Solar Powered 40106 Oscillator

The past month or so I saw an interesting post by Ian Watson so I messaged him to find out what he used.

Simple square wave oscillators using a CMOS 40106 hex inverter and some passive ring mods.

I didn't include ring modulators in this design but I might go back, experiment and incorporate these at some point or in future builds. He also discussed playing around with the capacitors in this circuit and looking at the starve section.

Here it is being run through a pitch shifter.

Power Section

Between the solar panel and the circuit I wanted to experiment with voltage starve, seeing as the panel I had was 9v and CMOS chips normally work between 3v and 15v. I found a 10k pot worked very well for this as larger pots seemed to give a very small range at one end.

I think I could even get away with 4.7k if I were to build this again as only 50% of the range is no response (although I've not tested it on a proper bright day).

With most of my Lunetta circuits I normally build the same power  regulator on the input using a large cap of some type between +/- followed by a 1n400x and after a 104 cap.

I experimented with the large cap found that this not only altered pitch but would rise and fall in pitch as the largest caps filled up, this was nice but I wanted the option for instant power as well so I put 2 different electrolytic caps on a DPDT switch.

To make better use of this I also added a push to break button to have an instant drop in power and make use of this larger caps Attack/Decay behaviour on the circuit.

Six Voice Oscillator

Made using a CMOS 40106 hex inverter with hysteresis. Theres a great section in Nicholas Collins Handmade Electronic Music and in Elliot Williams Logic Noise Articles that cover creating these simple sound circuits.

Outputs

I wanted the ability to split the different outputs as pairs (basically each pair had the same cap value) but also mix them together if I wanted, I had some switched mono jacks so I created a cascaded output. If nothing was plugged into output 1 it routed to output 2 and if no jack was plugged into that it went to 3.

Each pair was mixed with diodes and a 10k load resistor to ground (Nicolas Collins' book helped me understand this).

Housing

Well, I went all out on this, I'd recently purchased a cheap CNC machine to learn how to create wood panels for my modular Lunetta, this project was massive learning curve in using that. I managed to create a panel and a cap for the starve button.

Lessons Learned

I tested the circuit at every stage, and modified it based on how it sounded and felt.
Never try putting a circuit together late at night. I built the circuit and rushed it causing me to start from scratch.

Building a case...

This took the most amount of time and I want the ability to potentially replicate the process. An hour and a half is too long to be running a CNC, I've started to look at creating rubber stamps for labels of basic functions, that way I could easily replicate this process and cut down on the build time.

I also wasn't happy with the way the lettering turned out, after staining the panel I started wondering how to make the labels stand out, I used a thinned down white oil paint but this made a mess and I wasn't happy with it.

Next time - Stain/Paint Panel > Stamp > Varnish > Done.

Developing this further

Around the time I was building this Tom Whitwell of Music Thing posted a device based off a circuit by Ralf Schreiber.

Schreiber's work is based around minimalist robotics, I was particularly interested in his autonomous audio kinetic installation work.

After further research I came across a circuit that he used in some of his installation works http://www.ralfschreiber.com/solarsound.html and I hope to build this with a 5v panel as I have some spare 74HC14 chips.

I also didn't realise that I'd grabbed some of the panel wood I used to make my modular and that the Sundrone Synth was the exact row height of my wine crate cases.

I'm now considering a whole case of solar powered devices alongside some passive elements...

Progress Picture

DIY Synth Case and Power

Progress...

This is probably the third version of this system, after having a bit of a nightmare with the first system and weird ground issues I then tried to make a version with jack sockets but due to the nature of plywood I then used coffee stirrers to reinforce the sides to stop the panels from flexing and potentially breaking when inserting jacks.

After having a think I realised that it would cost more and be a nightmare to glue coffee stirrers onto my wooden panels each time, I went back to my original plan of bolts and made sure the power was right by having caps and diodes on the power inputs for each module.

I'm really happy with the way this third version is faring so far. Heres how I made the case and power.

Case

Theres a wine merchant in the local town and they sell some really nice alcoholic products, the bonus to this is that they come in wooden boxes that then have to be disposed of. If there's an event on locally one weekend then I know that they normally have a few in stock and they're free.

Some thick strips of MDF were used for cheap mounting rails for the panels.

Wine crates often come in standard sizes and as the height of bottles rarely changes I means that 2 rows of 152mm tall panels is perfect.

Power

The power panel is taken from the wonderful guide at castlerocktronics.com and I created a bus board with a 9v regulator taken from Nicolas Collins Handmade Electronic Music.

So this system runs off a 12v rechargeable battery and will supply unipolar 9v and 12v.