24/05/18 giovanni 0 0
![](http://opentp.fr/en/app/wp-content/themes/darfuino/includes/pics/logo-opentp-2.jpg)
A Geiger counter simulator
Developed by Margaux Khalil (École Estienne), Julien Bobroff and Frédéric Bouquet (Laboratoire de Physique des solides, Université Paris-Sud and CNRS). More information and other projects on opentp.fr/en
![](http://opentp.fr/en/app/wp-content/themes/darfuino/includes/pics/pictos_pitch.jpg)
Level : Medium
1 day
Build a device that emulates the behaviour of a Geiger counter exposed to a radioactive source
![](http://opentp.fr/en/app/wp-content/uploads/2018/02/openTP_principles_quantique.png)
The physic in action
Radioactivity consists in the emission of particles from substances. In certain cases the emitted particles are electrically charged and can trigger a Geiger counter.
The counter reacts producing a small spark inside it that can be “heard” as a characteristic “click”
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Arduino
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Ultrasonic sensor HC-SR04
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relay module
Material
![](http://opentp.fr/en/app/wp-content/uploads/2018/01/openTP_student1_brico4.jpg)
Step 1
Connect the relay module and the ultrasonic sensor to Arduino.
There is plenty of tutorials about how to use an ultrasonic sensor and a relay module.
![](http://opentp.fr/en/app/wp-content/uploads/2018/01/openTP_student2_programme1.jpg)
Step 2
Write a program that measures the distance \( d \) of an object and trigger the relay with a probability proportional to \( \frac{1}{d^2} \).
![](http://opentp.fr/en/app/wp-content/uploads/2018/01/openTP_student3_bricolage_papier1.jpg)
Step 3
Hide everything inside a tube with two holes for the speaker and the microphone of the ultrasonic sensor.
![](http://opentp.fr/en/app/wp-content/uploads/2018/01/openTP_student3_mesure3.jpg)
Measure
Approach an object to the tube pretending it is radioactive. The relay starts clicking and the frequency of clicks increases when the distance decreases. Make it realistic applying a radioactive sign on the object.
![](http://opentp.fr/en/app/wp-content/uploads/2018/01/openTP_student2_programme2.jpg)
Improve it
Substances with short lifetime emits particles with a rate exponentially decreasing with time. Can you modify your software such that you can simulate that?
![](http://opentp.fr/en/app/wp-content/themes/darfuino/includes/pics/question_3.png)
How do you characterise the substance in the latter case? Which numbers better describe the properties of the process you are observing?
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