I have two displays doing the same thing. I it appears to be a contrast issue. Below is the best I can get the contrast adjusted. Notice how part of the P and part of the M appear to be washed out and there are artifacts all over the screen.
I have never had this problem before and think I have used 10k trimmers in the past.
I am using a 10K single turn trimmer. Considering swapping it out for something larger but before I do I wanted to run it by others first.
hi spin,
I have used both 5k and 10k contrast pots on the LM104L, 2*16 LCD, worked OK.
When using 4 Bit operation, I prefer to leave the low nibble pins , D3 > D0, open circuit and not linked. [ try it]
The right side 8 characters of the two lines are faint blocks, which I would expect.
Are the two LCD's new devices or recovered from other equipment.?
Hi spin, It looks like an internal address (LCD) problem more that a contrast the first 8 addresses bad , next 8 OK etc etc or it might be a timing issue , how fast do you repeat " RPM 0"
The links to your images are broken, so I'm not sure what you're working with. Though it's certainly possible to get two bad displays, it is rather suspicious. I wonder if the code that's running the display has some borderline timing issues.
Edit.. 7 March 13:26 GMT
My bad Its what you get if you ring a help desk in the UK .... , I thought my post was quite humorous , I may be wrong but sometimes it takes some time for comments to catch-up the thread in all countries ?