I began this week by repairing prototype three. I ordered a new uSD reader and swapped out the old one. After I got the new reader installed properly everything worked perfectly. I still do not know what exactly happened with the old uSD reader but hopefully whatever it was won’t happen again. If it does I will have to try to look at the connections on the breakout board and see what is breaking there and figure out if I can design one that won’t break.
In addition to repairing prototype 3 I created prototype 4. I figured that it would probably be good to have redundant devices with gyroscopes in case an uSD reader or something else broke we wouldn’t be stuck until I could fix it. Prototype 4 also had the side purpose of providing a test platform for the homemade gyroscope breakout boards. I built the prototype before I had the new gyroscopes so I made sure to build it in such a way that I could easily slide the commercial or new gyroscope on depending on what worked. I ended up being able to use the new gyroscope which meant that prototype 4 is approximately 30mm shorter than prototype 3.
This leads to the biggest accomplishment of the week, the new gyroscope. Is was rocky going getting it up and running but I eventually got there. The first task was to learn how to use the new solder reflow oven. A solder reflow oven is a fancy convection oven that cycles through different temperatures for different amounts of time so that it can melt and cool solder past in the ideal way for surface mount soldering. The instructions that came from it were in chinese and badly translated english, so they were not the most helpful. Once I figured out how to use the oven I found out that it does not heat as quickly as I would have liked so I had to spend time trying to set the cook times and temperatures in such a way to get the temperatures I actually wanted for the amount of time I actually wanted them. After that I had to figure out how to apply solder paste to spots that in some cases were only a few millimeters in size with a couple millimeters separating them for the pads next to them. This was a very slow and meticulous process. The first time I tried it, it did not work. There was a short somewhere on board. This was really scary since I didn’t know what was wrong. There were a huge number of possibilities, the board had a design problem in it, if I just applied the solder wrong, if I reflowed, wrong or simply that the solder paste I was using was expired so it flowed strangely. After the first one didn’t work I did not know what to do, so I got some new solder past and just tried again praying for the best, and it worked. I successfully designed a board in eagle, solder surface mount components onto it and connected it to a prototype device to take real data.
All the time this week I didn’t spend soldering either the new prototype of the gyro board I spend in google designing breakout boards with all the necessary components integrated onto a couple boards. I am nearly done and can hopefully send the designs off to be printed sometime next week.