We went into week 4 with a couple goals in mind, primarily focused on machining and testing the ABS enclosures we ordered as well as dipping our toe into the UI/UX design of the touchscreen.
For the enclosure, we did initial machining tests with a manual mill to get a better understanding of cut dimensions and tolerances. As shown in the below images, we first worked towards developing a CAD model for what we want the enclosure to look like in terms of all the necessary cuts that need to be made for the electronic components. These were then used as reference during manual milling. During machining, the design team cut holes for the wires and buttons, and slots for the USB hub and touchscreen. We were unable to make cuts for the vents due to the small tool size necessary, however the plan is to possibly purchase a smaller tool to then use in the lab.
From a manufacturing standpoint, in terms of producing 30 units by the end of the quarter, the design team also started looking into outsourcing our machining, and getting a quote for 30-50 units of machined enclosures from our primary supplier, Polycase. This would involve finalizing our CAD models and also ensuring that our supplier is able to do the machining to the level of detail that we are striving for.
From a GUI (Graphical User Interface) perspective, we got the go from the EE team on being able to use the touchscreen for this iteration of the system. Thus, this week we spent time brainstorming required and desired functionalities of the touchscreen. In addition, the team also got an initial understanding of the graphical capabilities of the touchscreen and how to begin exploration into the online libraries that can help with this.
Printed Circuit Board (PCB) Sourcing Update
This week both the design team and the EE team ordered different components to start developing our new version of the solar energy system. We ordered an LCD touchscreen and researched ways to connect and operate the touchscreen without having to buy any other processing components that would significantly raise our cost. This option, as opposed to our previous LED array, seems to be a promising user interface that will be easier to understand and has the capability of being updated as the user’s energy needs increase.
Some concerns that we currently have are whether we can successfully implement the LCD touchscreen without increasing cost and complexity. A limitation we might have is that the LCD could take all of the available ports in the Arduino, which we need for the power regulation of the system. Once we receive the screen, we will be testing whether there are other alternatives to join the LCD to the Arduino without using all the ports. Another concern we have is the complexity we might be adding while changing our main manufacturing process. We worked with laser cutters during our last quarter, but now we are pivoting to mills and CNC machines, and this transition might take some time for us to adjust.
These changes will allow us to meet the revised technical requirements that we defined at the beginning of our journey with this project. Specifically, the following requirements:
User Requirement --- > Technical Requirement
For next week, we are planning on testing and working with all of these components that we bought, and confirming that we are going in the right direction using an LCD touchscreen and modifying an outsourced electronic enclosure.
The EE team ordering LCD touchscreens while the sun was setting
This past week, the design team consulted with Craig Milroy, the head of the Product Realization Lab. We communicated our design goals i.e.improving the enclosure design while minimizing unit cost to be able to quickly and efficiently produce thirty units for the summer. Craig recommended that we look into ordering online electronics enclosures that have already been manufactured and then post-machine them. This could be done using the manual mill or the CNC mill to create holes and cuts for wires, vents, screens, etc. We realized that we could use the manual mill for early prototyping, however the CNC would be optimal for manufacturability and precision. In addition, the CNC manufacturing could be easily outsourced once the design has been finalized.
He also recommended increasing out target goal of completed enclosures for the end of the quarter, for example from 30 units to 100 units, so as to further reduce the cost per unit by ordering the enclosures in bulk. This would have to be done after testing. In terms of materials, we learned that ABS plastic or aluminum would be our best options keeping in mind our goals for increased strength and durability of the enclosures without a significant increase in the material costs. Finally, with Craig’s direction, we realized that we should simplify our design to its necessary functionalities and remove showy and unnecessary components such as storage shelves or compartments. This will allow us to decrease cost to increase affordability and decrease size to increase portability and transportability to Zimbabwe.
In relation to the EE team’s touchscreen idea and required volume of necessary electronics, we will be working with an enclosure that is about double the size of the smaller compartment from our unpainted duron prototype from Fall Quarter (new dimensions 6” x 4” x 4”). Our next steps for this week include finalizing on a couple of enclosures in both aluminum and ABS based on the specified dimensions and required functionality, and order a few units of each to start testing out post-machining processes.
Electrical Engineering Team
The EE team looked into a variety of ways to implement the UI elements that we planned on incorporating, including a touchscreen, rotary dial, LED array, and mechanical switches. Ultimately, the team decided on pursuing an LCD touchscreen that unifies the user interface of the box while adding a level of modularity and updatability to the box that should bode well for future iterations. Also, the team is moving forward along the process of incorporating last quarter’s metering circuits into the charge controller PCB so that we can improve the space usage inside the box. Moreover, this should make the product more robust as there will be less loose wiring that can get undone in transport.
Over 1 billion people in the world still do not have access to power. To meet this need, a variety of solar systems have been made available on the market. They typically feature some or all of the following:
Some combination of these features may fulfill the current needs of a customer, but what happens when the customer’s’ electricity needs grow? Say the customer saves up enough money to purchase appliances or devices beyond a light or cell phone? What if the customer wants to purchase and power a refrigerator for her restaurant--or an irrigation for her maize growing farm?
Currently, these customers’ only option is to purchase an entire additional solar system to accommodate their increased needs. But, as their needs continue to increase from the initial standard 10W solar system towards the 6,720W of the average American home,1 they will be forced to participate in this inefficient process countless times. As such, for the global energy poor, their energy systems can inadvertently impede future economic growth, rather than catalyze it as energy access was meant to do.
Our team is working to address this situation by building a system that can grow as customers’ energy needs grow. Essentially, we are designing a solar energy system that can handle a wide range of loads. A customer on our system--instead of having to buy a whole new system with the purchase of a new appliance--could simply buy more solar modules and batteries and plug directly into the system they already have.
And, in the process, we are trying something fundamentally new. What if we could design a system that was so scalable that instead of just accommodating a single household’s loads, the system could be scaled up enough to power neighboring households--and perhaps, even an entire community? These are the types of questions we are exploring at Voya Sol as we build the modular components and metering systems to make this type of solution possible. And in so doing, we hope to test our biggest question yet: Is it possible to build a complete bottom-up electricity grid? We plan to find out.
1. Solar Power Rocks. How Many Solar Panels do You Need to Power Your Home? https://www.solarpowerrocks.com/square-feet-solar-roof/. Accessed 4/8/2019