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DSP Musicolour Pt. 1

This DSP Musicolour accepts audio input signals and drives coloured lights "in tune" with the music. Its four output channels respond to different audio frequency bands and the brightness of the lights is in direct proportion to the amplitude of the frequency components. A dot-matrix LED menu display is featured on the front panel and this also functions as a spectrum analyser or VU meter.

By MAURO

Main Features

  • Full digital design using a DSP microcontroller (dsPIC)

  • Powered from 230-240VAC or 115-120VAC mains with auto-detection of mains frequency

  • Four phase-controlled output channels (8-bit resolution)

  • Optocoupled Triac triggering for complete isolation of control circuitry from output circuitry

  • Zero voltage switching of Triacs for minimum RF interference

  • Four mains outputs rated at 800W each (240VAC) or 400W (120VAC)

  • Selectable gain plus selectable minimum and maximum frequencies for each output channel

  • Selectable filament preheat current for each output channel

  • Persistent software settings

  • Self-diagnostics

  • Chaser modes

  • Direct stereo inputs for audio modulation of lights

  • Microphone input/third channel input for audio modulation of lights

  • 7x15 pixel dot-matrix LED display for menus

  • Dot-matrix display can function as a spectrum analyser, screen saver or VU meter

  • Software-controlled input selection with software mixing

  • Adaptive potentiometer control for software settings

  • Optional provision for ICSP (in-circuit serial programming)

  • In presenting this brand new project, we are reviving a name which became synonymous with party light shows in the 1970s and 1980s. Long time readers will be familiar with the "Musicolour" light shows which were presented in "Electronics Australia", the last one being the Musicolour IV in the August 1981 issue.

    SILICON CHIP magazine followed the same theme with the Discolight project in the July & August 1988 issues and produced a 12V version called the "Lightshow" in the January & February 1998 issues.

    Click for larger image
    This photo and the photo on the facing page show the completed DSP Musicolour boards fitted to the case. The displays have been lit by temporarily powering the Display Board using an external DC supply.

    All of these projects were analog designs based on op amps and logic ICs. The audio was passed through different pass-band filters for each channel and the filtered outputs were used to drive either phase-controlled Triacs in the Musicolour and Discolight circuits or power Mosfets in switchmode in the case of the 12V Lightshow.

    The logic ICs were used in the Discolight and 12V Lightshow to produce the chaser modes, which were alternating patterns controlling the output channels in the absence of an audio input. These chaser modes meant that you could have pleasing lighting effects without any music.

    Two decades on from the Discolight we now present the brand new DSP Musicolour, a full digital design using DSP (digital signal processing). It is based on a single DSP microcontroller to produce a comprehensive list of features that were simply not possible with previous analog designs.

    The DSP Musicolour operates from 230-240VAC or 115-120VAC mains (detecting the 50Hz or 60Hz mains frequency automatically) and drives four channels of incandescent lights. The total power output rating is 2400W for the 230-240VAC 10A version and 1600W for the 115-120VAC 15A version. For the 240VAC version, each channel is rated at 800W maximum (as long as total power is less than 2400W). For the 120V version, each channel is rated at 400W.

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