Hello again,
@MAS3
I have tried to omit the Serial connection completely and it seems to be only related to whether I print the timer or if I try to print the text. I just used the serial connection to check if it was the arduino or the LCD that messed up and since the arduino had no problems with the serial connection even if the LCD was messed up, I moved my attension elsewhere.
@bperrybap
You're absolutely right it is a BC517 transistor, must have been a "typo" on my part. I know the symbol was not right which is why I wrote what it was exactly next to it, but I only had a short time to draw the schematics down so I decided to use the symbol that you see.
I have not even started to use the transistor but thank you for pointing it out. I will definitely make sure to add a current limiting resistor. As far as I can see a 4.7kOhm resistor should do quite okay.
I didn't know that it was a problem using the D13, but I will take that into account. I want to make a new PCB as I have gotten my hands on an Engraver. With that I should not risk having bad cupper leads on the board.
Grounding issues
Nicely spotted! I do infact have problems with my ground, I used the oscilloscope on the ground between the arduino and the LCD and I actually have a potential difference that is quite substantial. I have enclosed a picture of the measurement
I do not have the possibility to fix that right now as I am away for the weekend, but I will do it first thing next week! It is indeed looking more and more like it is the actual PCB that is the problem. So maybe bad etching when I made it. It is going to be exciting to see if fixing the ground can eliminate my issue.
l²C
The only reason I did not use l²C was that the only LCD I had with that was a 20x4 and I wanted to use 16x2. I have thought many times though that I should change it around and with this I might just do so, if I have to make a new PCB anyway.Thanks for the hints on the library, will definitely check it out.