7
Scanners
MBBS board is the merging point for all keyboard and potentiometer scanners.
Depending on their sizes, the whole system can cover up to 5 keyboards with 319
keys over single MIDI socket together with 64 potentiometers at the same time.
Currently available sizes are: 32, 64 and 128 keys, the last one has the 128 keys
grouped in 2 keyboards. For analog (pots) there are boards with 3 and 12 inputs
7.1
PDS - diode matrix pedal scanner
Pedal board controller takes care of 32 keys and two analog inputs, usually all
what's needed for pedals with 2 swell shoes. It's a small board that fits inside pedal
board, and it connects to the main board via
supplied 4-wire cable from J2 connector. 4 pads
labeled in this picture as J3, are for
potentiometers. The picture shows how to connect
the pots, and also in which pot position you get
the maximum, or minimum value of given MIDI
parameter controlled by the pot. Go to chapter 4
for more about potentiometer connection.
Keys must be connected in diode matrix exactly like in the schematics below:
The groups of 8 switches with 1 common lead must be separate. In case
of keyboard with 1 common bus bar going through entire keyboard, you
have to cut the bar every 8th key.
7.2
DMS-2K dual keyboard matrix scanner
For keyboards with diode matrix ideal solution is DMS-2K, adding 128 inputs. This
can be described as "diode matrix driver" for 2 keyboards. The layout is shown on
the next page. There are two 16-way connectors, used to connect diode-matrix
keyboards. Smaller connector is to connect with main controller board - MBBS. The
keyboards must have “8x8 scanning diode matrix”, that's very simple circuit, made
of diodes forming electric XY matrix. Usually all modern keyboards are equipped
with it although sometimes the matrix is organized differently, in 5x12 or 6x11. In
such case you must rewire the diodes, or order customized DMS-2K.
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