Fortune Wheel / CV based LFO Generator

[Baran Ismen]

Hello dear folks.

For a while, I've been working on a project. It's solely based on Tom (a.k.a ElectricDruid)'s StompLFO LFO signal generator. A while ago, I asked here how to make such a basic LFO circuit, some may remember. Then I made one with a 555, a basic one indeed, and it worked as well, but then StompLFO really drove me crazy with its capabilities and I ordered one. Tom was so great to send along a OneShot signal generator chip as well for a trial.

After a long time of trial & error and the massive support of Tom (thanks a million, again), I've finally managed to finalize my project. I named it "Fortune Wheel".

For anyone who doesn't have any clue; StompLFO is basically a signal generator with 8 different wave types & shapes and can be used with any pedal that has expression input on it, so that you'll have sort of an automatized expression pedal. Further info and its datasheet can be found here. I mainly followed the schematic provided here with some minor differences such as pulse LED and output voltage regulation for my pedal in use (a Behringer DW400)

Later, I decided to merge StompLFO and OneShot Event Generator (details here) in a single board and separated their signal routes with a simple SPST switch, so that when the pedal is on, both chips are powered, signal route can be changed between StompLFO and OneShot instantly. Both circuits share the very same pinouts and such, so it's two birds with one stone.

As these chips and their rights solely belong to Tom and their schematics are actually shared within their datasheets already, I wanted to share my own versions of the schematics with the public (which I assume would not be a crime, right?). I also uploaded the pictures of the layouts I've prepared, if anyone wants, I can gladly send the 1:1 PDF files of the layouts.

I'll try to upload some audio clips as well to show their capabilities.

Enjoy!

[Mark Hammer]

My original idea that I pitched to Tom for the One Shot, was for something that would/could be used to modulate modulation.  Hit the momentary switch, and the One Shot could make an LFO speed up, slow down, or progress from the one to the other and back again, or rise, rise, and rise then stop, etc.  Tom graciously took the idea and ran with it, coming up with something far more sophisticated than I had envisioned.  But the chip is still capable of doing one cycle, on demand.

Your drawn circuit seems to treat the two as separate entities that have to be selected between.  That's not "wrong", but consider some of the possibilities of the One Shot driving the Stomp LFO (e.g., the PDM Out of the One Shot feeding the Freq of the StompLFO instead of the 3.3V source), and see if that appeals to you.  Alternatively, the square wave of the Stomp LFO could be used to repeatedly trigger the One Shot and elicit modulation that trails/fades out.  For instance, the One Shot gets set for three repeats of a descending log-wave, that the Stomp LFO retriggers in a repetitive way, such that the final output produces rhythmic "triplets" of whatever effect one is controlling.

[Baran Ismen]

My original idea that I pitched to Tom for the One Shot, was for something that would/could be used to modulate modulation.  Hit the momentary switch, and the One Shot could make an LFO speed up, slow down, or progress from the one to the other and back again, or rise, rise, and rise then stop, etc.  Tom graciously took the idea and ran with it, coming up with something far more sophisticated than I had envisioned.  But the chip is still capable of doing one cycle, on demand.

Your drawn circuit seems to treat the two as separate entities that have to be selected between.  That's not "wrong", but consider some of the possibilities of the One Shot driving the Stomp LFO (e.g., the PDM Out of the One Shot feeding the Freq of the StompLFO instead of the 3.3V source), and see if that appeals to you.  Alternatively, the square wave of the Stomp LFO could be used to repeatedly trigger the One Shot and elicit modulation that trails/fades out.  For instance, the One Shot gets set for three repeats of a descending log-wave, that the Stomp LFO retriggers in a repetitive way, such that the final output produces rhythmic "triplets" of whatever effect one is controlling.

What you've suggested is truly great and sophisticated. For now, I wanted to keep everything simple. StompLFO circuit I've prepared can also be used with OneShot as it is. What you suggest is something one step ahead indeed, but a great idea. For now, I only have a wah pedal that has an expression input. I plan to get a Behringer US600 for some weird pitch modulation as well 

[Matthew Sanford]

I like your take on doing the StompLFO this way. You might consider adding switching from the OneShot's pin 3 to feed the Stomp's CV pins to institute Mark's idea internally, perhaps DPDT to switch from the pots since it gets persnickety when floating.