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MIDI & Music
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Control Voltage (CV)/Gate to MIDI


Control Voltage (CV)/Gate to MIDI 


The CV/Gate to MIDI unit is capable of converting the output control/gate voltages from a monophonic synthesiser  to a MIDI  note-on/note-off data commands. The unit works with linear CV out Volts/Oct where 0 volt is set to C1 and 4 volt is set to C5. However different MIDI note octave ranges can be pre-programmed, if required.  Each semi-tone is equal to (1/12 = 0.08333 Volt). The gate output voltage from the synthesiser can be between 5 to 15 volts when a note is ON and 0 volt when the note is OFF.



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PRICE:  €50.00



The Control Voltage (CV)/Gate to MIDI unit utilizes:

  • An assembled, built and tested Arduino board including a suitable pre-programmed Atmega168,
  • A 2.1mm power socket, and associated LED, 
  • A MIDI detection LED,
  • A 150mm wired MIDI 5-pin DIN input socket,
  • A 150mm wired MIDI 5-pin DIN output socket, 
  • The circuit schematic is available,
  • The transmit MIDI channel (1-16) can be selected by a 4-way DIP switch. 
  • The velocity byte is preset to half of the maximum value.
  •  The CV to MIDI unit is monophonic




The Control Voltage (CV)/Gate to MIDI unit  also requires:

  • A 9v battery or equivalent DC power source,
  • A Gate trigger LED, and transistor driver,
  • A variable 10k linear potentiometer for scale tuning,
  • A variable 10k linear potentiometer for volume adjustment (optional), plus a 5.1 Volt Zener diode and associated 1k series resistor (optional)






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







Circuit Schematic:

A circuit schematic of the Control Voltage (CV)/Gate to MIDI unit shows the Input/Output connections. 


Power Supply:

The  Arduino 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.




Open the  source code file and copy and paste it into the Arduino programme and save it as a .PDE file.




DIP Switch Selections



4 3 2 1
on on on on 1
on on on off 2
on  on  off on 3
on on off off 4
on off on on 5
on off on off 6
on off off on 7
on off off off 8
off on on on 9
off on on off 10
off on  off on 11
off on off off 12
off off on on 13
off off on off 14
off off off on 15
off off off off 16

Table 1 MIDI Channel




Tuning to a MIDI octave range scale:

When the Control Voltage (CV) is applied to the CV of the MIDI unit, the potentiometer can be adjusted to give a MIDI C7(96) note out when the CV is 4 volts. This tunes the MIDI unit to the scale shown in Table 1 and the rest of the ranges are  tuned. 










0 C3(48) 130.8 0
1 C4(60) 261.6 0.48
2 C5(72) 523.2 0.96
3 C6(84) 1046.5 1.44
4 C7(96)  2093 1.92

Table2 Tuning Scale 


So the CV potentiometer needs to be adjusted to obtain 1.89 Volts out when 4 Volts CV is applied.


The MIDI Note Number to Pitch/Frequency is available and

the MIDI Note Numbers for Different Octaves table is available also.


The unit can be used with the Moog Music Etherwave Theremin.