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Constant Time Slide Control
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Grumble



Joined: Nov 23, 2015
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PostPosted: Mon Dec 11, 2017 3:11 am    Post subject: Constant Time Slide Control
Subject description: Looking for a circuit diagram
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Hi all,

I am building a sequencer based on the idea of the M185 sequencer made by RYK but based on an Arduino (see: https://youtu.be/QPUI9k5kWKM and http://electro-music.com/forum/topic-69406.html )

For this project I need a Constant Time Slide Control.
A simple a slide or glide diagram is made where the charge current into a capacitor is set by means of a potentiometer so the time it takes to charge the capacitor to a certain voltage depends on the voltage difference between two steps.
Larger voltage step means longer charge time (longer glide) aka constant rate style portamento.
What I am looking for is a circuit where the charge (or glide/slide) time is set by the potentiometer and is constant for all steps, this is called a Constant Time Slide Control.

Maybe someone is willing to think with me and/or point me in the right direction?

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Blue Hell
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Joined: Apr 03, 2004
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Location: The Netherlands, Enschede
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PostPosted: Mon Dec 11, 2017 3:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok, some ideas ...

In hardware or in software?

In hardware ... you'd need to look a step ahead to determine the voltage difference and control a current from that.

Interpolation between steps would be easier in software as you'd have to know about the step values upfront anyway. I hardware you would need a separate "look ahead" sequencer it seems.

Also .. what should happen when you fiddle the step values while the sequencer runs?

Will the sequencer always run forwards one step at a time, or can it skip steps or move backwards?

Another option would be to remember the previous step and then when a new step comes in you'd have two values you could control a current from ... but the sequencer would be one step behind then.

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Grumble



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PostPosted: Mon Dec 11, 2017 3:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Hardware Cool (no place left for software and the accompanying ports to control this).
The direction is not relevant since there will only be an analog voltage in steps of different amplitude representing the positions of the ( 8 ) potentiometers.
I guess there will be some kind of sample/hold device needed (like you suggest in your post) that holds the last step and then the current into the glide capacitor must be made dependent of the amplitude difference of the next step...
The glide will be at the beginning of each step, but there's where it should be, because that is where the gate starts.

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Grumble



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PostPosted: Mon Dec 11, 2017 4:10 am    Post subject: Reply with quote  Mark this post and the followings unread

What was I thinking? The RC network IS exponential...
Guess I had my info mixed up..

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Blue Hell
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PostPosted: Mon Dec 11, 2017 5:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Shocked

I thought you wanted linear Laughing

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Grumble



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PostPosted: Mon Dec 11, 2017 5:08 am    Post subject: Reply with quote  Mark this post and the followings unread

No Wink but thanks I'm sorry
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