[sdiy] Substitute for pin matrixes?

[John Mahoney]

At 07:29 PM 1/24/2010, nicolas wrote:
>Many of the proposals seem oriented towards emulating the 
>compactness of the original pin matrices, but this can be a 
>disadvantage if it is going to be used as a performance oriented 
>playing surface rather than a sound design patch panel.  My idea, 
>which I plan to build, but haven't yet, is for a slightly larger 
>more playable thing a bit like a steampunk monome.
>
>Imagine this:  (The suggested dimensions are for an array at 20mm 
>centres, but when I actually get around to trying this I think I 
>will be scaling it up slightly to a 30mm spacing to make it more 
>playable.)  Three sandwiched layers, at the bottom a PCB with very 
>wide heavy duty tinned tracks for the columns - 15mm wide tracks 
>with 5mm gaps between.  Then an insulating layer 4mm thick with an 
>array of holes - 14mm holes spaced at 20mm centres.  Then rows made 
>of brass strap, 16mm wide, 2mm thick, with 12mm holes at 20mm 
>centres.  All carefully glued together and mounted on a tilt like 
>the tops of many commercial desktop synths.  For pins I would use 
>lead balls 10-11mm diameter.  Steel ball bearings would look better, 
>but I am not sure that the contact would be as reliable as lead.

I've had ball bearings in mind since someone used them in a sequencer 
(?) -- a lovely project of which I can remember little else.

If space was not an issue, I'd go with a pot matrix. Matrix mixers 
are killer, and decent (Alpha) pots are cheaper than high quality switches.

John