Build your own MIDI projects
Frequently Asked Questions.
MIDI & Music
MIDI and Music Information
MIDI to 8 Outputs




This unit utilizes MIDI Note ON/OFF data to switch 8 Relays which can be used to control electromagnets.


This unit can work in standard MIDI mode or via the USB connection. It defaults to standard MIDI Baud rate of 31250. By replacing the original firmware on Mega8u2/16U2, the Arduino Uno will act as USB-MIDI device (Standard Midi Class), you don’t need to install additional device drivers on Windows, MaxOSX, and Linux, as the firmware acts as a device of Standard Midi Class. It will automatically install on the system as an Audio USB Device.


Note that this unit is designed to work with Veil software. Veil is a musical instrument. Thin fabric spans in front of you; touch it, strum it, bend it, the fabric responds and generates a sound. A continuous feedback process happens between your movements and the simulated movements of the veil. Instead of playing music directly through Veil, you can use it as a MIDI controller. Move your mouse to access the settings. There you find a list of available output ports.



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MIDI Notes to 8 Outputs


PRICE:  €110.00









The MIDI to 8 Outputs unit utilizes:

  • An Arduino including a suitable pre-programmed Atmega microcontroller,
  • A 2.1mm power socket, and associated LED, 
  • A 4-way DIP switch, which selects the MIDI channel, shown in table 2
  • A 150mm wired MIDI 5-pin DIN input socket,
  • A 150mm wired MIDI 5-pin DIN output socket,
  • Output Note selection is preset in the firmware, 
  • The circuit schematic is available,
  • MIDI IN/OUT circuit schematic,
  • An 8-Way Relay board.



The MIDI to 8 outputs also requires:

  • A suitable 12 Volt DC power source


Circuit Schematic and Boards:

A circuit schematic of the MIDI to 8 Outputs unit,

A circuit schematic of the 8-Way Relay Board,

8-Way Relay Board single electromagnet wiring,

8-Way Relay Board multiple electromagnet wiring,













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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.





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Output Current Drive:

You can get a maximum of 40 mA (milliamps) current from each output separately. But the maximum combined rating when several pins are active at the same time  is 200 mA for all pins. However it is probably best not to run the outputs at their maximum rating.


Normal Mode:

The unit detects the incoming MIDI data and if the MIDI channel corresponds to the correct MIDI channel setting, when a corresponding Note-on is detected, (to the pre-set note-on  data), the corresponding output is switched on (0 Volts) and stays on until the corresponding note-off is detected and the output is switched off (+5 Volts). This allows each output to operate independently. 


C Major Penatonic Scale


With the Veil software using the C Major Pentatonic scale the 8 relays are controlled by the top 4 and bottom 4 notes


With the Veil software using the C Major Pentatonic scale the 8 relays are controlled by the top 4 and bottom 4 notes as shown in the Table 1 below.




1 C2 84
2 D2 86
G2  91
4 C3 96
5 C-1 48
6 E-1 52
7 A-1 57
8 C0 60

Table 1 MIDI Channel



The tuning details  shown in Table 1 explain the Notes and corresponding MIDI Note Numbers. Note that the MIDI pitch specification here assumes 12-edo tuning.




The MIDI to 8 outputs unit can be operated live in real time from a MIDI keyboard or from a hardware/software sequencer with pre-programmed MIDI Note on/off data. The outputs can be used to switch electrical devices, such as lights, motors, pumps etc., in time with the music. Use the outputs to control and synchronize auxiliary circuitry.



MIDI Specification: 

The outputs are switched ON via MIDI 'Note-On' commands and OFF by MIDI 'Note-off' commands. These MIDI commands are all channel (1-16) dependent. Also, the outputs will switch off if  a correct MIDI Note On with a velocity of 00  is received. The unit also works in MIDI Running Status mode.





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 2 MIDI Channels



Power Supply:

An external 12 Volt DC power supply can be used to power the external electromagnets and also the Arduino if it is not using/powered by the USB connector.


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.


Or else connection from the 12 volt power supply can be inserted in the Gnd and Vin pin headers of the POWER connector. A low dropout regulator provides improved energy efficiency.