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 Forum index » DIY Hardware and Software » Musical Interfaces
SynthBend Controller System
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The Peasant



Joined: Nov 13, 2009
Posts: 90
Location: Sunny Alberta
Audio files: 1

PostPosted: Mon Feb 18, 2013 6:17 pm    Post subject: SynthBend Controller System Reply with quote  Mark this post and the followings unread

I am currently building a large synthesizer controller system which will include a very full featured volt/octave keyboard, an upgraded appendage ribbon controller module, and a wealth of other modulation controls. Force Sensitive Resistors are also being incorporated into a number of the modules. Details can be found here:

http://www.electronicpeasant.com/projects/synthbend/synthbend.html

Take care,
Doug

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elmegil



Joined: Mar 20, 2012
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PostPosted: Mon Feb 18, 2013 6:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

138 banana jacks.

Awesome work Smile
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Benjamin AM



Joined: Nov 04, 2010
Posts: 57
Location: Boise

PostPosted: Wed Feb 20, 2013 7:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice work!

I've been throwing around the idea of installing an FSR circuit underneath my appendage controller. I was curious if you have built and tested the circuit that you have drawn up on your website. My main concern is that that there may be a "dead spot" or area of dulled response in the middle of the controller. This concern arises because I noticed that there are only two small sensors for the length of your keyboard. I've never experimented with these FSR sensors so I am unsure if this is a legitimate concern. With that said, I am sure that there is an easy way to compensate for a sensitivity droop if this problem does exist. Although, I haven't spent much time trying to derive meaning from the schematic, I would assume you have done this. I can't wait to try this out. Have any suggestion to which sensor to purchase?
-Ben
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The Peasant



Joined: Nov 13, 2009
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PostPosted: Wed Feb 20, 2013 9:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Benjamin AM wrote:
Nice work!

I've been throwing around the idea of installing an FSR circuit underneath my appendage controller. I was curious if you have built and tested the circuit that you have drawn up on your website. My main concern is that that there may be a "dead spot" or area of dulled response in the middle of the controller. This concern arises because I noticed that there are only two small sensors for the length of your keyboard. I've never experimented with these FSR sensors so I am unsure if this is a legitimate concern. With that said, I am sure that there is an easy way to compensate for a sensitivity droop if this problem does exist. Although, I haven't spent much time trying to derive meaning from the schematic, I would assume you have done this. I can't wait to try this out. Have any suggestion to which sensor to purchase?
-Ben


Hi Ben,

The circuit on my website has been breadboarded and works well, but it does not need to compensate for any "droop" caused by mechanical issues. The keyboard that I am using is fairly small, and there is a ridgid metal bar installed underneath it that ensures that wherever the keyboard is pressed the sensors will activate correctly. This metal bar is visible in the posted pictures. This arrangement has been tested and works just fine.

If you plan on putting a FSR sensor directly underneath your appendage softpot ribbon then you should probably use the FSR 408 ribbon which is a long, narrow ribbon that can be trimmed to the same length as the softpot ribbon. If you have already built your appendage and the ribbon is currently attached to a ridgid surface that you want to place the FSRs underneath, then I would experiment with FSR placement to get good results wherever the ribbon is pressed. Probably three or four FSR 402s spaced evenly along the base of your ribbon mount would be fine, depending on how stiff it is. All of the FSRs can then be wired in parallel and connected to the posted circuit. Alternatively, the FSR 408 ribbon could be used here as well, but how well it works will depend on your particular physical arrangement.

Take care,
Doug

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tojpeters



Joined: Feb 04, 2013
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Location: cali (far north)

PostPosted: Sun Feb 24, 2013 8:44 am    Post subject: very striking design Reply with quote  Mark this post and the followings unread

did you know what you were going to do with those plastic cases as soon as you saw them or did they sit around gathering dust a long time before inspiration hit you? Do you mind if i borrow heavily from your frs circuit? I want to basically build 2 of the ones that have cv and gate and add a selector for gate buss 1 or 2 to both of them along with a manual gate button that also can be routed to either or both busses. I'm thinking of adding 2 op amp mixers to combine the signals and send them to the 2 LM311. Once again very nice work.
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The Peasant



Joined: Nov 13, 2009
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PostPosted: Sun Feb 24, 2013 11:26 am    Post subject: Re: very striking design Reply with quote  Mark this post and the followings unread

tojpeters wrote:
did you know what you were going to do with those plastic cases as soon as you saw them or did they sit around gathering dust a long time before inspiration hit you? Do you mind if i borrow heavily from your frs circuit? I want to basically build 2 of the ones that have cv and gate and add a selector for gate buss 1 or 2 to both of them along with a manual gate button that also can be routed to either or both busses. I'm thinking of adding 2 op amp mixers to combine the signals and send them to the 2 LM311. Once again very nice work.


The cases had sat around for years before I found this use for them. I had no idea at all what I was going to do with them when I first started collecting them.

Please feel free to use the FSR circuit however you would like, that is the reason why I posted it. Thank you for the nice comments!

