This week I spent the majority of my time getting the PCB design ready for shipping. In order to do this, we first had to make some fixes to the battery circuit and power supply. Last week Neha and I realized that we would not be able to charge the batteries up to 5V with a 5V power supply because it passed through a diode and a resistor which caused a voltage drop. After some testing, we found that we were able to increase the input voltage to at least 7V without damaging the ESP32. From this, we can see that we will be able to use a high enough voltage so that we can still charge our batteries.
After this, we had to find out how to power our board, and after some research, I decided on a barrel jack that we could solder into our pcb. We are still determining what the output of this power supply will be, so to accommodate for this, I added in two resistors to our PCB design that can act as a voltage divider to ensure that the voltage that we are getting into our main circuit is the right level. After this, there were some other issues that had to be fixed on the PCB. One of these is that we were having trouble with our eagle library file for the temperature sensor. The metal pads were overlapping, so I had to place three holes instead. I also had to reroute all of the traces that were under the ESP32, because the machine we were using was not precise enough to lay traces between the pin holes of the ESP.
Once the PCB design was finalized, our hope was to create a version ourselves so that we could test it before ordering more online. However, after Neha spent Friday making a PCB with Quinn, we felt that we would not have time to clean up the board to test it, while still ordering the PCBs on time. One remedy that we tried was to use the Bantam machine to see if we could mill a PCB design that we could use for testing, but we had trouble getting the settings right, and we thought that this would also take too long for us to do testing before ordering the PCBs. Finally, Neha and I decided that we would spend time verifying the PCBs and then we would order them. To do this, we wrote out the entire design on a white board system by system and went through each system to make sure that it was wired correctly. In doing this, we were able to find a couple mistakes that we fixed. After this we sent in our order to Quinn to be placed.
Final Design:
Currently the PCB progress is on schedule. We were hoping to have the PCB design sent out for fabrication by now, and we have finished that up. Ideally, this means that we will get the PCBs back this week and we can start assembling them soon. One thing that we are a little behind on is the distributed pathfinding. We have not been focusing on this too much, because we had to get the PCB design finalized, but now that this is done, we will be able to spend more time on the pathfinding and finish this up. We are also a little behind on some of the aspects such as making a video demo and a poster, but I feel that we will be able to finish these tasks once we have our system up and running.
Next week, the first thing that I want to do is to work with Jason and Neha to do our final presentation slides. After this, I want to work with Jason to get the distributed pathfinding completed. Additionally, the PCBs should arrive before the week is over, so I am hoping to start assembling those and placing our components onto the boards. The one other thing that I will do this week is select a power supply and have it ordered so that we can show that our circuit works with wall power and that it charges the batteries. Once we do this, we can also determine the resistors to use in our voltage divider.