Throughout the process of creating my project, which is a pulley-system sound generator, I was able to learn many things through trial and error. My project wishes to show the energy conversion process of light energy then to sound energy. It displays this through a device meant to educate children that is complete with a pulley system, solar panels, electric motor, and drum.
Along the way, I had to consider many things while creating my work, such as: “Would this be suitable for my customer (as in usefulness, durability, attractiveness)? Would this work? How can I make this show energy conversion more clearly?”. By asking these questions, I realized many slight errors in my sketch, and changed a few things. I also created several prototypes for each section of my project and assembled them together in the end using tape at first, then hot glue. Other than making prototypes and refining them, I also tested using established criteria, and optimized my design from feedback of users.
Shell and device container:
On the first day for creating this project, I first started working on the shell of my pulley-system sound generator; it was made of double-layered cardboard strips glued together to stabilize the device as the motor rotates. Since one of the criteria that I first identified at the beginning of this project was to have a durable toy for children, I wanted to make sure that the shell containing everything was durable and steady.
My main goal while building was to make sure everything was most suitable for my solar panels as well as my electric motor (as the shell contains them), so that the energy conversion process is more apparent in this device. As I worked on the board that the solar panels would be attached to, I realized, however, that the electrical wires of the panels would not be able to connect the boards and the motor since the cardboard had no hole in it. I ended up cutting two circles, each with a diameter of 2.5 centimeters, off the cardboard.
I also realized that the angle of the solar-panel-attached cardboard (40 degrees) was too small to receive the most amount of sunlight. This would weaken how observable the conversion process is, so I ended up changing the angle to 55 degrees after I did some research for my calculations (it turns out that the optimum tilt for a solar panel is its location’s latitude; it also depends on season, so if it’s in the winter, another 15 degrees should be added. This is why my solar panel angle is 55 degrees, since Beijing’s latitude is around 40 degrees).
(The little triangles, as shown in the picture above, are to make sure that the cardboard is 55 degrees. I changed their degree after the first prototype)
Electric motor and solar panel system:
I worked on the complicated system of the solar panels and the motor for the next few days. This one took a lot of time and revisions to complete because we had to figure out how to make sure that the electric motor receives enough energy to rotate. I started with my first prototype: with one solar panel to test out how the motor fits best with the solar panel, and how well the motor would work with a handle attached to it while only wired to one solar panel.
One of the first challenges I ran into was which type of DC motor would fit the electric panel best. I ended up with a small-sized DC motor after testing several motors one by one with my single solar panel. Under direct sunlight, the motor rotated well and successfully.
Here is a video of it (press link): singlesolarpanel
However, even though the handle seemed to work well, it would occasionally become “stuck” on the rotating rod of the electric generator and stop spinning. My conclusion was that the electricity produced by one solar panel was not enough to power the motor to rotate the rod. This means my model sketch was right, and I would probably need to have two solar panels in order to power my project. This was my second prototype for the solar panels.
After consulting teachers and the internet, I decided that I would connect the two solar panels to my motor with a series circuit instead of a parallel circuit. This means that one electrical current would run through the whole system in one path (unlike a parallel circuit, where there are multiple paths) and there would be an increased amount of voltage sent to the DC motor compared to one solar panel. This means that the motor would rotate faster than before and have a larger possibility of turning the handle smoothly.
I used many websites as reference to help me find how to connect two solar panels together (and also if I should use a series circuit) in order to provide me with twice the amount of energy:
MLA Citation: Punyani, Veenu. “How to Wire Solar Panels in Parallel or Series.” HES PV, HES PV, 29 Oct. 2014, hespv.ca/blog/wire-solar-panels-parallel-vs-series/.
MLA Citation:“Connecting Solar Panels Together For Increased Power.” Alternative Energy Tutorials, Alternative Energy Tutorials, www.alternative-energy-tutorials.com/energy-articles/connecting-solar-panels-together.html.
We first connected the electrical wires of the solar panels to their negative and positive terminals using electrical tape, so we can still easily remove the wires if we made a mistake (this was the second prototype for the electric solar panels):
It successfully worked, and the handle spun more smoothly on the electric generator than before. To make sure that the system would work more well within my device, where the motor would also be burdened by the pulley system, I cut off the extra parts on the handle, so it would become lighter in weight.
One of the criteria that I identified at the start of the project was to consider environmental impact. I tested the solar panel and motor a few more times to make sure that the motion would be fluid under direct sunlight, with the handle at the same place on the rod each time; it was indeed able to do that, so it means that my project considers environmental impact through using a renewable energy source to power it.
As my final and third prototype for the solar panel system, I soldered all the terminals together, and attached the solar panel system to my device container using velcro tape.
