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 Forum index » DIY Hardware and Software
Voltage Control of Sequencer Step Count?
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elmegil



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PostPosted: Wed Sep 05, 2012 5:30 am    Post subject: Voltage Control of Sequencer Step Count? Reply with quote  Mark this post and the followings unread

I had an interesting idea in the shower this morning, which seems like it ought to be obvious, but quick googling doesn't show any sign of.

The base idea is voltage control of the number of steps in a step sequencer (e.g. Baby10). Originally was thinking about how I could replace an 8 way rotary switch with a pot.

First question before I expose my naivete Smile is what sequencers out there (whose schems I could look at) use voltage control for the number of steps? I know there are voltage controls for lots of other aspects....

The only hit I get in google is Fonik's VCPS but I thought that the voltage control was over the pattern, not the step count?
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JingleJoe



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PostPosted: Wed Sep 05, 2012 9:01 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm sure one of Ray Wilson's did this. If I remember rightly he used it to control step length, I think I have the basic idea clarified:
He used the standard analogue to digital voltage sensor, like a very simple digital voltmeter; a quick google will yeild more detailed results pertaining to what you want to do Smile
One would use the binary output of the counter portion of that circuit to pre-set another counter, which after so many steps sends a pulse to the reset of the sequencer counter IC.

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marvkaye



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PostPosted: Wed Sep 05, 2012 9:56 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
I'm sure one of Ray Wilson's did this. If I remember rightly he used it to control step length, I think I have the basic idea clarified:
He used the standard analogue to digital voltage sensor, like a very simple digital voltmeter; a quick google will yeild more detailed results pertaining to what you want to do Smile
One would use the binary output of the counter portion of that circuit to pre-set another counter, which after so many steps sends a pulse to the reset of the sequencer counter IC.


Sounds like part of Ray's "multi-function module".
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JingleJoe



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PostPosted: Wed Sep 05, 2012 2:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

http://www.musicfromouterspace.com/analogsynth_new/SEQUENCER_VARICLOCK/SEQUENCER_VARICLOCK.php
This is what I was talking about Smile found it!

However this is another case of the Ray Wilson description Rolling Eyes
[IMPENETRABLE WALL OF TEXT]
[CONFUSING NON-LINEAR DIAGRAM]
Maybe it's just me but that's how I allways see his descriptions.

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Thomas_Henry



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PostPosted: Wed Sep 05, 2012 2:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi gang,

Have you seen my Superseque from several decades ago?

http://machines.hyperreal.org/categories/DIY/sequencer/supseq.pdf

There is a "length" input that can be used for this. If I were doing it, I would use a Picaxe 18M2 as a one-chip solution. It has an ADC input that can sense the voltage and plenty of inputs/outputs to select up to a length of 16. Another messier possibility is to simply use a CMOS decoder with a few external gates.

Thomas Henry
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elmegil



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PostPosted: Wed Sep 05, 2012 2:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Actually, no I hadn't seen that. I'll give it a look, thank you Thomas Smile

And thanks for the MFOS links as well guys...

What my idea was, was to take the individual outputs of the 4017 into a voltage divider (probably less complex than an R/2R network, since only a single step/stage would be active at any given time, unlike a counter/DAC input) and calibrate that such that the voltage would be proportional to the current step number. Then take a pot divider and that step voltage into a comparator to generate a reset pulse at the appropriate step. At which point it was obvious I could use a CV input to do the same thing as the pot divider.
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Dave Kendall



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PostPosted: Fri Sep 07, 2012 12:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's an idea using CMOS.

Send the step number CV into a LM3914 LED bargraph driver in "dot" mode, and feed the lower 8 of its outputs into a 4532 priority encoder's inputs. The 4532's 3-bit outputs then switch a 4051. This in turn selects which of the 4017's Q outputs is fed back into the 4017 RESET (pin 15), thus determining the number of steps.

There is a very slight (approx 1mV according to the datasheet) overlap between successive outputs from the 3914 in dot mode, which probably wouldn't be a problem.
Some dicking around with the voltage reference for the 3914 would be needed, but that lets you scale the incoming CV for step number, which is probably desirable anyway.

It's an untested idea I once had for selecting the initial division of the midi2clock via voltage control.........


cheers,
Dave

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diablojoy



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PostPosted: Fri Sep 07, 2012 12:49 am    Post subject: Reply with quote  Mark this post and the followings unread

CV in to window comparators to CMOS switches to select a reset point
1-8 steps = 2 x LM339 plus 2 x CD4066 and a few resistors
1-16 steps would of course be double that plus maybe a buffer and cv disto
but might be worth looking into.
of course you could just use a voltage controlled divider to send a reset when you wanted and sequence the cv into that to vary the number of steps that are played before resetting . the CGS one is good.

edit : the Higgs Captain would be off with the
Higgs cabin boy
[her name was Mr prostitute if i recall correctly]

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bubzy



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PostPosted: Fri Sep 07, 2012 4:22 am    Post subject: Reply with quote  Mark this post and the followings unread

+1 for the lm3914
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fonik



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PostPosted: Fri Sep 07, 2012 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

yep. with the bargraph driver you have several windows comparators, actually...
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diablojoy



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PostPosted: Fri Sep 07, 2012 10:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
yep. with the bargraph driver you have several windows comparators, actually...


10 comparators yes.. but unfortuanately they are not window comparators .
as they do not provide for both lower and upper voltage limits for each individual comparator
so multiple outputs will turn on as input voltage rises.
this means more circuitry is required next to resolve a single output
to provide a single reset only at step 'n'
hence Dave's use of a 4532 and 4051 to select only one Q output of the 4017 for sending to the reset pin. I must admit would like to see a scheme for that Dave, sounds interesting and its giving me some other idea's already.

