Logical Steps - patchable CMOS logic sequencer

[Ruebezahl]

The idea is based on some instructions in the genius “Logic Noise Series” on hackaday, written by Elliot Williams, which i can wholeheartedly recommend. In particular this article: “The switching Sequencer has the beat”
https://hackaday.com/2015/02/23/logic-noise-the-switching-sequencer/


Although i had a first breadboarded version done almost immediately, the whole process until everything was boxed and free of errors took me quite long, since i used some new techniques and learned a new program from scratch, called Inkscape (an open source vector graphic program), to design the layout.

So a bit more details about this machine, both inside and outside: <Logical> is an 8 step sequencer that can be controlled through patching and the behaviour can range from straight 1-2-3-4 to really funky polyrythms, all the way to really chaotic chaos. At the core is the idea of this article by Elliot Williams, that is based on several CMOS logic chips. At the heart is a 4051 8 channel (de-) mutliplexer that is controlling the feedback in an oscillator run on a 4093 NAND-Gate, thus working as a kind of non-linear sequencer. The remaining three Nand Gates are used to set up three independent oscillators, which can be directly listened to or used to control the three logic inputs A, B, C of the 4051, that determine which of the 8 potentiometers is controlling the main oscillator at each time. For a much better description of this concept please refer to the article by Elliot WIlliams i linked up there. For further variation and less chaotic control of the sequencer there is a 4040 Divider, plus an AND and an OR gate, as well as two envelope generators, also based on an idea by Elliot Williams. The whole machine is patchable through those connectors (i actually don’t know how they are called) that are ring and fork shaped and come in different colors, and alligator clips. A ring shaped connector is an input, a fork shaped connector is an output. There is also a mixing section with two tracks and a built in filter, based on a 4069UBE. The layout of the box is based on the case of a DVD package for learning Indonesian. It’s a very sturdy but light box, and the cool thing is that the inlet can be taken out and be replaced with whatever design you print on a paper, and it is protected by the outer foil.

Video: https://www.youtube.com/watch?v=bn-p-8l22es









Problems i came across:
- To my surprise, the dvd case was almost completely out of thick cardboard, which was almost impossible to drill, so i ended up with some really ugly holes and had to buy some special tools to hammer the holes into the case.

-After i already decided to use those kind of connectors (they are usually not used on user interfaces) i realized that i have to solder them after they are already in the case, which was a little bit of a challenge. And also I had to hotglue them to the case, because unlike banana jacks or 3,5” jacks, they don’t have any screws, which would make it much harder to repair later on.

-I used a vector graphic program for the first time, Inkscape, which i like a lot. Upon printing i realized that it doesn’t really support CMYK though (Actually i did not know about the problem with printing RGB at all). In the end i just printed it with RGB anyway and it came out okay, but i wasted a lot of time trying to solve this problem

- There were some problems in the circuit too, but since it is mostly based on already existing designs and i mostly just tweaked with some values or made minor changes, they were solvable. Mostly it was questions how the different parts would work together, and the filter was a bit freestyle, mixed together from several filter schematics i found online. I think most errors were rather my soldering mistakes or due to faulty parts.

-In general the layout was the most tricky part for me, because i had to fit all these functions in this limited space. I ended up not be able to use the jack output where i intended it to be, because it was too close to the potentiometer above it. Unfortunately when i realized it it was already too late, because all the connectors were already hotglued inside. So that's why you see a red hole where it is written OUT, and there is a jack with no designation. But it could be worse, and eventually everything is more or less working at least.

[Ruebezahl]

Here are the schematics, without any guarantee. I mean i built it and it works, but it's very possible there are some errors in the schematic, and i actually built it a bit different If you are a beginner and want to attempt something like this, i recommend just reading the original article on hackaday, and perhaps go through the whole series, it is really worthwile!

---

final schematic 1.png
Description:
Filesize:	129.84 KB
Viewed:	675 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

---

---

final schematic 2.png
Description:
Filesize:	61.39 KB
Viewed:	521 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

---

[Steveg]

It looks good and has a good array of sounds!

[hexagon5un]

[Ruebezahl]

[wakyct]

I think the panel design looks really good, nice job! And thanks for pointing out those articles.