Here is a video of it on my device with the pulley (sunlight replaced by LED light): Movie on 1-18-19 at 3.05 PM
Pulley system and drum (vertical boards, pulley, string and drum):
As the final part of my device, I mostly worked on the pulley system and drum of my project. This is the section that will mainly be the part of my device that transfers the light energy and electrical energy to mechanical energy and sound energy. I didn’t really do specific prototypes for this system because of time constraints, but I modified it throughout the process.
As I constructed the pulley system, I mostly just followed my model sketch. However, I refined this section of the product along the way so that it would burden the electric motor of the device less. For instance, instead of just using a wooden dowel to be inside the pulley wheel, I used a dowel encircled by a plastic straw to decrease the amount of friction between the pulley and stick. Additionally, I used a thinner, wool string (the “cable” of the pulley system) so the electric DC motor would use less effort as it pulls. Another thing that I did was add stoppers made of bendy pipe cleaners beside each end of the pulley wheel to keep the wheel from sliding back and forth across the dowel.
For the pulley system’s load, I had changed it from a rubber ball to a big bolt nut, something lighter than before. The nut perfectly balanced the system because it wasn’t too light so that it was just pulled towards the pulley and it wasn’t too heavy so that the motor wouldn’t be able to move.
As for the two vertical wooden boards that are part of the device, I made them much shorter than the planned design because I felt like it would strain the motor again if it had to pull the load with an extra distance and height. Because of this, it was no longer needed to create a cardboard shelf for the drum or else the drum would be too tall.
On the other hand, for the drum, I constructed it using a cut balloon and a recycled soup tin-can. I wanted to use materials that considered environmental impact, so I found this tin-can at home to add to that. When I attached the drum to my device, I used duct tape instead of hot glue, because the hot glue would cause the pressure inside of the metal tin-can to build and explode.
Mostly for what I’ve done while designing the pulley system of this device, is to make sure that the electric motor can coordinate well with my system. By doing so, I can create a better experience for my clients (children) when they can see an obvious process of energy conversion within my design. Basically, this can help me to reach my main goal of educating children about energy conversion.
Here are photos of what the complete device looks like from behind after I attached the pulley system to the rest of the design (so you can see the pulley system more clearly):
Attached below is a revised sketch of my original model based on the changes I made throughout my designing process:
When I finally tested the first prototype of the device (the photo of this is the one above the sketch) it was able to meet a few of my previous criteria. The cardboard container was durable and steady as the motor rotated, I was able to use a renewable energy source to power the motor, and several materials (tin can, solar panels) that were consisted of this project considered environmental impact. It was pretty aesthetically pleasing and not too crudely designed as I measured before I cut all my materials.
However, the only thing wrong was that pulley system wasn’t able to move as expected. I was testing this using my criteria of whether this device would work and show energy conversion. It did not work and the motor did not move at all; one of the problems that the device faced was that the motor did not have enough power to pull the load of the pulley system.
Here is a video of the device under LED light: Movie on 1-18-19 at 3.25 PM #2
(From this video, you can guess the energy conversion process my device shows, which is light energy to sound energy. The device collects light energy from its solar panels and converts it to electrical energy through the motor. It then transfers the energy to the pulley system as mechanical energy, then uses gravitational energy of the load of the pulley system to create sound energy from the drum of my device)
Even though I tried to lift some burden on the electric motor before by changing other parts of my design, I decided that the problem was the motor and the solar panels itself. The solar energy received from the two solar panels was not enough to power my whole device, and this caused the motor’s rotating strength to be weaker than what the pulley system needed in order to pull the load.
What also suggested this was the feedback gathered from a user (Annie) of my toy: “This project is very creative, but one way this pulley system sound generator can improve is that the metal bit (bolt nut) can bounce on the drum with smoother movements. However, I believe that this can be done if the solar energy received from the solar panels can increase.”
My solution for this problem would be to wire another solar panel along with the initial two (attached using velcro), it would just be another addition to the established series circuit and I would lengthen the cardboard the solar panels are attached to to give it space. If I added this extra solar panel, it would contribute more solar power for my motor and give it a stronger spin.
I would probably need longer wires to connect the two far-ended solar panels on each side to the terminals of the DC motor though.
Here is a plan for the solution that I drew:
In spite of this, I did not have enough time to operate my plan for a second prototype of the device, so I was forced to complete this project with only two solar panels.
In conclusion, regarding the creation of my project, I followed the process of creating prototypes, testing the prototypes using criteria, gathering feedbacks from users. Then using the test results and feedback, I made a plan to optimize my design even though I did not have time to actually complete the solution. I felt like I learned a lot because of this project, and the experience was rewarding!