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Liberty Common High School Electronics and Robotics

Introduction

CONCLUSIONS

Materials

Egg Drop Experiment Design Process

Arduino Accelerometers

This program is based upon collaborative work supported by a National Science Foundation Grant No. 0841259; Colorado State University, Thomas Chen, Principal Investigator, Michael A. de Miranda and Stuart Tobet Co-Principal Investigators. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Josh, Cody, Tim, Nate, Matthew, Troy, and Rob

During this project we learned how to program an accelerometer to measure acceleration using an Arduino microprocessor board. The coding for this project consisted of a number of mathematical equations and statements of variables that helped produce accurate results. The documentation for the accelerometer also turned out to be key. Students in other classes had difficulty using the accelerometers, and it was necessary to better explain how they worked.

While the project was a success, there were several things which could have been done differently. The other classes were never completely satisfied with how the data from the accelerometer was displayed on the computer. Also, the other classes were interested in measuring acceleration in multiple directions, so a multi-axis accelerometer would have been a better choice.

Arduino Uno SMD• The Arduino Uno is an easily

programmable microcontroller board, perfect for small electronics projects.

• The Arduino detects the voltage generated by the accelerometer and calculates the acceleration is g’s.

Acceleration is extremely important when designing safety equipment. For instance, the main function of a bicycle helmet is to limit the acceleration of a persons head when it hits the ground. Since acceleration is important for safety, it is also important to measure it accurately. The goal of this project was to create an accurate accelerometer which other classes at Liberty Common High School could use for measurements. The accelerometer designed in this project was used successfully to test automobile crumple zones in the Mechanical Engineering class, and helmets in the Bio Engineering class.

The accelerometer was constructed using an Arduino Uno microprocessor board and a Freescale Semiconductor accelerometer chip. The project involved physical assembly, computer programming, testing and design revision.

Freescale Semiconductor MMA2301KEG• The MMA2301KEG is a single axis

accelerometer with a range of +-200g• The accelerometer produces an

analog voltage proportional to the acceleration that is measured.

Laptop Computer• A computer is needed to write the

software that the Arduino runs. • Data collected by the Arduino is

transferred to the computer where it can be displayed on the monitor.

Question: How many G’s can an egg withstand before breaking?

Egg #1

Height (cm)Acceleration (g's)

Trial 1 Trial 2 Trial 35 14 18 15

10 34 114 8415 150 111 10020 156 134 170

Egg #2

Height (cm) Acceleration (g's)Trial 1 Trial 2 Trial 3

5 54 25 4910 78 66 8215 160 135 19820 198 198 14025 82 198 N/A

The egg and accelerometer enclosed in a plastic cup for testing.

Arduino with accelerometer attached

***Red data indicated the point at which the egg cracked***

Test Results

Assembly-How long should the wires be?-How can solder joints be reinforced?

Programming and Documentation-How does voltage translate to g’s?-What should the sampling rate be? -What type of instructions are needed so the other classes can use the accelerometer?

Testing-Did the code function properly?-Did any connections or components break?-Was the accelerometer easy to use?

Modifications and Improvements-What features did the other classes like?-What can be changed to make the accelerometer easier to use?

Testing Procedure1) Secure the egg and accelerometer to the plastic cup, enclose the cup in a sealable

bag.2) Connect the Arduino to the computer and begin collecting data.3) Drop the egg three times from 5cm and record the maximum acceleration measured

by the accelerometer each time.4) Increase the drop height by 5cm and drop the egg three more times, recording the

acceleration each time.5) Repeat step 4 until the egg breaks.

Purpose:Perform a simple egg drop experiment to test the functionality of the accelerometer and learn about how many g’s an everyday object such as an egg can withstand without damage.

Egg Drop Conclusions:The amount of acceleration an egg can withstand without breaking is amazing! However, for this particular experiment the accelerometer might not have been accurate enough. The reading varied greatly even when the egg was dropped from the same height, so it is difficult to determine if the accelerometer was producing valid data.Picture Souces:

1) http://arduino.cc/en/uploads/Main/ArduinoUnoSmd.jpg2) http://laptoppics.com/laptop/hp-probook-6360b-pics-prices/

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