xylophone

xylophone elektor december 1980 — 12-09 With Christmas practically on the doorstep, small, sound producing circuits become very popular. This novel circuit, although not entirely original, has been included mainly because of its simplicity and, by making use of the printed circuit board, can be constructed very quickly — just in time to replace that forgotten Christmas present! This design again makes use of reed switches, only on this occasion they have a different function. By placing several of them next to each other, a form of keyboard is obtained which can be played by means of a magnet attached to a wooden stick. The circuit diagram of the xylophone is shown in figure 1. Eight reed switches are used to make up a single octave. Closing any one of them will start up the oscillator. This consists of N1, C1 and the resistor in series with the closed reed switch. As the value of C1 is fixed, the actual frequency of the oscillator is determined by the combined value of the pa...