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fonik



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PostPosted: Sat Sep 08, 2012 1:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
Quote:
yep. with the bargraph driver you have several windows comparators, actually...


10 comparators yes.. but unfortuanately they are not window comparators .

in dot mode they work like window comparators, would think? not that they ar windo comparators, however, only one output is ON, depending on the voltage, so the result is like they where window comparators.

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diablojoy



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PostPosted: Sun Sep 09, 2012 2:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
in dot mode they work like window comparators, would think? not that they ar windo comparators, however, only one output is ON, depending on the voltage, so the result is like they where window comparators.

Damn really ? oh well wouldnt be the first time i was wrong
So in dot mode they work like 10 window comparators , thats awesome !
lots of uses spring to mind
but if that is the case then you would only then require a couple of cmos switches
there would be no need of a 4532 and 4051
you could use the outputs to directly drive the logic pins on a pair of 4016 or 4066 to select which of the 8 x Q outputs of the 4017 is to be used for reset.
or am i missing something ?

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fonik



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PostPosted: Sun Sep 09, 2012 5:18 am    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
you could use the outputs to directly drive the logic pins on a pair of 4016 or 4066 to select which of the 8 x Q outputs of the 4017 is to be used for reset.
or am i missing something ?

yes. you would need inverters, i think, since the outputs of the bargraph driver are drains, actually.

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ryktnk



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PostPosted: Sun Sep 09, 2012 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello

How about the M185 !!
http://electro-music.com/forum/topic-27157.html

Each stage has voltage control of length of steps and type of steps.

Although I have been lazy to update the project, sorry . . .

-ryk
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diablojoy



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PostPosted: Sun Sep 09, 2012 2:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
the outputs of the bargraph driver are drains,


ah of course i should have picked that from the data sheet, thanks matthias .
off topic this chip may be what i have been looking for.
I have another project in mind.

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fonik



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PostPosted: Mon Sep 10, 2012 1:03 am    Post subject: Reply with quote  Mark this post and the followings unread

is the 3914/15 still in production? mayeb this would be a good starting point for a CV adressable switch. will have a look into that.
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zthee



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PostPosted: Mon Sep 10, 2012 1:46 am    Post subject: Reply with quote  Mark this post and the followings unread

You could use a LM3914 to drive a CD4532. Then you get a 3-bit binary code out of the incoming voltage. Hook up a CD4051 or something, and you'll get a simple sequencer.
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diablojoy



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PostPosted: Mon Sep 10, 2012 2:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
mayeb this would be a good starting point for a CV adressable switch. will have a look into that.

totally off topic now but my thoughts exactly
In fact i was thinking 4 CV addressable switches
to create an A,B,C,D matrix sequencer
where A selects octave , B selects semitone , C selects gate length and
D selects a choice of incoming CV sources summed with the output CV or a choice of trigger signal timing not fully decided on that one just yet as to which would be more useful.
Its something i have been wanting to do for a while , just hadn't considered trying this chip before. I was looking at LM339 comparators
so an LM3914 may shrink things some what.
Its one of the idea's driving the change to my octave and semitone switching board by the way. i knew i would need to shrink the panel space required , overall it would not be a small project
still at the moment it is nothing but a bunch of very loosely connected idea's.

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diablojoy



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PostPosted: Mon Sep 10, 2012 2:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
is the 3914/15 still in production?

at end of life status i believe
however both futulec and element 14 have them in stock
for the moment.

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fonik



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PostPosted: Mon Sep 10, 2012 3:07 am    Post subject: Reply with quote  Mark this post and the followings unread

still in production (National/TI).

BTW this is straight on topic, i believe, since a CV adressable switch is exactly what was asked for in the OP. it is just the purpose that is different.

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elmegil



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PostPosted: Mon Sep 10, 2012 5:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Yep, that's a good call Smile
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diablojoy



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PostPosted: Mon Sep 10, 2012 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

yes good point
my purpose was off topic only.
so a CV addressable switch seems to be easily acheivable at this point
and upward scalable to boot to a large number of I/O's

the approx 1mV crossover point between adjoining outputs may prove somewhat of a challenge
Was thinking a sample and hold on the incoming CV may help to limit
the instances where it would occur clocked at the same rate as the sequencer in question though after some more thought on it
in fact for the original topic case it may prove worse
as there is a slim possibility of enabling and holding 2 reset points at once
however for a stand alone CV addressable switch some method of clocking is a basic need and it would provide a simple solution and for in my particular case some important added benifits
another possible solution for timing would be to add a single transistor NOT gate to the lm3914 outputs [required anyway] and then AND those outputs with a clock and then apply them to the logic pins of cmos or DG series switches.
neither removes the possibility of 2 outputs occuring completely but perhaps dave's idea was aimed at acheiving that , not sure havent looked properly into that one yet. still so much to learn.

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fonik



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PostPosted: Tue Sep 11, 2012 1:17 am    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
the approx 1mV crossover point between adjoining outputs may prove somewhat of a challenge
<snip>in fact for the original topic case it may prove worse
as there is a slim possibility of enabling and holding 2 reset points at once

for the original topic this won't be an issue. you could have two adjacent reset points, yes. but the sequencer would simply reset at the first. Cool

two reset points would be an issue if you wanted to visualize the reset, though.

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diablojoy



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PostPosted: Tue Sep 11, 2012 2:09 am    Post subject: Reply with quote  Mark this post and the followings unread

At least a couple of 4017 based sequencers that i know of dont tend to work well with 2 reset switches thrown at the same time i feared this may prove a similar case. It is admittedly an unlikely event to occur very often.
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