1.0 Summary
Our design is that of a useless box, an idea Team Bryan 22201 haphazardly stumbled upon when researching new and exciting arduino powered machines, per request of Professor Sullivan. Team Bryan was originally enticed by the infamous ‘inebriator,’ however we were eventually won over by the ‘useless box,’ a project we felt would be manageable for the amount of time we had to complete both design and construction of said box. The purpose of the useless box is a machine that when manually switched on, will switch itself off. To first learn the habits of the box, we studied many videos from many different creators, all with a different take on how the box should be constructed. With this vital information in hand, we were able to begin hashing out ideas and designs for our very own absolutely useless box. Our design includes a balsa wood jewelry box that we reconstructed into the outer shell for our machine, a push arm consisting of 4 links that we designed in Solidworks and 3D printed, as well as various switches that to this day we still have not perfected the use of. This box clearly appeals to the college crowd as well as to any engineer that enjoys playing with Solidworks and Arduinos. While Team Bryan’s useless box has not been perfected, we have greatly enjoyed the design and build process involved and hope to continue work on this box in the future.
2.0 Introduction
This report presents a design for a ‘useless box’. The purpose of the useless box is to create a machine with the sole objective being able to turn itself off. We utilized a prefabricated box for the base of our box and from there built on the notion of using a servo motor to fulfill our objective. Based on other useless boxes we determined that the primary method to turn off the box would be to design an apparatus that shoots a finger out from under the lid of the box to flip the switch back into the off position. The main objectives of our design from this point were to determine a method to move our servo motor the correct amount and determine the shape/size of our finger and switch.
In working with the servo motor it was easy to program it using our arduino boards to move it a certain amount when the switch is flipped then have it rotate back to its starting position. Based on this we decided that to make it easier we would move our axis of rotation as close as possible to the switch because we could then simply modify the design of the finger to adjust it into the correct position for the finger to flip the switch. As we were limited in our choice of switch we were forced to test our servo with a more general shape of a light switch which we eventually incorporated into our final design.
Designing the finger was a much harder part as the geometry of a finger that will disappear under the lid was difficult to figure out. Using a base model of the light switch in solidworks we were able to determine a width for our finger and from there a scale necessary for it to be on. By placing the servo motor as close as possible to the switch we were able to create a drawing of the switch and servo together in order to figure out the geometry based on minimum dimension seen in Figures 1 and 2.
Figure 1: Concept design of “Useless Box” with minimum required dimensions
Figure 2: Initial design of finger with different placements of servo and switch
Eventually realizing we couldn’t be sure of our choice in switch and the geometry of our parts we went to a design for our finger that allowed us to adjust its dimensions after being printed. By making four different sized finger joints we were able to adjust the geometry of our finger based on our final design for the box and our decision on which switch to use.
3.0 Analysis
Essentially the ‘useless box’ is a box comprising of a robotic arm powered by a small servo motor, which is activated by a toggle switch. When the switch is turned to the ‘on’ position, the arm is activated inside the box. In one motion, it then opens the box up, flips the switch back into the ‘off’ position, and finally retreats back into the box.
The first part of the design we looked for, which was crucial to the project working, was the box to hold the arm, motor, switch, and arduino; we needed a box made of out of very light wood so that the arm would be able to open it up while putting as little strain on the arm as possible. The decision to use balsa wood was made and thus a balsa wood jewelry box was purchased. The cover to the box was taken off and cut into two pieces of different lengths. They were then reattached to the box; the shorter piece is glued down, while the longer piece had the hinges moved so that it opens in a different direction.
The arm used in the design was 3D printed out of ABS plastic using four individual pieces. The hardest part about creating the arm was building it so that it would be able to open up the cover to the box, and then be able to extend far enough to flip the switch back without getting caught on the cover on the way back into the box.
For the motor that controls the arms motion, we incorporated the arduino’s micro servo motor into the box. Using the servo motor, the arm has about 70 degrees of rotation. This also affects the way that the arm is designed, because its ability to flip the switch with only 70 degrees of rotation depends completely on the angles of the bends in the arm.
The motor also affects the switch that needs to be used for the design. The servo motor has to be strong enough to open the box and then flip the switch. A switch with as little resistance and friction as possible is optimal, but not easy to come by. This leads into where most of the problems with the design came from.
The motor simply did not have the strength to flip the toggle switches we purchased for testing. We tested five different toggle switches, four light switches (three of which acted as a toggle switch, and one was a sliding switch), a knife switch, two rocker switches, and a switch taken from a video-game controller. After going through about a dozen different switches, none of which could be switched solely by the power of the motor channeled through the arm, I finally tried to open up and smooth down one of the switches so that it would have less friction acting on it, but still be able to do its job. We also looked into buying a stronger a stronger motor, but quickly found that there were none in our price range that would work well with our arduino board.
The switch that worked the best was one of the light switches; this was the switch that was smoothed down, and will be used for the final design. However, the design still isn’t perfect. We may have to use something different to make the arm out of.
4.0 Conclusion
The Useless box is exactly as it says, useless. The purpose of this box is solely for an entertainment purpose. Putting the whole box together in itself has few components and is rather simple, regardless of the fact that our group discovered that even though something appears easy it may not be as easy as initially thought. Creating a shape for the arm was difficult so there were many small pieces made that can be connected together for an appropriate arm that will hit the switch when the switch is pressed, as well as making sure the motor and arm were strong enough to flip the switch back. With the right materials the creation process could have gone smoother but overall getting the components for the box as well as the code and internal pieces was rather simple and easy to gather. As of now there is no complication with putting the box together but it has not been tested for completed functionality.
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