[sdiy] 61 Note Keyboard from Electronic Goldmine

[Scott Stites]

Hi all,

I ordered one of those 61 weighted key keyboards from Electronic Goldmine,
and received it tonight.

http://sales.goldmine-elec.com/prodinfo.asp?prodid=8280

For $39.95, it's not a bad buy at all.  Each key does have a metal weight in
it, and it's spring action.  It's got a good feel to the keys, but I really
don't have anything good to compare it to.

The switches are the membrane type, and there is something about this
keyboard I didn't expect:

The diode matrix has 122 diodes - two diodes for each key.  The columns are
attached to the anodes of the diodes in pairs for each key.  The cathodes
each are switched into two different, separate rows by the keypresses - in
other words, there are twice as many rows as a 'standard' diode matrix.  The
rows are as one would expect - 8 keys to a row, except for each 8 key row,
there is a duplicate 8 key row that is switched in separately with the
'second' diode.

The membranes are cup shaped.  Around the 'rim' of the cup is one conductor
which switches one diode.  In the 'bottom' of the cup is another conductor
which switches the other diode.  Now, I'm not sure about this, but it seems
that the 'rim' conductor switches the first diode earlier in the travel of
the key, and the diode in the 'cup' switches the other diode later in the
travel of the key.   This could be my imagination - I'll know better when I
can put two DMM's on it and check, but judging by eye, that seems to be
what's happening.

Could this be used for some type of velocity or after-touch function?  I'm
not familiar with this arrangement at all (I don't get a chance to dissect
too many keyboards).  If anyone knows, please enlighten me!

I'm tickled pink with this keyboard, I'll post pictures of it on my web page
if anyone else is interested in scoping it out in better detail than
Electronic Goldmine provides.

Thanks for the bandwidth,
Scott