The 4023 PWM Oscillator, Obsession and Me

RingMad

Where does one stop!?

Last month I got obsessed with the CD4023 Pulse Width Oscillator that Rykhaard / Richarius had posted over on The Sound of Logic / Deathlehem forum. I found messages here mentioning it, but I could not find the schematic itself here.

So I built it and really loved it. Then, instead of working on my long-overdue suitcase synth, I became obsessed with automatizing several things with this circuit (which is now destined for said suitcase synth!)...

Then I ran it through my favorite triangle waveshaper (the 4015 & 4011, as found in this thread: http://electro-music.com/forum/topic-52443.html ).

Then I added the CV part to it, as devised by Rykhaard. Despite not being able to get the full range, it was still a lot of fun. I'd take the output of a 4-bit random generator into an R/2R and use that as a CV. Fun.

Then, wanting to replace the rotary switch that selects the capacitor in the circuit, I used a 4051 with 3 switches to choose 1 of 8 caps. But then of course, when one has an electronic switch, one can make that automatic. So 3 oscillators feed that, switching the cap. Crazy. Fun.

Then I eyed the feedback pot in the circuit. To replace it, I generate a voltage using a 4-bit random gen into an 2/2R. The resulting voltage feeds an LED in a home-rolled opto-isolator (AKA Vactrol), and the resulting resistance from the LDR is used instead of the pot. Crazy. Fun.

With all these things going at once, the sounds are pretty crazy. I tried adding slew/portamento/glide to one of the random CV's, but with all the cap-switching, it wasn't noticeable.

Almost all my breadboards are used, and they are sprawling all over the place.

And I want to further the self-playing ever-changing automaticness of this beast. I have some ideas, but I need a triangular VLFO, very slow, like 1 cycle per hour or maybe even 1 cycle per 17 minutes or something. I've had no luck with the old 4069 or LM324 LFO circuits. I have been racking my brain trying to figure out how to get a 4029 to count up then down all by itself. Anyway, that's possibly another thread.

There are 4 sound snippets posted on my soundcloud... (CMOSnippets #36 thru 39)... http://soundcloud.com/jamesschid .

This is a video of the earlier incarnation, with the CV input driven by a 4bit random generator into an R/2R : http://www.youtube.com/watch?v=JWXbtgKunJY . There's also a 4046 VCO following the same random voltage.

And I just shot a new video showing the last version, with the cap-switching and replaced feedback pot... http://www.youtube.com/watch?v=nJKgY3oQKI8 .

James.

jcintheus · Joined: Oct 16, 2011 Posts: 53 Location: Colorado

I've also had alot of fun with this circuit! I made mine out of a 4093 and some mml. (I see you've seen)
As far as drawing a line, if you're really asking, who needs a line?
It looks like you cold develop quite a few different modules based on the same circuit.
Just keep notes! Smile

JingleJoe · Posted: Fri Oct 05, 2012 12:51 am Post subject:

In answer to your first question:
One does not stop, one gets more shelves and more space and more parts and continues building the robots.

Carry on the good work and get something soldered up so you have some breadboard space again Laughing

remember to do a circuit diagram first.

RingMad · Posted: Fri Oct 05, 2012 4:25 am Post subject:

elmegil · Posted: Fri Oct 05, 2012 5:45 am Post subject:

Any chance you can share that circuit from Deathlehem?

I have had nothing but bad luck with that site; first it took weeks to get approved, and then after finally being able to log in, now my account is no longer active or recognized.

I'm not upset with the owner or anything, I am just frustrated that it has been so difficult to work with the site.

RingMad · Posted: Fri Oct 05, 2012 12:22 pm Post subject:

elmegil · Posted: Fri Oct 05, 2012 12:45 pm Post subject:

Thanks

I'll give it another shot.

analog_backlash · Posted: Tue Oct 09, 2012 2:45 pm Post subject:

I find that no matter how many breadboards I have, I still manage to end up with them full of circuits. There must be some kind of law here - you can never have enough breadboard space. At the moment I have the randomizer, an experimental lunetta mixer, a slow-clocked white noise generator test circuit and a multi-synth mixer prototype all on the go. The answer is to commit them to PCB (or perfboard). The trouble is, I'm only 100% happy with the randomizer (I think). I think I'll do something about that tomorrow (although I always say that). Now, of course, I'd like to try out this 4023 circuit as well as hundreds more circuits that I've seen. I think that this website can only lead to madness (although I'm already there Evil or Very Mad

).

Keep up the good work,

Gary

RingMad · Posted: Wed Oct 10, 2012 5:18 am Post subject:

Committing to PCB/perfboard is tough for me. I want to make absolutely sure that I am 100% happy with the circuit, that the cap values and pot ranges are the most useful, etc. When I build a box, I usually still have the actual circuit still on the breadboards in case. And despite my careful planning, I still sometimes make changes to the box afterwards.

As for having a pile of circuits to try, well, yeah, this site certainly has a wealth of great ideas. It can be overwhelming as one's list gets longer and longer. I figure it's better to have lots of ideas than no ideas.

James.

analog_backlash · Posted: Wed Oct 10, 2012 5:46 am Post subject:

I also keep a breadboarded version on standby until I'm 100% happy with the hard-wired version. This is because, although I have a circuit diagram, I sometimes make small changes and forget to update the drawing/printout. Secondly, you can compare the performance of the 'properly' built one against the breadboard example (I have found the odd mistake at this stage). I once had a sample and hold circuit which worked perfectly well on the breadboard, but leaked alarmingly on PCB. It turned out that it was due to two tracks running close and parallel to each other. When I amended this, it worked. I think that it was down to the two tracks acting as a capacitor (but I'm still not totally sure).

As for the number of ideas, I'm glad that there are so many here. It's which one to try next that's my problem...

Cheers,

Gary