[sdiy] Substitute for pin matrixes?

[John Mahoney]

At 04:32 PM 1/22/2010, karl dalen wrote:
>Any ideas around something that could be a reasonable substitute for
>matrixes? It need to be quite small, small physical space, dead cheap
>and widely easily acquired and have reasonable life time!
>
>[snip]
>Then i got this idea, latching hall sensor that latches a Cmos switch!
>Are there any latching Hall sensors? i.e toggle state whenever 
>magnetic field comes close? One could glue a tiny magnet to a match 
>used to point at switches!
...

Why must they latch -- wouldn't you be leaving the "pin" (magnet) in place?

What about magnets and reed switches? Maybe not dead cheap, but I see 
that Goldmine has some on sale for 35 cents each:
<http://www.goldmine-elec-products.com/prodinfo.asp?number=G1347>http://www.goldmine-elec-products.com/prodinfo.asp?number=G1347 


A bag of button magnets, and you're done. A very quick search shows 50 for $7:
<http://www.magnetvalley.com/index.cfm/fa/items.main/parentcat/4663/subcatid/71826/id/413170>http://www.magnetvalley.com/index.cfm/fa/items.main/parentcat/4663/subcatid/71826/id/413170
A little large, at 1/2" diameter, but you get the idea.

John