Temperature Controlled Box – Final Build

The final build of our project was successful in creating a +7 degrees Fahrenheit change in less than 1 minute, and a -7 degrees Fahrenheit change in less than 3 minutes. We could have pushed our system further, although we found this temperature range to be fitting of realistic temperature settings in traditional HVAC systems. In any case, the project fulfilled its designed purpose.

 

Despite the project being a success, there were a few issues and design changes which we did not implement but would have improved the overall functionality of the system. Once obtaining a desired temperature, the system would not rerun a heat or cold mode until the actual temperature dropped below or rose above 2 degrees of the ideal (assuming the ideal temperature had remained constant). This was so the fan or hair dryer would not be turning rapidly off and on. When the room reached a sub 72 temperature, the fan would not reactivate for some time, however the hair dryer would never last more than 10 seconds. This is likely due to the moderate insulation of the control room, which could have been improved by sealing off gaps more tightly and adding a layer or two of higher insulating material.

 

Another minor issue we had was the npn transistor eating a small about of voltage when passing VCC, which decreased the overall speed of the fan. We considered using a different transistor to see if it consumed less voltage, but the cooling process operated in a reasonable amount of time so we decided to leave it. This would be an ideal fix, however, if a smaller cooling time is desired. It is also important to note there may have been some current loss due to the potentiometer also being connected to VCC in parallel, so it may have been a good idea to throw on a resistor in series and recalibrate the potentiometer values to fit the new, probably smaller, voltage range.

 

Despite these minor setbacks, the project turned out almost better than expected. The enclosures were well constructed, everything fit together nicely, and we even had a laser engraved decal [done at First Build] on the front and top of the control room, with our names and the project logo. Overall, we were able to successfully build our designed project, and every team member did their share of work towards the final completion.

Lucky Debonair – Temperature Controller – Big Picture

Every day, millions of people around the world use indoor temperature controls in the form of air conditioners and heaters. Additionally, some computing machinery and medical supplies must be stored at specific temperatures to remain optimal. To get an idea of how these systems function, we decided to build a small environment and attempt to keep it at a certain temperature.

Our temperature-controlled environment is a box roughly 200 cubic inches in size, and is made of poplar wood. On each side of the box is an opening, one for a hair dryer and one for a small fan. The fan draws air into the enclosure from a separate wooden box of similar size that contains a series of ice packs. Inside of the enclosure is an A3BU micro controller, which has a built-in temperature sensor, as well as a breadboard with an exposed LED and other necessary wiring. The hair dryer is plugged in to an “off” outlet of a controllable power relay that can be manipulated by the code on our A3BU. The fan receives its power directly from VCC of the A3BU.

The code that is loaded onto the A3BU controls which outlet on the power relay is activated. If the temperature in the enclosure is warmer than desired, the fan is activated and cold air blows in. If the temperature is cooler than desired, the off outlet relay is switched on, and the hair dryer is activated. Otherwise, if the temperature is as desired, both outlets are turned off. This keeps the control room at a relatively consistent temperature. By doing this project, we gained a basic understanding of the temperature-controlled systems found around the world.