Matrix board!

[jorgen.bergfors at idg.se]

>>I think Juergen H bought some of these a year back or so >and had the bad experience that there was no "resistor pins"
>>available for that matrix board, only diodes and shorts!
>>
>>Also ,i think the farnell matrix is awfull small too!!!!

>For the cost, especially with the pins, you would be miles better
>actually making a 1/4 inch jack field, cheaper and tougher.
>Remember, when you are buying stuff by the hundreds the price
>halves at least.
>Also, the flexibility of patching in and out!

I just got the idea to use 2,5 mm stereo jacks. They are cheap and take less space than the 3,5 mm variety. You can mount them with 8,89 mm (3,5 in) spacing. That leaves enough room for the plugs too. On a 3 HE panel you can fit 13 rows (12 if you want room for text). My idea was to connect two different sources and one destination to each jack. With two different types of plugs you can then select which source to connect to the destination. That cuts the number of jacks in half. Of course you use resistors in the plugs. If you want to connect both sources in the same jack, you can make plugs with two resistors.
So a matrix with 24 x 24 connections will take 132 x 240 mm panel space, including space for labelling. Of course you can make the matrix any size you need.
The jacks are $0.34 each, if you buy 25, at my supplier (www.elfa.se). So total jack cost for the above matrix (not counting plugs) would be $97. I suppose you could get them even cheaper if you buy that many.
You would mount the jacks for each column on a vertical circuit board. Then you connect all boards with a horizontal board using headers. So no wiring to the jacks will be needed. This way, the matrix can be disassembled if a jack goes bad and need to be replaced. You can also add columns as you need them.

What do you think?

/Jorgen