This describes how to build and program an Arduino-Uno-style, polyphonic, pentatonic synthesizer. Original Synth (OS) is designed to be cheap, customizable, and marginally entertaining.
This project is designed for an Arduino kit plus a few accessories.
Arduino Kit est. $35
4.7nF Capacitor est. $0.40
Headphone Jack est. $0.95
Extra Button (x3) est. $2.50 for a 20-pack
Headphones: Wherever you can find a pair, or use a set of computer speakers. (worst case: 50 cents / pair of headphones)
Estimated Total Cost: $39.35
1) Setting up basic Arduino
You will need the Arduino IDE (integrated development environment). Get Arduino set up and running on your computer. Follow the instructions here.
Open the IDE. Try some of the examples from the File>Examples tab first to confirm that your setup is working.
2) Setting up the Synthesizer Library (mozzi)
Mozzi is a fantastic synthesizer library that Original Synth relies on heavily. In order to speed up the setup process, the Mozzi library as of 19 July 2019 is included in this repository. In order to use it, copy the mozzi directory and all of its contents located in this repository's arduino_libraries to your Arduino 'libraries' directory (the location of which depends on your installation process - look for the directory where you installed the Arduion IDE).
Once this step is completed, you should be able to view example Mozzi sketches using the File>Examples>Mozzi dropdown tabs.
The final test: open osynth.ino and attempt to compile it (click the checkmark in the IDE) - if it compiles without error (i.e. there's not a flood of orange text) then you've got Mozzi installed!
[Coming Soon: Circuit Diagrams]
First, familiarize yourself with how the electrical connections on a breadboard work
The basic unit of Original Synth is the button circuit. The basic circuit is a button, a 330-Ohm resistor for that button, and an LED between the two. The LED will light when you press the button.
[ BASIC BUTTON DIAGRAM GOES HERE ]
Repeat this pattern six times, starting at the far left of your breadboard.
[PICTURE OF ALL 6 BUTTONS]
NOTE: The button is set up across the big gap in the middle of the breadboard so that it's easier to press without wires getting in the way later.
NOTE: Wire Colors:
- Try to use red (and other 'warm'-colored) wires for connections to the red
+(positive voltage) row on the breadboard - this will make it easier to keep track of what wire goes where. - In addition, try to use blue (or green, or black) wires for connections to components that ultimately go to the
-(ground) row on the breadboard.
This unit allows you to listen to the synth. Use the smaller breadboard included with the kit.
[IMAGE OF SMALLER BREADBOARD]
In order to filter out high-pitched noises that happen when you're synthesizing tones on an Arduino you must construct a low-pass filter.
For Mozzi in particular, the output signals come from digital pins 9 & 10 on the Arduino Uno. For more on the headphone circuit, refer to the documentation at https://github.com/sensorium/Mozzi/wiki/Output-circuits,-filters,-amplifiers,-etc.-(*-this-has-content
Instead of a 1 Mega-Ohm resistor (recommended on the page) you should use two 1 Mega-Ohm resistors (from the kit) in parallel to create an equivalent 500 Kilo-Ohm resistance. For more information on resistance & resistors see here.
Instead of a 3.9 Kilo-Ohm resistor you should use 2 2 Kilo-Ohm resistors in series to creat a 4 Kilo-Ohm equivalent resistance.
[PICTURE OF RESISTORS ON THE SMALL BREADBOARD]
Next, connect the terminal ends of both sets of resistors to your 4.7nF capacitor. This circuit will now protect your ears from troublesome high-frequency noise.
[PICTURE OF HEADPHONE JACK CIRCUIT WITH CAPACITOR ADDED]
Next, install the headphone jack on the breadboard and connect the ground (black) and signal (yellow) wires as shown.
[PICTURE OF HEADPHONE JACK CIRCUIT WITH HEADPHONE JACK COMPONENT WIRED UP]