Fridge Door-closing Reminder | DFRobot Science Lab Season 2 EP09
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AshG Mar 02.2021

DFRobot Science Lab Season 2 

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EP09: Fridge Door-closing Reminder

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Introduction
 

Standards

NGSS

4-PS3-2 Make observations to provide that energy can be transferred from one place to another via sound, light, heat and current.

4-PS3-4 Use scientific concepts to design, test, and improve equipment that can transform energy from one form to another.

Science - Grade 3-5

Overview

In these busy times it is now common to forget to close the fridge door. This lesson will lead students to explore how to make a fridge door-closing reminder, and determine the proper height the temperature sensor should be positioned at based on the principle of hot air rising and cold air falling.

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According to the NGSS standard engineering design requirement in 3-5 grades, the course is divided into 3 parts, they are respectively “DEFINE ENGINEERING PROBLEMS, DEVELOPING POSSIBLE SOLUTIONS, OPTIMIZING THE DESIGN SOLUTION”. Just like engineers, students will find problems, set goals, design plans, build and test models, optimize and improve models, and finally complete the engineering design task.

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Materials

Play and Learn with Boson Science Design Kit: https://www.dfrobot.com/product-2176.html

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Activity 1 DEFINE ENGINEERING PROBLEMS

Find Problem

In the hot summer, when we open the refrigerator and take out the delicious ice cream, we leave with the door open. After a while, when we come to the refrigerator again, we will find the delicious ice cream melted. Oh, what a terrible experience!

Why not make a refrigerator door-closing reminder? This is a good idea, let’s do it!

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Engineering Goals

Make a refrigerator door-closing reminder.

Activity 2 DEVELOPING POSSIBLE SOLUTIONS

After determining the engineering goals, let us follow the process of “Brainstorming-Drawing Prototype Diagram-What You Need-What You Do-Test and Evaluate”to complete the making of the refrigerator door -closing reminder.

Brainstorm

Let’s first brainstorm how to build a refrigerator-closing reminder. In the process, try drawing a prototype of the reminder.

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Draw Prototype Diagram

Through brainstorming, we have initially understood the function and structure of the refrigerator door-closing reminder. Try drawing a prototype diagram. In the production process, the prototype diagram will be an important reference.

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What You Need

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What You Do

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Test and evaluate

After the above steps, a simple refrigerator door-closing reminder is completed! Now try it to test its performance.

When fixing the temperature sensor, will the experiment result be different when the sensor is placed at different heights? Which height will give the best result? Try proposing an optimization plan to improve the response speed of the reminder. 

Activity 3 OPTIMIZING THE DESIGN SOLUTION

Let us continue the process of “Brainstorming-Drawing Prototype Diagram -What You Need-What You Do-Test and Evaluate” to carry out optimization and iteration of fridge door-closing reminder.

Brainstorm

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What You Do

Through brainstorming, we guessed that after opening the refrigerator door, the temperature changes at different heights of the refrigerator. Fixing the temperature sensor at the height with the fastest temperature change can increase the response speed of the reminder. Is it true? Let's verify it together!

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The table of the response time of the reminder:

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Note: In the actual experiment, you can allow 3 groups of students to conduct experiments at different positions of the refrigerator door at the same time, and finally gather the data together to save experiment time.

Test and evaluate

The referable data is as follows:

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Through 3 sets of comparative experiments, we can conclude that the temperature at the bottom of the refrigerator changes fastest, which is the best position to fix the temperature sensor.

What happened?

In the hot summer, the air temperature in the refrigerator is low, and the air temperature in the environment is high. When we open the refrigerator door, due to the temperature difference, the cold air and the hot air will transfer heat through heat convection. So, the air near the refrigerator door will cool down.

Just like a hot air balloon will rise, near the refrigerator, the hot air will rise and the cold air will drop, so the lower part near the refrigerator will be colder.

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Further Exploration

In this activity, we made a very simple refrigerator door -closing reminder, but it can only be used in summer. Think about it, if in winter, is there a better solution? Let’s continue to explore it!

Science Background

Why do hot air rise and cold air fall?

Air is made up of many invisible molecules.

In hot air, the molecules move fast and collide with each other, increasing the space around them, so the hot air will expand. After expansion, there are fewer molecules and lighter weight per unit volume, so the hot air will rise.

In cold air, the molecules move slow, and there are more molecules and heavier weight per unit volume, so the cold air will drop.

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Hot air balloon and Kongming lantern

Hot air balloons in Turkey and Kongming lanterns in China both use the principle of hot air rising.

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Conclusion

In this project, we made a refrigerator door-closing reminder, and optimized the design of the reminder by using the knowledge of hot air rising and cold air falling.

The project is going to an end, please remove cables, and put all the BOSON modules back into the original positions of the kit.

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