[sdiy] Two parameter mechanical controller thoughts....

Fri Jun 7 20:45:28 CEST 2019

Hi Pete,

I salvaged a bunch of great metal rods / slides from a broken inkjet printer.    

It might be a good source of parts?

Dave

From: Synth-diy <synth-diy-bounces at synth-diy.org> On Behalf Of Pete Hartman
Sent: Friday, June 7, 2019 2:40 PM
To: synth-diy at synth-diy.org DIY <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Two parameter mechanical controller thoughts....

I've been kind of stuck on pulleys having their axes perpendicular to the panel/pcb surface, but if they are parallel....  Ok.  That can replace the soft pot without taking up a lot of space, and makes some aspects of this simpler.  Still need a rail; those linear bearings at McMaster are spendy, but I haven't looked to see if there are less quality solutions that are "good enough" from elsewhere.  The idea of having 4 x 100mm controls on a module is a minimum $160 just for the hardware, not counting encoders, pulleys, etc. is kind of daunting for a DIY project.

Pete

On Fri, Jun 7, 2019 at 12:57 PM thresholdpeople <thresholdpeople at protonmail.com <mailto:thresholdpeople at protonmail.com> > wrote:

The Appendage is great. 

It's kind of a trade off in that the softpot takes up less space for sure, but then it needs all this other sort of support infrastructure to make the encoder right. Using a belt and pulley system would inherently provide the infrastructure, but it's bigger on the inside.

Watching the Collidoscope video the lever riding on the softpot looks kind of wobbly. Using a mechanism of some sort like a linear bearing or belt and pulley etc would create a much more robust hands on instrument. 

Another thought is that the mechanism is similar to the Ondes Martenot ring. Perhaps if approached from that perspective you can have something that's less obviously an encoder/knob on the top, and something built/disguised more into the slider mechanism. 

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Friday, June 7, 2019 1:39 PM, Pete Hartman <pete.hartman at gmail.com <mailto:pete.hartman at gmail.com> > wrote:

The Collidoscope itself is actually a lot simpler on the inside that it would appear from the videos.

It uses a Teensy to convert the encoder output and softpot position (and any other sensors) to midi messages.

It has MIDI from the keyboard and the Teensy going to a raspberry pi that displays the waveform on a large monitor.

It uses a FocusRite interface to handle audio in and out duties for the Pi.

The display monitor is mounted under the surface of the "table" with a divider down the middle.  The Pi does all the synthesis and display work.

I was kind of liking the softpot idea, because I have one already set up as the controller for an Appendage (check electro-music.com <http://electro-music.com>  for some of the details about the Appendage, it's a very feature-rich ribbon controller).

One advantage it has is that the belt/pulley idea requires that you have additional space to the side of the carriage for mounting the belt/pulley behind the panel.  The softpot, if mounted appropriately doesn't have to add more than ~8mm to the width of the overall mechanism, and depending on the details, could conceivably add zero.  I'd expect mounting an encoder and belt and pulleys for the belt to take up more than that.

Pete

On Fri, Jun 7, 2019 at 12:27 PM Ben Bradley <ben.pi.bradley at gmail.com <mailto:ben.pi.bradley at gmail.com> > wrote:

I remember the "Crazy Synthesizer Demo" from a few years ago, and just

looked at it again. From what I remembered, I thought it was just a

big touch-screen like an ipad, but I see it's a long slider with a

round knob.

There's also the ribbon controller like on the Micromoog, and I recall

seeing one that's substantially longer. That's not what you want, but

it's another idea.

I kind of like the belt/pulley idea. This could go to a

high-resolution rotary encoder, microcontroller and a high-resolution

DAC to generate a precise control voltage that feels "analog."

On Fri, Jun 7, 2019 at 1:13 PM Quincas Moreira <quincas at gmail.com <mailto:quincas at gmail.com> > wrote:

> 

> I think I'd lose the softpot too, and use some kind of belt/pulley to turn a rotary pot/encoder

> 

> On Fri, Jun 7, 2019 at 9:58 AM thresholdpeople via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org> > wrote:

>> 

>> The thing with CNC gantry systems like 3D printers is that most lower end ones use stepper motors for both the drive and positioning, so running them in reverse won't be possible to create a control voltage based on position with out a whole lot of extra circuitry. However they may often have parts like linear bearings, precision-ish shafts, and all sorts of other hardware that could be re-purposed.

>> 

>> 

>> 

>> Check out Author & Punisher - http://www.tristanshone.com/ - he makes awesome controllers, and has one or two that are as you're describing, Pete. He's pretty open about construction and functionality.

>> 

>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

>> On Friday, June 7, 2019 9:55 AM, Pete Hartman <pete.hartman at gmail.com <mailto:pete.hartman at gmail.com> > wrote:

>> 

>> 

>> 

>> On Fri, Jun 7, 2019 at 7:07 AM bbob <fluxmonk at gmail.com <mailto:fluxmonk at gmail.com> > wrote:

>>> 

>>> i'd go wireless - bluetooth or ble from whatever controls are on the carriage, and a time-of-flight sensor to measure the carriage position.  there's probably a lot of hardware bits you could repurpose from folks developing diy 3d printers for the carriage mechanics.

>>>> 

>>>> 

>> 

>> I'm not sure wireless would be practical for within-the-module communications in a Euro module or standalone controller meant to interface with Euro.....

>> 

>> 3D printer carriages would be a good source of inspiration though.

>> 

>> The linear bearings at McMaster look really interesting, I'll have to spend some time digging around in that stuff.

>> 

>> Thanks

>> 

>> Pete

>> 

>> 

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> 

> --

> Quincas Moreira

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