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MIDI 61 Note Keyboard Encoder using an 8x8 Matrix

 

MIDI 61-Note Keyboard Encoder 

 

The keyboard encoder is capable of encoding any number of momentary action, push to make, single pole single throw (SPST), switches from 1 up to 61 to produce the equivalent MIDI note-on/note-off data commands. 

 

The 61 note range is from C2 (MIDI Number 36) to C7 (MIDI Number 96). The keys are arranged in an 8 x 8 (64 keys) matrix. The MIDI Channel is preset to MIDI Channel 1 and the velocity byte is preset to 100. However other values for the MIDI Channel, velocity and the note range can be pre-programmed into the firmware on request.

  

The encoded switches are wired via IN4148 diodes, see switches schematic. 

  

This unit can be connected to new keyboards or it can be used with an older non-MIDI keyboard by using magnetic/reed switches to isolate the old and new scanning circuits. This will allow the older keyboard synthesizer to continue to operate as normal while also providing a MIDI output.


 

 

 

MIDI 61 Note Keyboard

ITEM#: MIDI61KEYS

PRICE:  €45.00


 

 

*Click to Enlarge*

 


 

The 61 Note Keyboard Encoder to MIDI Unit consists of:

  • The MIDI channel is preset to MIDI Channel 1
  • The velocity byte is preset to a value of 100,
  • The start Note of the keyboard encoder is MIDI note 36 (C2) to MIDI note 96 (C7),
  • An Arduino board including a suitable pre-programmed microcontroller,
  • A 2.1mm power socket, and associated LED, ,
  • A MIDI 5-pin DIN output socket and associated 220 ohm resistors,

 

 

The 61 Note Keyboard Encoder to MIDI unit requires:

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

 

Circuit Schematic:

A circuit schematic of the MIDI 61 note keyboard shows the switch connections.

     

MIDI Wiring:

The MIDI IN and OUT connections use 5-Pin 180 degree DIN sockets. Note that the MIDI IN/OUT wiring is polarised and the correct pins should be used. 

 

Use with the 61 Note Ensoniq ESQ1 Synthesiser:

This design can be used with some older 61 note keyboards to replace their faulty electronics. For example with the Ensoniq ESQ1 synthesiser. The Row connections R0 to R7 are connected to 8 Arduino pins D2,D3,D4,D5,D6,D7, D8 and D9 respectively.

 
The Column connections Co to C7 are connected to 8 Arduino pins D10,D11,D12,A0,A1,A2,A3 and A4 respectively. The connections Q0 to Q7 are left unconnected.

  

MIDI Keyboard Wiring:

The switches are organized in a 8 x 8 matrix (64 switches) arrangement. For example, at the top, switches and diodes 0, 6 and 7 are shown but the circuit is also wired in a loop to switches and diodes 1 2,3,4 and 5. Also the other sides of these switches/diodes are connected down to Arduino contacts D2 to D9.

 

So, for example, terminal connected to D10  is wired to one side of the 8 key switches SW 0 to SW7 and the wire can be looped from one key switch to the next.

 

Each of the other side of these switches SW0 to SW7 is wired to a diode on the Cathode (K) side (end of diode with stripe).

The other side of each of these diodes is looped to 7 other diodes. For example Anode (A) of diode DO is looped to D8 then to D16 then to D24 etc. down to D56 and finally to digital terminal D2 on the Arduino.

 

The rest of the wiring is done in a similar manner.

 

Power Supply:.

 External  power can come either from an AC-to-DC adapter 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.