Homebrew gadget to display EV-1 volume pedal position

[Fotukito]

If you enjoy reading about delightfully over-engineered solutions, read on…

tldr; I’ve built an Arduino-based gadget to display LED patterns on my pedal board to visually inform me of the position of my EV-1, which I use as an Axe volume pedal.

The ‘Problem’...

As a part of a small live act (duo) playing with backing tracks, lots of MIDI-based automation, and mostly for events too casual to have anyone working FOH, our repertoire is necessarily ‘pre-mixed’ with repeatable gain staging from instrument to PA. Though the pre-programmed MIDI automation also takes care of my guitar volume changes within each song, I still have an EV-1 in expression mode to control my Axe FX III volume in case I want to make minor tweaks (+/- 3dB) or perform swells.

It’s important for the volume pedal to stay in the ‘nominal’ position, which is about 60% depressed, for most of a gig, since everything was gain-staged that way when we ‘pre-mixed’.

However, there’s no easy way to check if the pedal is that nominal position, other than to check a tiny text value I’ve got displayed on the Axe performance page, which is inconvenient during a gig.

How can I easily verify my volume pedal is in the right position to match our carefully pre-mixed gain staging??

The Solution…

Using an Arduino Uno processor, Adafruit LED matrix, and some software, I built a gadget mounted to my simple pedal board that ‘reads’ the position of the EV-1 (measuring the same voltage the Axe uses for its expression pedal processing) and then displays a LED pattern that reflects the corresponding Axe volume boost/cut.

See this 30 second video for an example of it working (LEDs don't capture well in an iPhone, but you can get the idea)...




Really, it’s just the pair of LEDs that tell me ‘pedal is nominal position’ that I really need; the rest of the LED patterns are just fun eye candy. But it was a fun project and interesting proof of concept, since the idea could be used with any expression pedal. (E.g., imagine a blinking red LED if you’ve left the wah cocked ;-)

 

[Musikron]

That's pretty slick. What was the build cost and difficulty level? I can think of about a half dozen different uses for that.

 

[touch33]

I can’t decide if you get a “clever, clever” or a coveted “fuckin’ brilliant” rating. Either way — WELL DONE! I foresee an entirely new definition for “shoe gazer”…

 

[touch33]

I’d like mine to have a “press and hold to learn” foot switch, please!

 

[bdrepko]

There was one or two times when I was gigging that I couldnt hear myself. When I looked down at my board I noticed that the volume pedal was heel down. I put a couple of springs in the back part of the pedal to keep the pedal in the toe down position. It does work pretty well. Bit this seems like a better solution.

 

[mr_fender]

Cool project. The amount of really cool stuff you can do with tiny dirt cheap processors like Arduinos and Raspberry Pi's these days is really awesome. I mean the Arduino Nano is like the size of a couple of postage stamps. I wish I had stuff like this to mess with when I was a kid.

 

[Fotukito]

That's pretty slick. What was the build cost and difficulty level? I can think of about a half dozen different uses for that.

Since this was my first Arduino project, I went with mainstream components:

Arduino Uno: $21
Adafruit NeoPixel Shield (LED matrix): $28
ProtoStax Enclosure: $15

I have programming and C experience, so that aspect was not difficult. The Arduino open source community has an impressive amount of code available to review and reuse to get a good jump start.

For the build, just basic soldering skills were good enough.

I did modify my EV-1 internals: Since I’m only using it as an expression pedal (to drive Axe volume-related parameters), I sacrificed the EV-1 Volume In jack so it could conveniently pass the expression potentiometer wiper signal to the Arduino via a standard TS cable. For that I had to do some signal tracing and ended up adding a short jumper and cutting one wire on a ribbon cable within the EV-1.

If I built it again (for my particular application), I’d probably go for a smaller board (maybe Arduino Nano?), a smaller LED array, and make my own case, which would save $ but more importantly reduce the footprint significantly.

OTOH, I think about adding MIDI support… pretty cool if it could dynamically change the kinds of info it displays depending on the role an expression cable is taking. ;-)

 

[Fotukito]

I’d like mine to have a “press and hold to learn” foot switch, please!

Yea, that would be nice! For this app (which uses 15 distinct LED patterns across the range of pedal motion), I had to match debug readings from the Arduino (to a PC connected temporarily by USB) with Axe dB readings, to create the table that correlates pedal position (and thus LED pattern) with the Axe readings.

 

[Fotukito]

There was one or two times when I was gigging that I couldnt hear myself. When I looked down at my board I noticed that the volume pedal was heel down. I put a couple of springs in the back part of the pedal to keep the pedal in the toe down position. It does work pretty well. Bit this seems like a better solution.

LOL!
For me the predecessor to this blinky solution was analogous to marked tape on a knob: I mounted a piece of wood next to the pedal cut to just the right length so that if I twisted my foot slightly to the right and could feel that the pedal and the top of the stick were along the same plane, it meant I was at nominal volume. But I still needed to use my feet and I'm lazy and bllinky LEDs are much more fun.