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DSP Musicolour Light Show; Pt.2

In last month's first part, we described the circuit operation of the DSP Musicolour. In this instalment, we guide you through the construction. The operation of the firmware and troubleshooting tips will be described next month. In this issue there are also notes and errata for the schematic published last month.

By Mauro Grassi

Before we start any construction, let's make a couple of things perfectly clear about the complexity and skill levels needed to build the DSP Musicolour.

(1) This project is not suitable for beginners. In fact, you should not attempt to construct this project without considerable experience, particularly with mains devices.

(2) This project controls mains (230/240V or 110/120V) voltages. Mains voltage can be lethal. Hence it is especially important to double check and be certain that mains power is not applied whenever working with the PC boards.NEVER apply mains power to the main PC board unless it is fully enclosed in a plastic case with the case screws done up.


All the parts in the red shaded area on the Main Board component layout diagram (Fig.3) operate at mains potential (ie, 240VAC) and contact with any of these parts could be FATAL.

These parts include the PC tracks, the opto-couplers (OPTO1-4), the Triacs, the 100mH inductors, the 680W resistors, the 100nF 250VAC capacitors, screw terminal blocks CON4-CON6, the transformer primary and the wiring to the mains input and output sockets. DO NOT TOUCH any of these parts unless the power cord is unplugged from the mains supply. DO NOT CONNECT this device to the mains unless it is fully enclosed in the specified case.

This project is not for the inexperienced. Do not build it unless you know exactly what you are doing and are completely familiar with mains wiring practices and construction techniques.

Construction: Display Board

Click for larger image
The main and display boards assembled in the case, before the rear panel (and rear panel wiring) is fitted. This prototype photo has single-sided PC boards - production boards should be double sided to eliminate most links. However, if you etch your own PC board it will probably be as per the prototype and require links as shown above.

The DSP Musicolour is built on two separate PC boards. The main board consists of the Triac output section at 230/240VAC mains potential and the low voltage section containing the op amps and the dsPIC30F4011 microcontroller. The two sections of the main board are isolated by optocouplers and the mains transformer. The vertical display board is all low voltage circuitry and its supply rail is +5V.

We'll begin the construction with the display board, which is coded 10107082 and measures 247mm x 76mm. Note: our prototype DSP Musicolour used single-side boards with many links, however kitset suppliers are likely to provide the boards in double-sided form with plated-through holes, in which case only a few links will be necessary.

First, you should check the PC board for hairline cracks in the tracks and any visible shorts between tracks. Fix any defects.

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