Dormostat

Inspiration

Three college houses at Penn - Kings Court English, Du Bois, and Gregory - do not have cooling systems, causing students to have to work and live in sweltering conditions. In the winter at New College House, where Div and Landon reside, our rooms are constantly kept at 75 degrees Fahrenheit, and residents are complaining about it being too hot. Though, when we sleep with our windows open, we find ourselves waking up in the middle of the night because our rooms are too cold.

What does your project do?

Dormostat aims at being a cost-effective, automated and user-friendly temperature regulation device for student dorms with deficits of any form of climate control. It uses the natural cooling processes in the ambient environment, and interacts with them by acting on the dorm room window and adjusting it based on the user specified conditions.

How you built the project & technical specs

To construct Dormostat, we spent our first week designing the circuitry and code. This presented quite a few challenges, especially with our Bluetooth modules not working as we expected it to, and our Servo motor malfunctioning at times. Once these challenges were overcome, we focused on creating an actual window for demonstration purposes. We first designed the window in Solidworks and converted it into a DWG to be laser cut. Once these were cut, we applied a hinge between the glass and the frame and bolted it down. This was where we decided to use a spring to keep the window in a naturally closed state. We also designed an arm system with three components to be 3-D printed, but since the 3-D printers were constantly in use during this busy week, we settled for laser cutting an arm and taping it to our motor.

The 8.5”/11” self laser-cut window used for demo purposes has a rotatory opening-closing mechanism. The window uses a spring connecting the frame to the acrylic inside so as to keep the window permanently closed (or tending to close). The servo rotates through an angle determined by the magnitude of the temperature delta, and the direction determined by the positive/negative sign of delta. When the delta is positive, the arm turns clockwise, pushes the window outwards, and fixes in position, enlarging the window opening. During counter -clockwise motion, the arms retracts from the acrylic, creating space for the spring to pull the window inwards, reducing the opening.

Design iterations

While we kept the same initial design for our code and circuitry, we went through a few design iterations for our window and motor-arm system. We originally were going to 3-D print a motor arm to affix to our motor, but because of the lack of printer availability, settled for creating an arm to be laser cut and attaching it to the motor wheel. The designs for our original motor arm are included in the attached ZIP file.

What parts did you use?

Dormostat uses an DHT11 Temperature & Humidity Sensor, HC-05 Master/Slave Bluetooth Module, LCD Backpack, Parallax Motor, Arduino Uno, Arduino Wifi, three buttons, and an LED.

How does everything work together?

On the user interface module, the LCD backpack displays the current temperature and humidity readings of the of the room. Using the buttons on our product, a user can input the desired temperature from 60 - 80°F, in increments of 0.5°F. The difference between the desired and actual conditions of the room is then transmitted over bluetooth to our motor module. Every 5 minutes, depending on the significance of this delta value, the motor will adjust the window opening accordingly, providing the user’s desired temperature in the room.

Challenges and issues you ran into, how you overcame them

The code behind Dormostat proved to be the biggest challenge. The first challenge was transmitting the temperature delta between the interface and the motor module. Since Bluetooth can only translate one character at a time, we had to first translate the delta values into single characters on the motor module itself, creating character arrays to translate back the values compatible with our temperature algorithms. Additionally, we devoted time to determining the most efficient way to filter our temperate sensor data. This was then done by taking select values over the sensor readings of the past 30 seconds and then designing a low pass filter that allowed our readings to be less volatile. The other major challenge was translating the motor motion to the window, and after attempts to move the window by mounting it on the motor, and else-wise, having the arm push and pull the window, we decided to rig a spring to pull the window inwards (close it) no matter what. The only adjustments would then be by pushing it. However, while the idea worked in practice, our final challenge was power deficit in the motor module, due to which the rotating arm was unable to move the actual window prototype.

Additional Features

One interesting feature we chose to include in the product is night mode, that allows the user to reduce how often the motor moves. Instead of the usual 5 minute interval, the night mode changes temperature adjustment to every 60 minutes, indicated by a green LED within the circuit.

What you learned

We both didn't have much experience with circuity and arduino coding before this semester, so this project served as a great opportunity to learn these skills without much direction. Additionally, we made numerous trips to the RPL to change the design of our window (changing bolt hole locations, increasing the spring tension, etc.), so we had to learn quickly how to make precise cuts on an already constructed product. Lastly, this project presented us many situations where we had to change our design plans, so being flexible, while keeping our end goals in mind is something this project taught us.

What’s next for the project

Moving forward, we have many ideas on how to improve Dormostat. Instead of using a motor arm, we want to use an actual linear actuator to translate the rotatory motion of motor to move a real up and down window. We also would like to test it in our market, including dorms at Penn devoid of air conditioning: DuBois, Gregory, and King’s Court English. Since a spring mechanism is impractical for actual rotating windows, we would focus on creating an arm that moves in two dimensions at a joint, instead of just one. Dormostat would also include humidity regulation, and we would account for four scenarios - hot and humid, hot and dry, cold and humid, and cold and dry. This would influence how the arm moves so as to bring both the conditions within a suitable tolerance of the user-specified values. This would account for a broader range of possible ambient conditions, such as rain, fog, and snow.