in a duration or number of readings as a parameter. Have the drone take off, call the function for a time of your choosing. Have the drone throttle up at a throttle level of your choosing for the duration that you chose (it is recommended to use a small number for both). Finally,  use a loop to print the values stored in the pressures. When you run your program, use something to measure the height of the drone at takeoff and the approximate height at each 1 second interval (you could use the number of blocks on the wall from the floor or a measuring stick or even your body).

Now that we have a list of pressures and heights, let’s figure out our conversion ratio. Complete the following calculation 3-4 sets of measurements you took:

height / pressure

This is your conversion ratio. Whenever you multiply this by a pressure, the Pascals will cancel and leave you with a height. Now that we know this ration, we will program it into the second part of our program:

Take your part 1 challenge program and add a function that takes in a list of pressure values and converts them to heights and then prints the list. You will need two loops for this function. Add the function call at the end of the program and then change the value of the duration. Run the program and watch your drone. Now check the the height values that were printed. Do the values printed out correspond to how high your drone flew? Would changing the throttle change the ratio we created? Why or why not?