[sdiy] Substitute for pin matrixes?

[John Mahoney]

At 09:51 PM 1/24/2010, Tony Clark wrote:

>Maybe I'm not quite envisioning this correctly, but you can simplify
>this down to just a single layer of PCB with a hole (smaller than the
>size of the ball)  that has two plated half-rings around the edge.
>When you drop your ball in, it will connect the one half to the other.

That's like what I was trying to describe in one of my magnet-related 
schemes -- pads made of 2 half circles. I don't see how you can do a 
row/column matrix with a single-sided PCB, though, which is why I 
spec'd a double-sided board. One of us isn't envisioning it 
correctly, for sure. <G>

That's when I remembered Nic Collins' writings on the use of computer 
keyboards, which are the cheapest switch matrices that I can think 
of. (No comment on that one, Karl?)

As cool as the ball bearings would look, I wonder if they would make 
for reliable contacts. Also, they could easily be knocked out of 
position, which provides some unusual performance possibilities but 
isn't the kind of UI that I'm looking for. That's why I suggested 
magnets -- personal bias at work.

John