This week, the group got together to revise the engineering requirements, specifications, and materials list per the panel's advice after our presentation on Friday, 12/2/22.
First, the group refined the engineering requirements. A standout comment from the panel was that our top high-level requirement should be expressed as a percentage, rather than a temperature range. After further discussion, the group decided that the device shall remove heat from a parked car such that the maximum internal temperature is no more than 130% of the maximum ambient temperature. The group chose this number because the inside of a car can typically reach temperatures 147% greater than the ambient temperature after sitting in the sun for an hour or longer [1]. The group saw their prototype achieve an average internal air temperature that was a maximum of 138% of the outside maximum ambient temperature, 9% less than the expected maximum without cooling. The prototype only used a total of eight fans in the rear of the vehicle. Since the revised design will double the number of fans and include fans in the front and the back, it stands to reason that the device will decrease the percentage by another 8%.
Other changes to the requirements include the removal of redundancies, clarification of verification and success criteria, a minor reprioritization, and the addition of a low-level requirement that states the need for an indicator LED for the window proximity monitor. The updated engineering requirements can be found under the Project tab.
Next, the engineering specifications were updated to reflect the changes made to the requirements. Most notably, the specifications for an LED Indicator were added.
Next, the group went about updating the materials list and budget to account for any items which were out of stock or which did not meet the specifications. The Adafruit MCP23017 was out of stock, so the group decided on the ADAFRUIT PCF8575 to replace it. Upon further research, the group determined that the EDECOA Battery Cables 3 AWG were too short and that 3 AWG was not necessary, so they were replaced by 10 Gauge Wire (10ft) and a Schumacher BAF-TTC Zinc-Plated Top Terminal and Post Washer Set. The group also added Loctite Threadlocker Blue 242 Nut/Bolt Locker to the list.
Once the budget was verified to be correct and in stock, Daniel set out to get everything ordered while Ian created a checklist to keep track of item costs, shipping costs, totals and ordered/received items.
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