This week, I was a little busy because of two midterms that I had, so I was not able to get as much done as I had hoped, but I was able to make some good progress. First, during class, Neha and I were able to get the smoke sensors working. However, one issue with the setup that we had is that the output was unusable. We tried adjusting this by putting a resistor on the output pin, but this did not seem to help too much. After doing some research on this part, we found that they are often shipped already attached to a PCB. When looking at this PCB, we could see that the sensitivity of the device was set through a potentiometer. I think that using a potentiometer to fine tune our resistance would be a good idea for us as well. Once we have this dialed in, we can decide on a resistor to use for our final PCBs.
For the PCB design, I was still unable to find a library for the MQ2 sensors that we are using. Because of this, I decided that I would have to create my own part. This consisted of 3 stages. First, I had to create a footprint for the device that specified the location of the pads. For this I had to do some mild trigonometry based on the specifications in the datasheet, as these were given in polar coordinates, but Eagle takes rectangular coordinates. Then, I had to create the symbol which just consisted of me creating the shape that would appear on the schematic. Lastly, I had to make the device, connecting the pins of the symbol to the pads of the footprint. After all of this, I was able to add my part to the schematic that I have been working on. I learned a lot about Eagle from this, and I think that this is going to help us as we finish up our PCB design. I was going to add a picture, but I couldn’t get WordPress to accept it, even when I reduced the size.
Lastly, I also met with Jason this week to begin integrating our pathfinding and LCD display code. However, not too long after we started, we realized that we would need to make some changes to the code before they could be integrated. The LCD code was fairly easy to modify, but the pathfinding code will need a few changes before it can be integrated.
Currently, I am a little behind schedule on the PCB design. Creating the custom smoke detector was one of my goals for this week, and I did complete that, but we had hoped to have this finalized by last week. However, this week, we spent some time looking into alternative fabrication methods, and I believe that by making the PCBs ourselves, we will be able to save some time and money. This is how I think that we can make up the time in our schedule, as we leave a couple weeks in our schedule for manufacturing and delivery. We are also behind in our pathfinding integration and testing, but my schedule this next week is not very busy, so I believe that Jason and I will be able to spend a good amount of time and hopefully finish some of this before the interim demo.
Next week, I am hoping to create a final PCB design that includes all of our components. Including the batteries. I am also hoping to get the display integrated with the pathfinding code. Currently, I have put a pause on the distributed pathfinding, as Jason and I would like to get a version working before we start on the other version. I would also like to look into integrating communication with pathfinding. The one other thing that I need to do is look at battery holders for our AA batteries and pick some to order or 3D print.