This is an oscillator to be used in a cheap and smelly modular synthesizer, Piezo Chez. It does triangle or saw wave (well, sort of), and by overdrive/fuzz you get pulse wave too.
Properly designed oscillators are complex and subtle circuits, but this is punk electronics. Forget about dual power supplies, temperature compensation and exponential current generation... The engine is a single 4069UB IC, six logic inverters, which are abused as analog amplifiers, it's powered by a 9V battery and output is DC-coupled 9V peak-to-peak (don't connect directly to any expensive equipment).
I got the urge to make this box after reading Elliot Williams on Hackaday. Also see Nicolas Collins: Handmade Electronic Music and Lunettas on electro-music.com, but I think the idea is as old as the CMOS 4000-series.
- Front panel,
- Battery clip (two used)
- PCB (circuit board) could be printed, etching, milling or breadboarding are other options.
Conductive paint, really?
This is how I used the 3D-printed circuit board. After populating the top side with the components, I used conductive paint (called Bare Conductive) rather than soldering. I did try to use the leads of the components as much as possible, but no soldering.
I'll make a second PCB and find out how much the paint is to blame for noise. But, hey, it works.
Copper tape was used as a ground plane.
This is what the top side of the PCB looks like, when populated with components.
5 x 100kOhm (R1, R3, R5, R7 and R8 in schematics)
1 x 33kOhm (R2)
1 x 2.2kOhm (R4)
1 x 220 Ohm (R6)
2x100kOhm Audio tapering (Pot 1, Pot 3)
100kOhm Linear (Pot 2)
3 x 10pF (C1, C2, C3)
1 x 0.1uF (C5)
1 x 0.22uF (C4)
4096UB Hex inverter (Note: gotta be the unbuffered, "U", variant).
BC558B PNP transistor
2 x 3.5mm audio mono jack with normally closed switch to tip.
3 x SPST sub-miniature switch
9V battery connector
4 x M3 machine screws
Component layout (viewed from top)
Revision B of PCB -milled and drilled. Getting posh, are we?
Update (revision B, 29/11/2018). New PCB:
- Proper bypass of Fuzz using double-throw 2-pole switch
- Headers for external power
Box and battery clip: update from Cheesy Electronics Enclosure. The original battery clip was integrated in the box, but was too weak. By printing it flat on the bed it becomes much more durable. The original box also had too small slots for M3 machine-screw heads (so they couldn't be hidden behind the front panel). Fixed.