Lesson 11 40 mins

Barometer is an in-built sensor on Pluto

WHAT IS A BAROMETER? (10 mins) 

Students can be given an example of change in air pressure at sea level and at a mountain. We can sense that change in air pressure which is evident from the headache or nausea at high altitudes. Barometer also senses the change in air pressure at a much higher sensitivity.

Barometer measures air pressure. Now why do we need to measure the air pressure? The answer is simple, to help the quadcopter determine the height it is at. We all know as we move to higher altitudes, the air pressure decreases. So the barometer will know the air pressure and help in determining the relative height and help us in providing Althold i.e Altitude hold. 

P = h⍴g 

HOW DOES A BAROMETER WORK? (15 mins) 

These pressure sensors work on the principle of mechanical bending of silicon diaphragm by gas pressure. 

Mems barometer(pressure sensor)

The pressure in the cavity is taken as reference pressure. If the pressure outside increases more than reference pressure, the diaphragm bends inwards and when the pressure outside decreases as compared to the reference pressure, the diaphragm bends outwards. One way to convert the bending of diaphragm to a corresponding electronic output signals is the capacitive way. The bending of diaphragm in turn changes the distance between two metallic plates which affects the capacitance. We know that, 

C = εA/d 

Thus any change in distance (d) between the metallic plates changes the capacitance. Using these values the system calculates the pressure changes happening in the surroundings. 

OPEN SESAME EXPERIMENT (PLUTO BLOCKS) (15 mins) 

This experiment very well demonstrates the working of barometer sensor. Trainer can demonstrate it to students.

Instead of using the take off button on the Pluto Controller App, you can use the Barometer sensor present on the Primus V4/ Primus X board to take off. Just blow some air on the drone and it will take off! 

The barometer sensor measures the pressure in the air. If you blow air over it, the sensor senses it and for that instant, the pressure reading changes. This moment can be used to command the drone to take off. Remember to arm the drone from the app before running the project.

Keep the drone near a door and open/close the door at a fast speed to make the drone takeoff!