- Joined Sep 17, 2007
Please help me to design a metronome circuit. Thank in advance.
A metronome is an instrument to help making music. The rhythm can appear as a brisk/vigorous beat or a flashing light. The signal can be given out of a small speaker (16 Ohm) or LEDs in different colours.
The main beat has to be distinguished by a stronger beat or a different coloured LED. Using LEDs the light may burn only for a part of the time in between the beats. The number of beats per bar (2, 3 or 4) is to be chosen by connecting a single cable end alternatively. Number of beats per second is 2 3.
There are as special components CMOS-devices 4060 (oscillator and 14-stage binary counter) and 4028 (BCD decimal decoder). Still there are a few 4001 (quad 2-input NOR), 4023 (triple 3-input NAND), 4049 (inverting buffer) and 4081 (quad 2-input AND) for those in need.
4000-series devices use metal gate CMOS-technology and they can be operated directly from 9V battery. Their inputs load is comparable to a 5pF capacitance and there flows no direct current. The outputs rating is not sufficient to be loaded by a speaker. In between even a bipolar transistor is usable, but better take a MOSFET. Available is BS170 (n-channel, 5 Ohm) and NDF0610 (p-channel, 5 Ohm). The volume can be adjusted by supply voltage.
In order to get a sound only at certain edge directions, the speaker can be connected by a suitable capacitor in series to the speaker and a parallel-connected resistor to discharge the capacitor. Choose time constants for suitable pulse lengths.