3.3: Temperature and Air Pressure

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. Describe what temperature is measured by the CoDrone EDU’s temperature sensor
2. Explain the importance of the temperature measurement
3. Convert temperature measurements to different units
4. Describe what a barometer is and how it can be used to measure height
5. Use barometer measurements to predict the height of the drone

Steps to Success:

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

Create a variable called temperature that will store the drone’s internal temperature. Attach it to the get_drone_temperature()block from the senior “Sensors” menu. Next, include a print block that will print temperature’s value. Use the dropdown menu to select the units. Run the program to see how hot it is inside your drone. Are you surprised by the results?

Fun fact: most of the world uses Celsius to measure temperature, and under 10% of countries use Fahrenheit. Although the function can return units in Fahrenheit, Celsius, or Kelvin, it may be useful to do the conversion yourself. From the “Functions” menu, grab the second return function block and name the function “to_Fahrenheit”.

Click the gear icon to add an input. Drag the input in the inputs block. This function will take in a parameter of degrees in Celsius that the function will convert into degrees Fahrenheit.

The equation to convert Celsius to Fahrenheit is degrees_F = degrees_C * 1.8 + 32. Create a variable degrees_F to store the output of the calculation. Don’t forget to return the variable from the function!

The last step is to call the function in a program. Take a temperature reading in Celsius and print the results. Then, print the converted value.

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 due to 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.

CoDrone EDU has a pressure sensor, also known as a barometer, built in to measure the air pressure around the CoDrone EDU. 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 EDU’s starting pressure is! Create a variable called pressure that will store the drone’s air pressure using the get_pressure() function from the “Sensors” menu. The default units for pressure are in pascals, which is the international standard for air pressure measurement. Then, print the value. Try running your program while holding your drone at various heights. What do you notice about the difference in air pressure?

You can also change the units of air pressure to millibar. One millibar is 100 pascals! What other units of air pressure can you think of?

Create a pressure variable that will get and store the air pressure at ground level. You will be creating multiple pressure variables, one for each height you want to measure the air pressure at. Create unique variables names to identify the different heights. For example, the first reading can be called pressure1.

Add a takeoff to your code and take a second pressure reading. Don’t forget to add the land command.

After taking off, throttle up at 30% speed for 1 second. Create a new variable to store the value.

Finally, add a print statement at the end to see the results. Are the differences in pressure large or small?

For this challenge, you will create a relationship between height and barometer measurements. Grab a partner for this activity to take measurements more easily. Here are the steps:

• In a forever loop, write code that will print the barometer sensor data when the space bar is pressed.
• Find a ruler or measuring tape to use for measuring the drone’s height. This is easier with a partner so that they can hold the measuring tape for you.
• Run your program so that it’s ready to receive key press commands.
• Move the drone with your hand to various heights. For example, measure 6 inches off the ground, 12 inches, 18 inches, etc. Press the space bar at each reading and record the result.

Finally, analyze the results. How sensitive is the barometer? Can you figure out a relationship between the pressure and height? In other words, what is the difference in pascals for every 6 inches?

In this lesson, you learned about the CoDrone EDU’s temperature sensor and barometer. The temperature sensor and barometer can help you observe important info about the CoDrone EDU’s environment and status! These sensors are also used to estimate height and altitude.