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Not getting good results from LCD

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spinnaker

Member
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.

J2 is the LCD display.

 
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ericgibbs

Well-Known Member
Most Helpful Member
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.?

Eric
 

granddad

Well-Known Member
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"
 

spinnaker

Member
Two bad displays. :( Just installed a third and it works perfectly.

And I am the one that would yell at the young guys in the shop for assuming the replacement part was good. ;)
 

BobW

Active Member
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.
 

spec

Well-Known Member
Most Helpful Member
Also there might be a supply line problem- supply line too lower voltage and/or no decoupling capacitors.

It is not necessarily true, from the above scenario, that the first two LCDs were faulty- just different characteristics, but still in spec.

spec
 

MaxHeadRoom78

Well-Known Member
You could set up a static test jig as outlined in the Pt1 & Pt2 article by Julyan Ilett, a search will bring the PDF's up.
Max.
 

spinnaker

Member
The issue has been solved. Please read the thread.


Likely two displays from the same ripoff ebay source.
 

granddad

Well-Known Member
Spin, Try turning them off and back on again ...:D

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 ?
 
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