As College of Western Australia electrical engineering pupil Darcy Johnson writes:
There’s a sure intrigue within the unpredictability and complexity of analogue electronics — one thing digital circuits can’t fairly replicate. After constructing a number of digital tasks with microcontrollers and logic gates, [he] wished to dive into the uncooked, hands-on world of analogue circuit design.
For Johnson, this meant constructing a Stylophone-inspired monophonic analog synthesizer from scratch, powered by none apart from the NE555 oscillator (of “simply use a 555” fame). For his aptly named “TouchTone555,” the NE555 gives an oscillating sign that drives an LM358 op amp to energy the system’s speaker. Sound is performed by connecting a probe to the conductive keypad constructed into the unit’s PCB. This emits totally different notes primarily based on the important thing touched and its corresponding resistor.
The TouchTone555 additionally options an RC oscillator for a vibrato impact, and it’s powered by a 9V battery. The design went by three PCB iterations (plus breadboard testing) earlier than selecting the ultimate(?) model. All this work paid off, nonetheless, because it seems to be and sounds superior within the demo video under.
Notably, the unit’s naked PCB is laid out and annotated in such a means that somebody can find out about its operation simply by taking a look at it. Johnson definitely gained a large quantity of expertise in analog electronics and music synthesis through the construct, together with the troubleshooting required to get it to work effectively. KiCad recordsdata and extra information can be found on GitHub if you wish to make one your self and/or additional look at the design.
