I rapidly prototyped a dorm room motion detector. This product aims to help people who have random roommates, where these roommates persistently enter private spaces without permission.  This device can be used in any individual personal spaces of a shared dorm room. 

Duration: 1 Week

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The aim is for the sensor to be represented as an object that just blends in with the dorm room environment, for example a trail-mix box on a desk. This is a really fun and cool design decision. The goal is to scare the roommate by catching him or her off guard. The hope is that the invader never determines what object the sensor is hidden in, given that this object can constantly be changed by the owner.

Materials Used:

I used an Arduino Red Board, Arduino Ethernet Shield Board, Ethernet Cord, a Piezo Buzzer, Jumper Wires, my cellular device, and a LED to build my prototype.



The users of this alarm system will be geared towards college students who have random or untrusted roommates, where the user has a personal area that no one else should enter outside of the user’s presence. The task is to protect users’ privacy and expel all worries that come along with having a new and random roommate. The system will alert the user through text message when someone has entered the restricted space. For this design, I am assuming users between the ages of 17 and 25 (undergraduate and graduate school ages), the user has a mobile phone with unlimited text messaging or an email address that they check regularly, the user has a roommate, the user has a personal spot that should not be invaded after they leave the room or apartment.




How It Works:

The owner of the motion detector will plug it in as he or she leaves the room. The system takes about two minutes to calibrate the room for infrared light, using the passive infrared sensor (PIR sensor). Anything above the levels calibrated will set off the motion detector from as far as 20 ft., given that more heat is present from someone entering the room After the system has been calibrated the owner receives a text saying that the sensor is active. When motion is detected, the sensor piezo buzzer sounds off and a text message indicating that movement has been sense is sent to the user's mobile device. The owner also receives a text messages with recorded times for when motion begins and another when motion ends.


The Process:

In terms of the process that I went through to create this sensor, I wanted it to be something small so that it can easily be moved to different areas of the room. For example, it can be put in your personal closet, desk space, bathroom, pantry, or where ever else the owner desires. I made this decision for the design to be small, simple, and movable because based on many “freshman year of college with random roommate” stories, different students had different areas that they wanted to reserve for themselves and would be frustrated after finding out their roommate entered those areas to take items without permission.

  1. This the PIR sensor that I used. 
  2. I attached wired to the PIR sensor and added wire extensions to provide more flexibility while building.
  3. I added an a LED an resistor to test the PIR sensor. The LED flashes when motion is detected.
  4. I added the Piezo speaker for alarm. Alarm sounds and LED flashes when motion is detected.
  5. I added the Ethernet Board.
  6. Transferred wires from Arduino Red board to the Ethernet Board and coded for text messaging.

Please view the video above for more details.

Usability Criteria:

I wanted to sensor to be easy to learn and easy to use. Due to that fact, I have hidden the complexity of the system, users will simply plug in the sensor and receive text messages like they normally do.

What Is Next? 

The design is currently just working from my desk. In terms of the robustness, I have designed the prototype to be placed into a small hard plastic object. The hard plastic case will work as an encasement. Users can then stuff it in socks in their draws, drop in on their bed, put it on a cereal box on their desk, put it in the corner of their closet or where ever else they may please. The material that I want to buy for this is the durable plastic that is used for storage containers, allowing the users to put the sensor anywhere without worry. Given that this prototype is powered by software, the question on error recover may come up. From the test that I have ran, the sensor is not at all faulty once it is calibrated correctly. In the case of any error, I would like to incorporate a hard reset button on the clear plastic shell that the device will sit in.

On question of reentry after the alarm has been set, just like modern day home alarm system, the user will simply have to turn the alarm off (plugging it out based on the current prototype). Another feature that I would like to add in order to make cases like this more usable is adding a text back feature. For example, when the user receives a text saying that the sensor has been activated, in the case that the user would like to turn it off, he or she would be able to send a text such as “TURN OFF” to disable the system. I would also like to add an Arduino board that uses WiFi capability, instead of using one that uses the Ethernet cord in order to allow for more mobility. With a future version of this system, more mobility (the case), portability (wifi), and usability (texting back) would definitely be included.