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The TheraMidi


The Theramidi


The Theramidi is a new musical device, based on the Theremin. The TheraMidi produces a MIDI signal relative to the movement of objects to or away from it. The MIDI output is controlled by the intensity of Infra-red light reflected from objects ( e.g. hand movements) using two Infra-red transmitter/receivers. 


One Infra-red device determines the note pitch/frequency and the other can be pre-programmed to control a variety of MIDI effects e.g. Volume, Modulation etc. However the default control is Volume. The MIDI Channel can be selected with a 4-way DIP switch.


The centre pitch is C3 (MIDI note 48) and the pitch range is +/- 12 semitones using MIDI pitch bend from C2 (MIDI note 36) up to C4 (MIDI note 60). The start centre note can be pre-programmed to any required note.

Details of the MIDI Note Numbers for Different Octaves is available.



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The TheraMidi 


PRICE:  €50.00






The TheraMidi utilizes:

  • An Arduino board 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 1
  • A 150mm wired MIDI 5-pin DIN input socket,
  • A 150mm wired MIDI 5-pin DIN output socket, 
  • A MIDI activity associated LED,
  • The circuit schematic is available,




The TheraMidi requires:



Circuit Schematic:

A circuit schematic for the TheraMidi shows the Infrared connections. The design uses two Infrared Proximity Sensors from Sharp GP2Y0A21YK which has an analog output that varies from 3.1V at 10cm to 0.4V at 80cm. Other  Infrared Proximity Distance Sensors with analog outputs can be used but the software may need to be adjusted to get the correct ranges.




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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.









The  Theramidi units can be combined/expanded by connecting the MIDI OUT of one unit to the MIDI IN of the following unit.





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



Details on Pitch Bend and Pitch Bend Range Sensitivity adjustment.


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.