Re: Beginner Questions

julian814@xxxxxxxxxxx wrote:

> The only other thing I'd like to know for now is of a good source for
> conductive epoxy. I have an old ZX81 computer with a bad membrane
> keypad, and I'd like to see if I could make another. Seems the keypads
> are hard to come by these days.
>
> Thanks for any advice!

I have a ZX Spectrum, bought 1984.

The keyboard gave up a long time ago.

I built a matrix of wires, the horizontal ones lifted up by small
pieces of foam plastic, from a table tennis racket, by the way.

Under it all I placed a picture of the keyboard somehow, so I could
orient myself.
Each contact point between a horisontal and vertical wire is a key on
the keyboard.
When I touch a wire I push it down one millimeter so it comes into
contact with the wire under it.

The rubber pads lift the wire again if I don't push it down too hard,
so it works quite well. Occasionally I need to move a wire when it gets
stuck but it is good enough for playing a little with this old museum
piece.

The first thing you need is a big picture of the keyboard.
I have a vague memory that I cut a picture of the keyboard into
horisontal strips and moved them slightly in relation to each other, so
the pictures of the keys would fit better into a perpendicular matrix.
The key rows on the Spectrum are placed diagonally over each other.

Attach the picture to a base plate, wood or metal, or pcb board
material.

Lay out bare copper wires in a matrix, fix them with glue and prop up
the horisontal wire between each key with some flexible material.


--
Roger J.
.

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