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MIDI Five Row Chromatic Button Accordion (CBA)

 

MIDI Chromatic Button Accordion (CBA)

chromatic_button_acc_pic.jpg (96070 bytes)

  

This is a design for a reedless MIDI Chromatic Button Accordion(CBA). Some of the advantages of such an instrument are instant key changes, via MIDI, and the ability to practice with headphones (silently to the outside world).

  

The chromatic keyboard has more than one system. It can have anywhere between three and six rows of small round (and sometimes rectangular) keys. The fourth, fifth and sixth rows are mechanically linked repeats of the first three rows, to increase fingering possibilities. The two most common layouts are the B and C systems

  

This keyboard encoder is capable of encoding a number of momentary action, push to make, or magnetic or hall effect switches for a Stradella Bass 120 key, and up to a five row 61 or 65 key Chromatic Button Accordion (CBA), utilising a ready built, assembled and tested MIDI encoder key-switch interface.

  

The Treble/Melody notes are on MIDI channel 1. The chord buttons are on MIDI Channel 2 and the Bass notes are on MIDI Channel 3. Other switch arrangements can be assigned if required. The encoded switches are wired via IN4148 diodes.

 

This unit can be connected to new keyboards switches or it can be used with an older non-MIDI keyboard by using magnetic/reed switches or hall effect switches.

 

 

MIDI CHROMATIC BUTTON ACCORDION 65 NOTES

ITEM#: MIDICHROMBUTTACC65

PRICE:  €75.00


 

*Click to Enlarge*

 


 

 

MIDI CHROMATIC BUTTON ACCORDION 61 NOTES

ITEM#: MIDICHROMBUTTACC61

PRICE:  €75.00


 

*Click to Enlarge*

 

 


 

 

 

The MIDI Chromatic Button Accordion Stradella Encoder Unit consists of:

  • The MIDI channels 1, 2 and 3 are preset, 
  • The velocity byte is preset to a value of 100,
  • An assembled  Arduino MEGA,
  • A 2.1mm power socket, and associated LED, 
  • USB power or external power choice,
  • A MIDI 5-pin DIN output socket,

 

 

The MIDI Chromatic Button Accordion Stradella Encoder unit requires:

  • a 9v battery or equivalent DC power source
  • Suitable key-switches or magnetic reed switches or hall effect switches and associated IN4148 diodes

 

Circuit Schematic:

This unit  uses the ATmega 2560 microcontroller and can be powered from an external 9 Volt DC power supply/battery or via the USB connection.

 

This design has switches SW0 to SW23 which are arranged as shown in the MIDI Stradella Bass/Chords Mapping diagram. This mapping also shows the  MIDI Note numbers for each switch.  . The Bass and chords can be transposed by +/- 1 Octaves, controlled by an Octave + switch and an Octave - switch.

 

The System C 65 Note, 5 Row, Chromatic Button Accordion layout is shown in the MIDI Chromatic Button Accordion Mapping.

 

The System C 65 Note, 5 Row, Chromatic Button Accordion circuit schematic diagram is available. This arrangement produces MIDI Note numbers 27(D#/Eb) to 91(G). The melody notes are on MIDI channel 1.

 

Also a  61 Note, 5 Row, Chromatic Button Accordion circuit schematic diagram is available. This arrangement produces MIDI Note numbers 31(G) to 91(G). The melody notes are on MIDI channel 1.

 

Hall Effect Wiring:

Here is information for the wiring of the Hall Effect devices.

There are also circuit schematic diagrams for the MIDI Chromatic 65 Button Accordion with Hall Effect switches and the  MIDI Chromatic 61 Button Accordion with Hall Effect switches.

 

Videos:     

Here is a video showing how the Root and Major 3rd rods/levers lift one at a time when a button is pressed and here is a video showing when a single bass chord button is pressed 3 rods/levers are mechanically activated simultaneously.

    

MIDI Wiring:

The MIDI  OUT connection uses a 5-Pin 180 degree DIN sockets. Note that the MIDI OUT wiring is polarised and the correct pins should be used. 

 

Power Supply:

The  Arduino MEGA can be powered via the USB connection or with an external power supply. The power source is selected automatically. 

 

External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. A low dropout regulator provides improved energy efficiency.

 

The board can operate on an external supply of 7 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

 


 

Stradella Bass/Chord Switches:

The Stradella switches are organized in a 24 x 2 matrix arrangement. 

 

Bass Switches:
The lowest note  is switch SW0 wired via diode D0 between Pins 23 and 34 of the Arduino MEGA.

The next note  is switch SW1 wired via diode D1 between Pins 25 and 34 of the Arduino MEGA.

The next note  is switch SW2 wired via diode D2 between Pins 27 and 34 of the Arduino MEGA.

The next note  is switch SW3 wired via diode D3 between Pins 29 and 34 of the Arduino MEGA.

The next note  is switch SW4 wired via diode D4 between Pins 31 and 34 of the Arduino MEGA.

The next note  is switch SW5 wired via diode D5 between Pins 33 and 34 of the Arduino MEGA.

The next note  is switch SW6 wired via diode D6 between Pins 35 and 34 of the Arduino MEGA.

The next note  is switch SW7 wired via diode D7 between Pins 37 and 34 of the Arduino MEGA.

The next note  is switch SW8 wired via diode D8 between Pins 39 and 34 of the Arduino MEGA.

The next note  is switch SW9 wired via diode D9 between Pins  41 and 34 of the Arduino MEGA.

The next note  is switch SW10 wired via diode D10 between Pins 43 and 34 of the Arduino MEGA.

The next note  is switch SW11 wired via diode D11 between Pins 45 and 34 of the Arduino MEGA.

 

 

Chord Switches:

The next note  is switch SW12 wired via diode D12 between Pins 25 and 36 of the Arduino MEGA.

The next note  is switch SW13 wired via diode D13 between Pins 27 and 36 of the Arduino MEGA.

The next note  is switch SW14 wired via diode D14 between Pins 29 and 36 of the Arduino MEGA.

The next note  is switch SW15 wired via diode D15 between Pins 29 and 2 of the Arduino MEGA.

The next note  is switch SW16 wired via diode D16 between Pins 31 and 36 of the Arduino MEGA.

The next note  is switch SW17 wired via diode D17 between Pins 33 and 36 of the Arduino MEGA.

The next note  is switch SW18 wired via diode D18 between Pins 35 and 36 of the Arduino MEGA.

The next note  is switch SW19 wired via diode D19 between Pins 37 and 36 of the Arduino MEGA.

The next note  is switch SW20 wired via diode D20 between Pins 39 and 36 of the Arduino MEGA.

The next note  is switch SW21 wired via diode D21 between Pins 41 and 36 of the Arduino MEGA.

The next note  is switch SW22 wired via diode D22 between Pins 43 and 36 of the Arduino MEGA..

The next note  is switch SW23 wired via diode D23 between Pins 45 and 36 of the Arduino MEGA.

   

Each of the other side of these switches SW0 to SW23 is wired to a diode on the Cathode (K) side (end of diode with stripe).

The other side of each of these diodes, the Anode, is looped to  other diodes. 

  

CHROMATIC SWITCHES:

The Chromatic switches are organized in a 12 x 6 matrix (up to a maximum of 72 switches) arrangement. Some switches are repeated using similar MIDI numbers in different switch positions. 

 

This is a link to the Registers of the Standard Stradella Keyboard.