Working on the Typewriter
I decided to save time and use a shell script and systemd service to run the typewriter software on the raspberry pi. It works perfectly and automatically starts up when you give it power.
Unfortunately the typewriter ran out of ink. We had some spare cartridge, but they were not compatible with the typewriter. We wanted to see if we could take the ribbon out of the old typewriter cartridge and put it into the new one.
I am still in the process of doing the transplant but it seems like it will work.
Assembling the Float
We finally had everything in place and we could start to build the float. We put it together and were able to test it. Once we got the firmware uploaded to the microcontroller it worked. It successfully moved the piston and stopped when it hit the magnet.
After the successful test we went to lunch. When I came back I noticed that the microcontroller had stopped working. I tested the pins on the voltage input and noticed that it was only supplying 1.5 volts when it should have been supplying 3 volts.
I proceeded to check the battery pack inside of the float and started to feel a burning sensation. After washing my hands, I realized that one of the batteries in the pack had exploded and leaked hot battery acid throughout the float. I could see some of it had made it to the aluminum stopper and was bubbling agressivley.
I quickly got rubber gloves and took the float apart to clean off the battery acid. It did some significant damage to metal, and minimal damage to the plastic. I had to take apart the float quicker than usual because it was actively being eaten by the battery acid.
While I was trying to quickly take it apart I damaged the PCB. Thankfully we were able to easily mill and new one and soilder headers to it again.
Although we did not end up with any significant dammage it could have been very bad if I did not notice it as quickly as I did.
Trying to Find the Cause of the Leak
We wanted to find what could have caused the leak after this happend. We wondered if we had a short somewhere so we intentionally shorted some AA batteries to see if they would fail in the same way. Although they got very hot they never opened.
We then wanted to see if we somehow dammaged the casing when we installed the batteries, so we scored the batteries with a knife, and it still did not fail.
After waiting 30 minutes we wanted to see what would make it fail, so we hit the batteries with a hammer and they eventually failed, but it multiple dents and significantly dented the batteries.
We do not know what could have caused the problem, we think it might have been do to faulty cells, and we hope it does not happen agian.