Weekly Update: Week 7

EE/Software Team

We finished setting up the touchscreen display and started developing a user interface to display the quantities which we meter. We ran into some issues with the SD card reading and realized that the read time for images would be so slow that we would be better off drawing out a UI using the library’s drawing functions instead of displaying an image that we designed offline. Also, we obtained our PCB samples and assembled the components with the gracious help and mentorship of Sawson, an EE PhD. Everything seems to be working great with the exception of the solar charging, which we are actively working to diagnose and solve. Below you can see a picture of Sawson debugging the circuit while Caroline celebrates that her phone is charging when connecting the battery to the PCB.

Design Team
We received a machining sample from Polycase, the same company that we bought the encasings from, and we evaluated the machining quality. In the next couple of days, we will decide whether the price for custom machining is worth the time we will save on making 30 iterations of our box in the PRL with the available tools. Below you can see the machining sample we received, which shows features with similar dimensions than the ones we would request, and with a very good quality - clean chamfers and even cuts.
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Additionally, since we have the first three assembled PCBs, we are now updating the hole spacings on the encasing CAD model to adapt to the real dimensions and distances between the USBs and the sharing port. Below you can see our first functional encasing prototype, which includes holes for the USBs and sharing port on the long side (left) and holes for the solar panels and the battery cables on the short side (right). This prototype was made in the PRL with the available tools to test the placement of the electronic components, which we are working on.

Sourcing
    During the past week, we have continued working to establish high-volume, reliable, low cost suppliers for solar panels and batteries.   Since we are developing a product for very low income customers, finding the lowest possible cost is an absolute must. This creates a challenge during the early testing phase because the lowest cost suppliers are based out of China.  Importing from China creates 3 main challenges:

1. Customs
   1. Importing commercial goods such as solar panels and batteries requires customs clearance.  The high volume suppliers that we need to work with in order to minimize costs do not handle shipping the way that you might expect from ordering other household goods from China.  There is a long list of different “trade terms” that describe the ways in which the responsibility for stages of the shipping process is distributed. In the end, our team must be involved in the customs clearance process.
2. Shipping Time/Expense
   1. We first need to obtain samples from each supplier in order to verify product quality before we integrate their product into our own.  There are 3 high-level shipping options from China to Palo Alto, CA (below). Unfortunately, in order to receive samples in a timely manner, we end up paying much more for the goods than a domestic alternative because of the added cost of air freight.
      1. Sea transport to LA - 20 days - cheapest
      2. Sea transport to SF - 35 days - mid price
      3. Air freight - 5-7 days - expensive

 

1. Quantity
   1. As an early-stage start-up, we do not have the buying power that is often needed to purchase commercial goods (at a low cost).  We are currently aiming to create 30 units for a field test, but the minimum purchase order for most of our ideal suppliers is between 200 and 500 pieces.  Delicate negotiation has been required to convince the suppliers to meet our needs.