Introduction: NoiseAxe MiniSynth

This Project is Mini Synthesizer, using a PICaxe. It was designed by Brian McNamara. If you're looking for a mini drum machine, you should check out his other project, The GrooveAxe. His other project is the MemAxe

You can get the kit from Gadget Gangster & grab the schematic. here. The kit comes pre-programmed. But, if you'd like to gather the parts yourself, you'll need the following.

Parts list

  • Resistors, 1 each of : 1k, 3.3k, 330, 560, 100k, 2.2k, 220k
  • 4 x 10k Resistors
  • Gadget Gangster project board (half board)
  • 10 uF Cap
  • 8 Pin Dip Socket
  • 3xAA battery holder (and batteries)
  • 10k Photoresistor
  • Micro Speaker
  • 22Ga Hookup wire
  • And a programmed PICaxe 08M. You can get the Source Code off Gadget Gangster
You'll also need a soldering iron, solder, and wire cutters.

Here's a little video demonstration

How to Play It

The NoiseAxe will play 8 different notes, each note is played by touching one of the 8 resistor legs at the bottom right of the PCB with the stylus wire. You can change the level of modulation by varying the light that enters the photoresistor, creating a vibrato effect. This is done by putting your finger over, or shining a small LED torch onto, the photoresistor.

How it Works

The NoiseAxe is based around the Picaxe 08M micro-controller. The 8 different notes that it will play are controlled via a stylus that you use to touch each of the 8 resistors legs at the bottom right of the PCB. Each resistor makes a voltage divider that produces a different voltage when that resistor is touched. The voltage is sensed by the ADC (analog to digital converter) on the Picaxe and converted into one of 8 values in the program. The 8 note output corresponds to one octave on a keyboard. The sound command is then used to output the correct note to the speaker. The photoresistor is also used in a voltage divider circuit connected to one of the inputs the micro-controllers ADC. A digital value is read within the program and added or subtracted from the frequency sent to the sound command.

Step 1: IC Socket

Place the 8pin IC Socket on the top side of the PCB, with pin 1 on G4 of the PCB and pin 8 on J4 of the PCB. Solder into place.

Step 2: Wire Links

Solder the wire links to the top side of the board at coordinates:
-E2 to Q2
-L4 to Q4
-A4 to F4
-D6 to F6
-D10 to E10

Step 3: Resistors

Place the resistors on the top of the PCB at the following coordinates:
- R1; A12 to L12 330R
- R2; A13 to L13 560R
- R3; A14 to L14 1K
- R4; A15 to L15 2.2K
- R5; A16 to L16 3.3K
- R6; A17 to L17 10K
- R7; A18 to L18 100K
- R8; A19 to L19 220K
- R9; L6 to Q6 10K
- R10; E5 to F5 10K
- R11; C6 to C10 10K

Step 4: Capacitor

Solder the 10uF Capacitor to the top side of the PCB, with the positive leg at L7 and the negative leg at L8.

Step 5: Photoresistor

Fit the photoresistor to the top side of the PCB with one leg at A6 and the other at B6. Solder in place.

Step 6: Stylus Wire

Cut about 4 of wire. Strip both ends, and solder one to K6. Leave the other end free.

Step 7: Battery Box

Solder the Red wire on the battery box to A1 on the top side of the PCB.
Solder the Black wire to E1 on the top side of the PCB.

Step 8: Speaker

Cut 2 pieces of wire about 2 long, strip both ends and solder one end of each wire to each terminal of the speaker. Solder the two wires to K8 and Q8 on the top side of the PCB.

Bend the wires to place the speaker in the place were you want it.

Step 9: Fit Picaxe

Fit the Picaxe 08M to the 8pin IC socket on the PCB.

Step 10: Fit Batteries and Test

Fit the 3AA size batteries to the battery box. Turn the NoiseAxe on and check for sound by placing the stylus on each of the 8 resistor legs that terminate in row L.

That's it! To grab the schematic, source code or to order a kit, check out the project on Gadget Gangster.