NE555-3-scale electronic keyboard V1.0

Basic concepts of
notes and scales: Any one of 1, 2, 3, 4, 5, 6, 7, and i in the simplified notation is called a note, and the whole is called a scale
. The relationship between notes and frequency:
From this table, we can see that two adjacent There is a definite 2-fold relationship between the frequencies of the corresponding notes in each scale.
 
The basic principle can be found from this. Changing R1, R2 or C1 can change the frequency characteristics
of the output square wave. 1. The scale and note can be controlled respectively. 2. The scale can be changed by changing the series and parallel relationship of the capacitor. Special instructions 1. The resistance value in the schematic diagram It is a theoretical value, not a nominal resistance value. When using it, you should choose a resistor with a similar resistance value, or use multiple resistors in series. 2. The PCB is arranged according to the pattern of perforated boards for the convenience of soldering verification using perforated boards.