In keyboards with no contacts, or in such a bad shape it's not worth restoring, this set of boards might be useful. HALKA stands for HALL Keyboard Adapter
and uses hall-effect magnetic sensors to detect key state. This is fully integrated keyboard scanner and it connects to master MIDI controller by just one 4-wire cable.
Works just like any other scanners of MIDI-hardware, so it can be put in a chain with other scanners. Logically it is an equivalent of
Hall sensors simplify keyboard MIDIfication, because it's easy to achieve trigger point repetability of about 1mm or better. It all depends how magnet and sensors
are located with respect to each other. See the examples:
You can also exchange ON with OFF locations from examples above and it still works, because Halka automaticaly detects normal position of the key, whether the magnet
approaches sensor when a key is being pressed, or moves away from it. To add more flexibility, the order of notes is user configurable. It can go up or down, so it's
possible to install HALKA with cable on the left or right side of the keyboard.
HALKA consists of 4 separate boards that need to be mounted on a firm base that does not bend easily, for example a block of wood, or aluminium profile with isolating washers.
Mounting holes are 2.5mm in diameter. This 4-piece construction alows for adjusting to actual keyboard size. Keys may be of different width, as it is mostly the case
in older wooden keyboard. When properly aligned, the boards must be secured with screws, and then soldered together using short pieces of wire. Be careful not to short
the pads during soldering. This is low profile keyboard scanner to fit anywhere, but it also means the distances between soldering points are small.
Boards dimensions are: 3 longer ones - 213x15mm, one last shorter - 170x15mm. Distances between sensors are fixed at 13.4mm.
Overall thickness is 3.2mm at highest point. Connectors at the back side protrude up to 4.8mm.
Installation procedure is described in the manual at the bottom of this page
Unlike most of hall-based keyboards, HALKA draws low current to operate without compromising latency. One set of boards for 5 octaves draws about 15mA, so it's possible
to build 4 or more manual organ console with them, and still be able to power it from 4 AA batteires for many hours.
download user manual
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