I gave a workshop as part of Super Public Art School (for a second time) in Titanik Gallery 6 June 2013. The topic was a hand shake between visual and sound arts: a synthesizer pencil. I named it Synakynä (a pencil synth in Finnish). Below you can witness some fooling around with first working (after many failed) prototype.
Synakynä is augmented version of drawdio but it uses ATtiny85 microcontroller instead of a 555 timer. This greatly expands the sonic range of the instrument. At the workshop, preprogrammed ATtinys are provided, but if you wish to modify the code and upload it by yourself, source code for Synakynä is available and written using Arduino IDE. One also needs to install ATtiny definitions. To upload the code you can use either ISP programmer or Arduino board as described in previous link.
To play Synakynä, you need to draw continuous and as thick line as possible on paper while touching one end of the line with your other hand. This will cause a small current to flow through the circuits of the pencil, your drawing and your body (study the diagram above for the details). The microcontroller is measuring amount of current and using this information to alter pitch of the synthesizer and tempo of blips. It is also possible to replace pencil with more or less anything (fruits, food, skin) that has similar resistance. Feel free to experiment.
The current code has multiple different modes written into it. Every time Synakyna is switched on, different mode will be chosen.
- Pencil (HB,2B, as soft as possible)
- ATtiny85 (+ optional 8-dip socket)
- 300k resistor
- 680pF capacitor
- Power switch
- Battery holder (2032)
- Battery (2032, 3V)
- Piece of spot board (22×9 holes)
- Metal wire, uninsulated
- Piece of aluminum foil or copper tape
- Soldering iron and solder
- Wire strippers
- Knife or saw
- Pencil sharpener
The circuit board is constructed on spot board by using thin metal wire to form the actual circuit. It is a neat little technique that is for some reason surprisingly rare. Compared to etched or strip boards this technique allows improvising the actual layout of the board on the fly without spending huge effort on layout design. Those not keen on improvising can find a fairly compact layout below.
Stuff drawn with pen are on the copper side of the board while parts drawn with pencil are on top side of the circuit board. Pay attention for the trace going to the left leg of the piezo. It should go past the trace coming from the power switch at the top side of the board. Diagram is from the top side (the side the components are) of the board.