The aim of this project was to design and create what’s known as an “Interaction Folly”, which is a fundamentally useless object that provides an interaction with a user or the environment in an illogical or counter intuitive way. As they lack a real function, they are often created for entertainment as a practical joke product. This was carried out in teams of two, with fellow student; Andrew Taylor being my partner.
Initially, the concepts we generated were indeed follies, as they didn’t have a useful function, but they lacked the interaction aspect that was key to the project. One of these was a shelf that would tilt under the weight of any object placed on it, meaning that it would immediately fall off. While it was both useless and illogical, an object falling straight off wasn’t really a true interaction and was more of a dysfunctional product. Instead, we then developed the idea of a safe that would only allow the door to be locked if there was no object inside it. Of course, this meant that valuables would be no more secure inside it than they would outside. The interaction was based around an electronic sensor, such as a strain gauge, inside that would detect the weight of an object placed on its floor. Then, through the use of a solenoid or servo motor, it would move the position of the lock so that a key can’t be inserted to lock it.
After realising the potential of an electronic interaction system, we then researched thermistors and how a folly could interact with a change in temperature of the environment. A thermistor is a type of resistor where the resistance is changed greatly with a change in temperature. As a fan is usually designed to counteract a high temperature by blowing air on something to cool it, it was an obvious starting point to develop the folly from by reversing the logic so that it worked in a counter intuitive way. The “Annoying Fan”, as I named it, was designed to blow air when the temperature is already low, making the user feel even colder and then stop blowing air when the temperature increased to a set point or more so that the user would become too hot. I created a cartoon style storyboard to explain how the fan was designed to work, showing the effect that the environment’s temperature had on the fan and how this then affected the user. Rather than showing it as a series of frames, I made it into a simple flow chart which was more effective at conveying the bipolar nature of the fan.
We then built a circuit that made use of a thermistor, a transistor and a relay to control the switching on and off of the fan. The mechanism of which, is explained in the annotated circuit diagram that I posted previously. A problem we had with getting it to work as predicted was that the current flowing into the base was insufficient to saturate the transistor and so it wasn’t working as a switch to energise the relay. This meant that the fan remained running even if the temperature exceeded the set value. This problem was caused by the resistance of the circuit being too low, even when the thermistor had reached its maximum and the variable resistor was set all the way to the top. I solved this by adding another resistor to the circuit which caused the voltage to reach 0.7V at the base when the temperature exceeded the set value.
I then tested the circuit using a soldering iron to heat the thermistor above the set point. Connecting two voltmeters, one to the base and one to the collector (which is also the relay coil) connections of the transistor, I monitored the voltage of each. At room temperature, the base voltage was 0.5V and the collector voltage was 7.19V. As shown in the video, the increase in resistance in the thermistor caused the base voltage and base current to increase. This increase in base current caused the transistor to start to conduct between collector and emitter, and the voltage on the collector started to fall towards the emitter voltage, i.e. 0V. As the base current increased further, the transistor became saturated and at this point, the base-emitter voltage did not increase above 0.714V. The collector voltage is almost the same as the emitter (0.13V in the video). 9V from the battery minus the 4V across the resistor meant that there was then 5V across the relay coil, causing it to switch off. This is heard as a clicking sound in the video. The fan then stopped blowing.
When the heat source was removed, the resistance of the thermistor decreased, causing the reverse process to occur.
Overall, I would say that the practical side to this project was very successful as we created and tested a working prototype of our concept which worked exactly in the way we had designed it to. The video clearly demonstrates the way in which the interaction occurs. It could be improved, however, by using a bigger fan, which would make the blowing action more obvious as well as manufacturing a professional looking housing to make the prototype more like a real, finished product. The video could be improved by filming a staged scenario of someone using the fan, rather than just a laboratory test.
While the concepts we generated were imaginative yet practical, I think that further exploration and development would have helped to make a better product that would have been easier to create and would have been more effective visually. A wider range of ideas to choose from as well as undertaking more research into electrical components, other than thermistors, could have meant that the folly was more technologically advanced and so was more entertaining and impressive for the user/ audience.
No comments:
Post a Comment