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Expression Pedal Range Issues

Building organ consoles for use with Hauptwerk, adding MIDI to existing consoles, obtaining parts, ...
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Clavecin

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Expression Pedal Range Issues

PostSun Jan 22, 2023 8:10 am

I've had a very nice (expensive) pair of expression pedals made for my Hauptwerk console conversion, which I've had running for about 6 months.

The problem I have is that the 2 pots only operate over about 30% of their full range and register in the region of 50 -100 in Hauptwerk. Hauptwerk then stretches this to 0 -127, but only gives 6 steps of expression from fully closed to fully open, which gives an unsatisfactory crescendo/diminuendo.

I could fit geared pots (I already have one from the console prior to conversion) but they are notoriously difficult to set up. Another alternative is linear sliding pots. Either option would be difficult to accommodate and I'd prefer not to have to do anymore console alterations.

Has anybody got experience of a MIDI encoder which can be programmed via software to upscale the output of expression pedal pots to the full 0 - 127, I've heard that some will do this but haven't found any references to a make/model yet. I'd be using this just for the expression pedals as the 'Tutti Encoder' I'm using for the entire organ works just fine.
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magnaton

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Re: Expression Pedal Range Issues

PostSun Jan 22, 2023 10:48 am

A MIDI range of 50 to 100 should suffice for HW to evenly divide the steps as I've done it with even less. Try autodetecting again with the expression shoe fully closed then fully open and back again. Also try moving the expression shoe on the sample set in question with the mouse then compare that with the newly autodetected swell shoe for comparison.

Danny B.
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GrahamH

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Re: Expression Pedal Range Issues

PostSun Jan 22, 2023 11:11 am

Regardless of whether your pots are rotary or slider they need to be linear for MIDI/Hauptwerk (not logarithmic which are used in amplifiers etc. as volume controllers).
Ideally the linkages to your expression pedals should be such that the pots operate over more or less their full range, so that from ‘swell box closed’ to ‘swell box open’ you get from 0 volts to approximately 5 volts going to your MIDI encoder which will then generate MIDI messages from 0 to approximately 127.
However, you might get away with only using 30% of the sweep. You’ll have to “suck it and see”.

To the best of my (somewhat limited) knowledge, it is your MIDI encoder (not Hauptwerk) that governs the number of steps from ‘box closed’ to ‘box open’.
When I programmed an Arduino Nano, and also an Arduino Pro-micro for use as a pedal board plus swell pedal encoder, I initially found that I was getting 127 single steps!! By changing one number in a line of code I was able to reduce this to a manageable number of steps.
Perhaps you could have your MIDI encoder re-programmed?

Graham
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larason2

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Re: Expression Pedal Range Issues

PostSun Jan 22, 2023 12:51 pm

The design I use for an expression pedal sensor is very adjustable, I would guess yours should be too. Can you post a picture of it? I agree, hopefully you have a linear pot in there, not a logarithmic one! You should hopefully be able to reprogram your encoder, but I think adjusting the pedal mechanism would be easier.
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Clavecin

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Re: Expression Pedal Range Issues

PostMon Jan 23, 2023 7:14 am

Thanks for the 3 replies, to follow up the suggestions:

1. The pots I am using are 10k linear rotary type, but without a 'rack-and-pinion' or 'geared' mechanism so only operate over about a third of their travel.

2. Yes, I've done auto-setup several times.

3. The MIDI encoder I'm using does not have any user adjustment facilities.

4. Operating the virtual expression pedals with the mouse does give a smooth response.

I think I have a compatibility issue with the expression pots as they are and the encoder, hence the request for info about an alternative encoder.
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GrahamH

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Re: Expression Pedal Range Issues

PostMon Jan 23, 2023 7:57 am

4. Operating the virtual expression pedals with the mouse does give a smooth response.


Do your virtual (on-screen) pedals move from fully closed to fully open in response to your physical pedals?
If so, that sounds very promising.

If you would like to send me a PM including your email address perhaps we could arrange for you to try one of my Arduino encoders.

Graham
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larason2

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Re: Expression Pedal Range Issues

PostMon Jan 23, 2023 8:47 am

In my opinion, rotary pots only work with a mechanism to amplify the movement. Can you replace them with a slide pot? If not, if it's linear there should be a way for the small amount of movement to correspond to the full range of pedal movement, but you may need a more sensitive encoder. Graham H may be able to help you there, but there are other solutions out there too, including mine!
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rayjcar

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Re: Expression Pedal Range Issues

PostMon Jan 23, 2023 9:57 am

Take a look at your Midi encoder output using Midi-Ox for Windows, or Midi Monitor if you're using a Mac. As you actuate the pedal, you should see a smooth transition between the minimum and maximum values detected by Hauptwerk. Also, given the limited arc of rotation of your potentiometers, ensure that you aren't up against the end stop. Hauptwerk doesn't care where the range of values begins and ends, it scales proportionately to the max and min values.

Ray
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jkinkennon

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Re: Expression Pedal Range Issues

PostMon Jan 23, 2023 1:59 pm

A properly programmed MIDI encoder should provide 127 discrete steps for the full travel of a potentiometer. That equates to about 40 discrete steps if only 30% of the pot's travel is possible. Look at a replacement encoder at least for the expression pedals. Otherwise, it's not difficult to add a linear pot. Numerous inexpensive linkages have been shared on this site and at the Organ Forum.
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Clavecin

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Re: Expression Pedal Range Issues

PostMon Jan 23, 2023 2:40 pm

PM sent to GrahamH
Looks like a way forward
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Clavecin

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Re: Expression Pedal Range Issues

PostWed Mar 01, 2023 12:53 pm

Post script:

Graham H very kindly supplied an Arduino device calibrated to the range of my pots.
Works perfectly.

Many thanks,
David

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