We examined sound waves and an Electronic Circuits, by putting together a small keyboard.
The synthesizer is build around the NE555 timer chip and a resistor-ladder.
![](https://homeschool.dk/wp-content/uploads/2019/10/syn1.jpg)
Parts
![](https://homeschool.dk/wp-content/uploads/2019/10/syn3.jpg)
Diagram
![](https://homeschool.dk/wp-content/uploads/2019/10/syn2.png)
Below is a screenshot from »Engineer’s Mini-Notebook« by Forrest Mims from 1984. This version uses a lot of different capacitors which makes it more expensive. The previous DIY version shown above is very cheap compared to this one.
![](https://homeschool.dk/wp-content/uploads/2019/10/syn4.jpg)