This is the EmTronic mini synth, it's a super simple Arduino powered noise maker that I have designed to be easy to build and only requires easy to buy parts. This little synth allows you to control frequency, modulation and the waveform of the sound.

The Arduino sketch uses the awesome the_synth library from DZLOnline.

The 3d printed front panel finishes off the mini synth but you don't need it to make the sounds. You could even build it on a breadboard if that works for you.

Best of all once you're done it's time to experiment with your own mods to the software to make new crazy sounds and mods to the front panel to really get the look you want.

At some point I will sell few finished EmTronics for those who don't want to make their own so check out my store some time at Rarebeasts.

Happy noise making

Brian McNamara

Supplies

Arduino Nano
10k pcb mount vertical pot(RV09)
Tactile push button switch
1/8" audio socket(PJ392)
2.2uF radial capacitor
About 40cn of Wire
3d printed front panel and support arm, you don't need this for it to work but it's fun
Mini-B USB cable

Tools:

Soldering iron

Solder

Hot glue gun

Side cutters

Wire strippers

Pliers

A computer to loaded with the Arduino IDE and the_synth library(https://github.com/dzlonline)

Step 1: Solder Pots

In this step we solder the 10K pots to the Arduino Nano.

Take the two 10k pots and bend the middle pins of each one so they face straight out.
Cut the 2 middle pins of the pots to allow just enough tab for you to solder a wire onto later.
Solder the pots to the Arduino as shown in the photos, one goes between the GND and 5v pins on the side and the other goes on the GND and 5v pins on the end.
Solder small lengths of wire to the middle pins sticking out from the pots.
Solder the ends of the wires to A0 and A1 on the Arduino.

Step 2: Fit the Audio Output

In this step we solder on a capacitor and the audio socket to the Arduino. The cap just filters out some of the high frequency noise from the Arduino, you can use a 10uF cap if you find the output is still too noisy.

Take the 2.2uF capacitor and bend the wires so they neatly fit between Pins D7 and D11. The capacitor is polarity sensitive so make sure the - side goes to D7 and the + side goes to D11.
Solder wires on each leg of the capacitor.
Now solder the wire from pin D7 onto the long tab of the 1/8in audio socket.
Now solder the wire from pin D11 onto the two small tabs of the 1/8 audio socket. If you strip the wire back a bit further you can fit it through the holes on the two small pins.

Step 3: Fit the Push Button Switch

In this step we add the switch to the Arduino.

Take the push button switch and remove 2 legs using the photo as a guide.
Solder the switch between the GND and D3 pins on the Arduino with one side of the switch resting on the side of the Arduino reset button.

Step 4: Make the Front Panel and Put It All Together

Now we print the 2 parts and fit the Arduino.

Print the front panel from the supplied file, I printed it face up with a 0.25mm layer thickness.
Print the support arm, I printed mine on its side with a 0.3mm layer thickness.
Now slide the Arduino assembly into the back of the front panel, the 2 pots and the switch should just slide in.
Fit the audio socket into front panel and tighten the ring nut.
Now use some hot glue to hold the Arduino in place.
Fit the support arm to the bevel on the front panel, it should just slide on.

Step 5: Program the Arduino

Ok now we program to the Arduino, you need the Arduino IDE and the the_synth library for this.

Download the Arduino IDE and install it on your computer.
Download the_synth library from https://github.com/dzlonline , you may need to look up how to add the library to your specific operating system but it's not hard.
Download the arduino sketch from above.
Connect the EMTronic to your computer via the USB cable(just a hint, make sure it's a data cable and not just one for charging)
Load the Arduino sketch Emtronic_2020.ino into the IDE and hit the upload button.

Now hook up a speaker or head phones to the EmTronic and check that it works.

EmTronic_2020.ino
Download

Step 6: How to Play

It's pretty simple, have fun exploring the sounds.

When you plug in the USB to the EmTonic it is automatically powers up.
The top pot controls the frequency of the synth.
The lower pot controls how quickly the sound is repeated giving a modulation effect.
The switch cycles through the different wave forms; Sine, square, triangle, saw, ramp and noise.

Step 7: This Is the Fun Bit

Now that you have made the EmTronic the fun begins, go and modify the software to make cool new sounds or change the design of the front panel, a wooden one would look great. It's now up to your imagination to create the synth you want, have fun with it.