Potential solution to the continual screen flicker and continual contrast variation problem, and it’s cause, is suggested at the end of this article.
Photo 1 (below): The back of the PCB before the LCD is removed.
Photo 2 (below): Removing the LCD from the PCB carefully with long nose pliers.
Photo 3 (below): the PCB after the LCD is removed, with the LCD sitting on the table below.
Photo 4 (below): the ‘Spongy’ PCB to LCD’ contact (see this in photo 5 of 5 below) aligns with the row of 9 contact pads seen at the top of this photo. The connection made is not good with my modules. This causes much screen flicker and contrast variation.
Photo 5 (below): ‘Spongy’ LCD contact seen at top centre of LCD module in last photo below.
Photo 6 (below): A quality clean pencil eraser used to clean the zebra contact.
Photo 7 (below): Cleaning the spongy zebra strip.
Photo 8 (below): Flexing the metal can that holds the LCD so that there is a slight downwards arc in the middle that will cause the fore to be evenly distributed when the ends/ corners are tightened onto the PCB.
The ‘spongy’ contact from the LCD, see at the top of photo 5 above causes screen flicker and much contrast variation by not making good contact with the 9 contact pads on the PCB (photo 4).
WHAT CAUSES THE SCREEN FLICKERING AND CONTRAST VARIATION PROBLEM? These Nokia 5110 screens are, as I understand it, ‘rescued’ from old Nokia 5110 mobile phones. During the phone dismantling process the spongy contact part of the LCD screen is removed or ‘dis-contacted’ from the original contact pads on the phone board (the equivalent in the phone of the 9 pads shown in photo 4). The original quality of contact is never again achieved. Because somehow the LCD screen is mounted on the PCB break out board incorrectly. Is solder paste or some other conductive ohmic Ω adhesive missing?
SEE THIS SOLUTION:
http://www.youtube.com/watch?v=EEXihSheOZU
PARTIAL SOLUTION: I found on re-assembly that if I adjusted – with the long nose pliers – the 4 ‘twisted contacts’ that attach the LCD to the PCB, as shown in photo 2, I could adjust the pressure with which the LCD spongy contact is pressed onto the PCB. I was able to get the display output to be perfect. Then, as I took my hand off the LCD board to put it on the table. the screen went off , because the amount of pressure applied by my hand, holding the module, changed the pressure on the spongy pad. These display devices due to being mounted incorrectly on the PCB are very sensitive. Are yours?
MORE IDEAS / POTENTIAL SOLUTIONS:
- Clean all contact surfaces. To do this use a clean quality pencil eraser on the strip, and on the contact pads. I did this and it really worked for me.
- Place a shim on top of the LCD glass (display side) using a narrow strip of self-adhesive tape. Then place the metal can that contains the LCD back on top of the LCD. This can help apply pressure when the metal can is re-fixed. I did not do this.
- As a final resort you could double flip the zebra connector or replace this. Search for “elastomeric connector strip” or “zebra elastomeric connectors”. I did not do this as I did not want to break the solid apparently permanent contact between the LCD and the elastomeric connector// zebra strip.
If you know how to better clean the ‘spongy’ elastomeric contact strip or how to get it to make an acceptable (better) connection with the contacts on the PCB I’d like to know.
Perhaps solder paste, or some sort of conductive glue, or other paste, or other answer exists?
Please leave a reply with your thoughts, thanks
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I have had no problems like this and have used many of these boards, but the breakout boards vary in quality, pin order, and even polarity of backlight pin, and it probably depends mostly which supplier you use.