Take care,
Doug

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tojpeters



Joined: Feb 04, 2013
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PostPosted: Sun Feb 24, 2013 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Do you think this would work to select gate busses, or am I overcomplicating things ? I hope you can see where this inserts into your circuit. Should I leave out the extra op amp and just connect the switches to the LM311s? Thanks for any input you have.


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The Peasant



Joined: Nov 13, 2009
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PostPosted: Mon Feb 25, 2013 12:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

tojpeters wrote:
Do you think this would work to select gate busses, or am I overcomplicating things ? I hope you can see where this inserts into your circuit. Should I leave out the extra op amp and just connect the switches to the LM311s? Thanks for any input you have.


In general it looks like your circuit should work, however there are a few errors in it that would have to be corrected. The diodes coming from the FSRs are connected to the positive op amp input instead of the negative, the LM311 positive and negative inputs have been reversed, and the op amps connected just before the LM311s are wired as comparators themselves, they should have a 100K feedback resistor from output to negative input to act as invertors as intended. You can simplify the circuit a bit by omitting the final op amp stages entirely and wiring the LM311 inputs backwards (as they are actually shown here.)

As well, with your manual gates wired the way that you show them, their operation will depend on the gate level setting, which you may not want. You may want to consider doing all of your gate bus mixing after the LM311s instead of before, depending on how you want the circuit to function.

Take care,
Doug

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The Peasant



Joined: Nov 13, 2009
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PostPosted: Mon Feb 25, 2013 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, and the bottom connection from the far left manual trigger should be connected to the input of the next op amp stage, not to the output of the FSR op amp.

Take care,
Doug

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The Electronic Peasant

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tojpeters



Joined: Feb 04, 2013
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Location: cali (far north)

PostPosted: Mon Feb 25, 2013 2:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for looking, and correcting the numerous faults. Just to be clear this is what i hope to achieve. I assign FSR1 and FSR2 to gate buss 1. I press FSR1 and adjust gate level to 10V. Now I can press FSR1,FSR2, and manual gate 1 all at the same time,or any one of them alone and get a 10V gate signal. I think I'll redraw it with a TL072 and wiring the inputs to the LM311 "backwards".
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The Peasant



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PostPosted: Mon Feb 25, 2013 2:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

tojpeters wrote:
Thanks for looking, and correcting the numerous faults. Just to be clear this is what i hope to achieve. I assign FSR1 and FSR2 to gate buss 1. I press FSR1 and adjust gate level to 10V. Now I can press FSR1,FSR2, and manual gate 1 all at the same time,or any one of them alone and get a 10V gate signal. I think I'll redraw it with a TL072 and wiring the inputs to the LM311 "backwards".


You may be misunderstanding what the "gate level" control does. It sets how hard that you have to press on the FSR before a gate is generated. It does not set the actual voltage of the gate output, which remains a bit above 10 volts any time that an actual gate is generated.

Other than that, it should work as you say above.

Take care,
Doug

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tojpeters



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PostPosted: Tue Feb 26, 2013 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

I did misunderstand the gate level. Here are the {hopefully} corrected schematics if you could give them a look please.


fsr gate buss2.pdf
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The Peasant



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PostPosted: Tue Feb 26, 2013 9:15 am    Post subject: Reply with quote  Mark this post and the followings unread

tojpeters wrote:
I did misunderstand the gate level. Here are the {hopefully} corrected schematics if you could give them a look please.


Everything looks OK except that you still need to correct the top manual gate connection to the bottom circuit. The 100K resistor should connect directly to pin 6 of the TL072 instead of to the output of the FSR op amp.

Take care,
Doug

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tojpeters



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PostPosted: Tue Feb 26, 2013 11:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks. i'm really excited about this circuit. I'll be ordering the bits I need soon.
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tojpeters



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PostPosted: Wed May 15, 2013 8:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Really looking good. And sounding good,I watched the youtube video
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The Peasant



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PostPosted: Sun Feb 09, 2014 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

After a year and a half, this project has finally been completed!

http://www.electronicpeasant.com/projects/synthbend/synthbend.html

Take care,
Doug


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The Electronic Peasant

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Blue Hell
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PostPosted: Sun Feb 09, 2014 12:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great build Doug, and those synths look amazing too!
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sneakthief



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PostPosted: Sun Feb 09, 2014 12:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's an inspired project! I like how it interfaces with the rest of the modules.

ps. greetings from Berlin from a fellow Albertan Smile

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The Peasant



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PostPosted: Mon Feb 10, 2014 10:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank you for the nice comments!

This controller is really a lot of fun. I hope to do a video of the whole thing in use soon, I will definitely post it here.

Greetings to you too Sneakthief! Was -31C this morning, you are probably not missing that!

Take care,
Doug

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inlifeindeath



Joined: Apr 02, 2010
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PostPosted: Sat Feb 15, 2014 2:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Lovely build as always E. Peasant!
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BobTheDog



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PostPosted: Mon Feb 24, 2014 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very impressive stuff, nice job!
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tojpeters



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PostPosted: Thu Feb 27, 2014 2:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Really nice. I did use one of your FSR schematics as drawn on my Martenot controller. Works great!
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