Connecting 0.6mm pitch smt pads to an arduino to control COG LCD

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Scaniox

Joined May 21, 2020
1
I want to use the LCD display from a Casio fx-85GT X classwiz calculator as I think it will be a fun and challenging project to figure out the display protocol and connect the display to a much more capable processor on a custom PCB; then I could program a calculator with more interesting functions and have control over the firmware.

I need a way to connect the 0.6 mm pitch roughly 35 pin surface mount pads (shown in the attached photo) to some pin headers so I can control the display with my arduino or teensy 4.0 through a voltage divider.


So far I have tried using an old elastomeric connector I scavenged out of an energy monitor to connect it to pads on a breakout PCB with the same pitch, but the connection has a very high resistance when there is continuity at all.

What other options are there that I could use aside trying to find and buy a COG LCD with the same dimensions instead?
20200519_121523.jpg
Here is another identical lcd from a much more broken calculator:20200519_144848.jpg

Thank you in advance for your ideas and suggestions.
 

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jpanhalt

Joined Jan 18, 2008
11,088
Welcome to AAC.

That display looks like it has crack in it (bottom pix). Does it still work?

As for the connection you seem to show (top pix), was the FPC/FFC ribbon cable soldered originally or did it use a conductive past and clamp?

As a general response, there are lots of connectors that could be used for connecting the FPC ribbon cable to your PCB. If the cable has been removed from the display, that is the only problem.
 

MisterBill2

Joined Jan 23, 2018
13,673
The product to make the connections you seek is commonly called "Zebra Strip", and is commercially available. And the company offers a lot of application assistance and information. Of course, there are many cheaper products also availabe and some of them may sort of work sometimes, for a while. I do not recommend them.
 

jpanhalt

Joined Jan 18, 2008
11,088
The product to make the connections you seek is commonly called "Zebra Strip", and is commercially available. And the company offers a lot of application assistance and information. Of course, there are many cheaper products also availabe and some of them may sort of work sometimes, for a while. I do not recommend them.
It appears the TS has already tried that,
So far I have tried using an old elastomeric connector I scavenged out of an energy monitor to connect it to pads on a breakout PCB with the same pitch, but the connection has a very high resistance when there is continuity at all.
 

MisterBill2

Joined Jan 23, 2018
13,673
It appears the TS has already tried that,
There is a HUGE!!! difference in quality between what the TS tried and a new GOOD strip. So any comparison is meaningless. A worn out, well used piece of the cheap stuff is not similar to a new piece of the good product. AND this sort of application is the kind where quality and condition do matter.
 
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