Week 7: February 20th - February 26th

Individual Log - Zach

Following the group's meeting I dedicated my time to bring the thermostat enclosure closer to completion. I began by researching different methods that would allow the enclosure to not only interface with a household wall outlet, but also allow consumers the ability to access a pass-through receptacle and plug appliances into the thermostat without losing the capability of the wall outlet. I focused my research on making sure that this feature would comply with ANSI code as well as a number of other household safety codes, but more research will be needed to make this feature truly robust. As it stands, the pass-through will include a 5-15P NEMA and 5-15R NEMA connected via 12-14AWG stranded wire and crimped spades [39][40][41][42][43].

Research continued throughout the week, primarily focused on which LCD screen would allow for the most characters but also be compact enough to keep the design and size of the thermostat enclosure at a reasonable limit. Originally there had been discussion about using multiple 7-segment displays which could have been controlled via independent MAX7219 IC's, but the decision to display all information on one display led to the need for an LCD screen. In the end, the Sunfounder LCD2004 with an I2C adapter was selected [21][22][26][46][47].

A 10k ohm linear potentiometer was selected for "Temp Set" control as a 10k ohm will provide enough range for accurate temperature adjustment.

An Arduino Nano 33 BLE was selected as the MCU for this device following the discussion during the weekly meeting. Bluetooth will likely be a simpler solution that allows the thermostat to communicate with the valve enclosure instead of using a 433 MHz radio [25][28][31].

The abundance of AC/DC converters on the market has led to an exhaustive search for both a compact and efficient module which will continue into next week.

As the week continued, I gathered data sheets for all the components associated with the thermostat to assist with power budget calculations and dimensions [39][40][41][42][43][44][45][46][47]. Using these dimensions I was able to create a mock-up of the thermostat complete with dimensions that should aid us in creating the final CAD 3D model.

To conclude the week, I created a block diagram for the Thermostat Enclosure and updated the website as required.