Posted on Feb 5, 2014

The Theramidi is a new musical device, based on the Theremin, which produces a MIDI signal relative to the movement of objects to or away from it. The MIDI output is controlled by the intensity of light falling onto two Light Dependent Resistors (LDRs). One LDR determines the note frequency and the other can be programmed to control a variety of M

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IDI effects eg Volume, Modulation etc. (see Table 1). The resistance depends on the amount of light falling on it and this variable resistance is converted by a PIC 16F877 microcontroller into a MIDI signal which can be pre-programmed as in Table 1. At power-on, if the programme switch is simultaneously ON, then the unit will enter programme mode. The 4-Way DIP switch positions are read and stored in the EEPROM, and the unit will operate as shown in Table 1. Programming the Light to MIDI Unit only has to be done once and the switch positions are stored internally in the EEPROM and the unit will continue to operate in this mode, even when power is removed, until reprogrammed. Operation mode is set via DIP switches 1-4 (See Table 1) in programme mode which allows the unit to produce linear/logarithmic etc. responses to the movement of an object (e. g. a hand) blocking the light falling onto the LDR.

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