Midi Fader/Pot Control for Effects Pedal

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critterkllr

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Joined
Nov 5, 2010
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311
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Dearborn, MI
I wanted to run this past everybody to see if any of you have some advice or input on this. My plan is to use arduino to interface midi to control a few motorized potentiometers and switches for an effects pedal.

The effects pedal will have 6 motorized pots and one rotary switch. The pots and switch will respond to individually assigned midi CCs. There won't be a need for internal memory for presets since I have an external midi interface that saves midi batches and sends them out according to an incoming midi PC #. So, I will be able to control the knobs externally using a midi controller and I can save a preset by simply sending the CC# corresponding to the knob position that I want.

I like the idea of motorized pots because I want to be able to use the pedal by itself without using a separate midi controller. It's also nice to see knob positions and hell... it'll look pretty cool!

I'm pretty new to the world of digital control and was wondering if any other routes are advisable before I dive in on this. Saving money isn't a concern over functionality. Is there a different route that is more reliable/consistent? Are there are certain aspects of components that work better than others (for example, faders are nicer to work with than rotary pots)? I understand that I'll want to isolate the digital power and ground from the analog pedal, but don't know how that works if the potentiometer itself is grounded to the chassis. It's a fuzz pedal so it's gonna be noisy and picky about interference.
 
You might want to look here http://ucapps.de/
They have motor driver code and pcb's there that might save you quite a bit of work.  That's if you want to save yourself quite a bit of work ......

In particular the Motor fader NG module !!
 
Another way to do it would be to use encoders with a ring of LEDs instead of motorized pots.  The LEDs indicate where the setting is, doesn't matter where the encoder is set. I have seen this on a guitar pod knockoff for example.
 
Rob Flinn said:
You might want to look here http://ucapps.de/
They have motor driver code and pcb's there that might save you quite a bit of work.  That's if you want to save yourself quite a bit of work ......

In particular the Motor fader NG module !!

Very cool! I searched that site high and low, but somehow missed the MF_NG Module.  It looks perfect for my project, except I don't know if there is a difference in design between high quality faders and the smaller motorized pots. I will look into it and see if it will work out.

Another way to do it would be to use encoders with a ring of LEDs instead of motorized pots.  The LEDs indicate where the setting is, doesn't matter where the encoder is set. I have seen this on a guitar pod knockoff for example.

I've seen this used on a lot of things, like Moog synths. I've also seen it used where one simple LED is shown as yellow until the previous stored state is hit, then turns green. My worry with this is that around half of the time I've used digital pots like this, the values jump around quite a bit and seem unstable. Maybe they were older designs? I'm not sure.

My biggest weakness is metal work, so if I went through digital route, it would have to be simple for me to fabricate. The idea of a ring of LEDs around the pot makes me start to get queasy.

I want to insure that if something happens on the digital control side, the pedal will still function completely fine. This will be taken on the road a lot and I worry about add-ons creating more opportunities to fail.
 

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