[Ruebezahl]

Thank you! Actually i just realized when you click the thumbnails they lead you to other thumbnails, instead of the big pictures. I fixed that, so now you should be able to properly see the frontplate (and where i messed up )

[PHOBoS]

Nice clean layout and I love the colorful front.
You get some nice sounds out of it too.

I am most intrigued by your blue alligator cables. I have only been able to get sets with white/black/red/yellow/green.

[Ruebezahl]

[PHOBoS]

[NOISEBOB]

alligator clips are great!

[Ruebezahl]

[Ruebezahl]

Ah, i also came up with a circuit to sync this sequencer with LSDJ. LSDJ needs short 5V pulses (15ms), as opposed to the 9V pulsewaves the CMOS chips put out. So i had to see how to lover the pulse to 5V and also if i need to make it shorter. I tried a lot with Voltage Divider, which didn't work at all. As soon as i turned on the gameboy, a clean pulse (between 0V and 3V, 5V, 4.5V or whatever) turned into a pulse that never really goes back to 0, oscillating between for example 0,3V and 3V or 0,6V and 5V, which didn’t really work anymore to trigger the clock of the gameboy. Seems like some resistance at the gameboy input seems to influence the voltage divider.

So i decided, since i still had to test if i can trigger the gameboy with pulsewaves instead of short triggers, to try something i can do with parts i have lying around. I created a clock from a 40106 schmitt trigger, but this time running the chip from the gameboy power supply's 5V. So i have a clean 5V pulsewave, that didn’t get compromised by the gameboys input. But it still didn’t properly keep the gameboy in sync, so i searched for a way to transform this pulse in a trigger of a certain length. I found a really simple solution by Ray Wilson (MFOS), which only consists of a resistor, capacitor and a schmitt trigger. So with the same chip i could build this gate to trigger converter. And after playing around with some values, i settled for a 0,1uF cap and a resistor of 50k (it worked down until 23k, but let’s play it safe). If the resistor is bigger it still worked (i checked until 500k), but the short pulse actually becomes a short oscillation (probably due to the simplicity of the design), so i sticked with 50k. I checked the length of the pulse and it is only around 5ms, much less than the 15ms of the volca series. So it seems LSDJ is not THAT picky after all

So this problem is solved, and it’s good to know the gameboy can actually power a chip through the link cable. But of course i won’t power my whole machine through the gameboy in the end, also because it runs on 9V. So i thought a feasible solution would be run a 40106 from the gameboy’s 5V, and feeding it a 9V pulse from my sequencer. Since the power supply of the chip is 5V it should give out a pulse of 5V instead, which i’d turn into a 5V trigger with the next inverter. It’s not the most economic version, and takes quite some space, and i still have 4 schmitt triggers left, but i could pull it off with parts i have lying around. And, yippieh, it works! (at least on the breadboard with a mockup sequencer clock, i yet have to connect it to my actual sequencer!)

Perhaps i could try a similar version with a transistor later. I could also imagine using the remaining inverters to do the opposite version, so i can have an clk in and clk out with one chip, but for that i would have to use a 4069 and power it from the 9v instead i guess...

---

9v to 5v converter.png
Description:
Filesize:	9.85 KB
Viewed:	189 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

---

[Ruebezahl]

Oh, btw, after working on a tune with LSDJ and this machine and connecting them through the circuit i just showed here, i realized that the sequencer is going quite a bit slower when i connect it to the gameboy. as soon as i take out the cable, it's getting quicker again. We are talking about 20BPM give or take, quite a bit. It doesn't bother me too much at this moment, but i wonder why, and if i could fix it. I figure it is connected to the two power supplies somehow messing with each other, but not sure how to fix that. Input/output capacitors?

[kanebri]

Fantastic job!

I really like the enveloping and filtering on it. I sometimes get tired of sequencers since repetition isn't really my musical thing. (To each their own.) I think the variations and longer durations due to the filters and envelopes make a big difference. A lot of nice sounds in a little box!

[Ruebezahl]

Thank you! Of course while playing with it, i mostly see the places where i could improve this machine, so it is good to hear that, and remind myself, that it's already quite some possibillities for such a small machine