This week I spent a lot of time meeting with Kaashvi and the rest of our team to try and finalize the hardware that we want to order. This is because originally we were all under the assumption that the nodes would be made up of arduinos. After looking at the inventory, we realized that if we wanted to use arduinos, it would get really expensive really quickly. So, we decided to branch out to using other microcontrollers and we decided that NodeMCU ESP32 was our best option. Once we figured out this part, we started to move on towards finding the exact Zigbee shields that we needed after learning that these are actually quite expensive as well. Then we started to look for development boards that had Zigbee capabilities included and realized that either they were not released to the public just yet or they came from unreliable sources. As of now, we think our best option would be to use regular NodeMCU ESP32 development boards and buy a couple Zigbee shields just to prove that in the event that the wifi connection went out, we have a working solution for how to get around it when it comes to scaling up for our demo. We put in an order and hope to get them reviewed and sent out as soon as possible. Once we have the microcontrollers we also finalized decisions on the displays which we sent out as well. We wanted to ensure the displays we picked were big enough for users to read while being in a hurry to get out of the building but also compatible with the ESP32s and shipping from a reliable source. Trying to get a balance of these three components was a bit tricky but we think we found a good selection of displays and sent those out to be ordered as well. Further, we are still waiting on our smoke sensors as they were shipped from ebay which will take until March 1, but we were thinking of finding smoke sensors from a more reliable distributor so we can get and test them as soon as possible. Finally, our temperature sensors came in this week and on Friday we were able to use an arduino just to test its capabilities and thresholds using a lighter. We kept note of the delay of recognizing the temperature and how long it stays at a certain threshold before cooling down. We also added an LED to detect certain ranges and turn on/off at different cutoffs. All of these considerations will be present in our design review presentation.
According to the Gantt chart, my progress seems to be on track. It has been a little frustrating not getting the parts completely ordered but I’m glad we were at least able to test the temperature sensor as it aligns with our schedule. Ideally we could’ve tested smoke sensors as well and instead of using an arduino we could use the ESP32s but we only made that decision later in the week so we tried to keep up with our schedule in this way. We were also able to scope the battery requirements and send out a request for the batteries we want to use for each node which is on track with what we had planned. But those orders we placed will likely only go out next week. All in all, I am pretty much on track with what we had proposed but we anticipated a quicker turnaround time for all of the parts that make up the structure of our nodes.
In the coming week, I want to be able to find a good smoke sensor from a reliable source and start testing that immediately. I also want to figure out how we need to wire the battery to the rest of the node so we can be able to recharge it in the event of a power outage and allow this to be the source of power when necessary. Once we figure out how these circuits are configured and the layout of the ESP32s, we can utilize our Eagle research and plan how we want to design and fabricate our PCBs. We also know that our design report is coming up so we want to make sure that we have a finalized plan and can explain any design choices that we make and show the progress we have made towards those plans.
This week, the ECE courses I have been working on the most have been circuits as well as some software systems with the arduino/microcontroller programming (specific courses would be 18-220, 18-349). These courses aided in support for diodes to recharge batteries, arduinos to read data from sensors and power LED, and general decision making and design planning considerations regarding the research we have been involved with this week. Outside of these courses, we spent a lot of time researching online to learn about what is going to work best with our design (ie what sensors/displays are compatible with certain microcontroller, what batteries fit the design requirements, etc.).