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I have a TI-84 keypad for the TI-Nspire calculator and I thought it might be interesting to use it in a project as a button matrix. The connector looks like this:

Connector

Unfortunately the edge connector has a weird pin spacing - it's a little less than 1.4mm. I can't find any suitable connectors on DigiKey, Mouser, or anywhere else.

How can I connect to this board? I could of course just solder wires to each pin but I would like to avoid that if possible.

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    \$\begingroup\$ Hi - Is it possible that the "little less than 1.4mm" spacing is really 1.27mm? Considering the age of the calculator, I'd expect an imperial spacing, and 1.27mm is 1/20 of an inch. At least that might be easier to search for regarding edge connectors, rather than searching in mm. You could measure the distance for 20 of the contacts, and see if it is exactly 1 inch. Just a thought... \$\endgroup\$ – SamGibson May 12 at 5:47
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    \$\begingroup\$ No, it is close to 1.39mm. I did have some 2.54mm pins on hand and if it was 1.27mm those would line up with every other pin. It is very close though. \$\endgroup\$ – Darin Mao May 12 at 14:16
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You could make a PCB with pads that are similarly spaced and solder EMI fingers or pogo pins to them. Though then you have to solve how to mechanically support the cards.

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    \$\begingroup\$ Or you can get a flex PCB made that does the same thing, except it flexes. Would be more convenient and easier to solder than discrete wires. \$\endgroup\$ – DKNguyen May 12 at 6:05
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    \$\begingroup\$ I still like the (solid) PCB idea - with conductive foam, as used to connect LCDs to PCBs \$\endgroup\$ – Marcus Müller May 12 at 13:35
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You can create a pcb of the appropriate pitch with castellated mounting holes. They allow a pcb to be directly soldered to a flat pad underneath them. They look like normal plated vias that have been chopped in half. Castellated Mounting Holes

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