Strain Gauge Effect

[Rob Strand]

Phono cartridge ? Very small motion, but mounted in the right place on a cantilever of calculated (or measured) deflection might have a usable output ?

The output voltage is proportional to velocity, so no output with constant deflection.  A speaker cone is similar.  You will get a pulse when you push and release.   You might be able to detect scratching if the needle touches a surface.

Most sensors need for something to change position.   For the strain-gauges there is movement but it is small enough to be considered stationary.

Mark mentioned hall-effect devices.   There's linear output versions and also on/off "processed" versions.    One of the Ibanez wah pedals uses a Hall device.

There's, capacitive and inductive sensors, also LVDT (more like a transformer).   Often these require  a synchronous detector to fend-off noise.

Light has been used in the past because you can create a light source which is stronger than the background noise.   Many of those use still end-up using synchonous techniques.    There's some cool tricks using interferometry and light to detect small movements checkout some videos on youtube - for DIY parts it's pretty rough and not really controlled enough to use on a product.

I forgot to mention above, for air controlled devices you can use a flow sensor.  Normally you would blow through a tube which is open and measure flow as opposed to blowing into a blocked tube and measuring pressure.

The reoccurring problem with alternate technologies is you need to throw more electronics at it.   If you think about the touch screen on your phone, it's a widely used an accepted but there is actually a whole lot of electronics machinery under the hood.   That in itself more complex than most pedals.  I guess the point I'm making is in order to go forward you need the raise the bar in terms of how much electronics you are willing to throw at it.

[Phend]

Interesting how your phone or tablet detects vertical from horizontal.  A cantilever. Check it out. And start etching !

[Rob Strand]

Interesting how your phone or tablet detects vertical from horizontal.  A cantilever. Check it out. And start etching !

Very cool.

Ultimately it's measuring capacitance, or perhaps relative capacitance.

https://www.sciencedirect.com/topics/engineering/capacitive-accelerometer

There was fairly simple circuit to do this in ED Magazine back in the 90's.  Believe it or not I have a photocopy of that article on my desk!  "Bridge Measures Small Capacitance" by Jeff Witt from LT, Ideas for Design, ED Magazine, Nov 1996.

Instead of trying to do your own perhaps it's not a bad idea to buy off the shelf stuff from the consumer market.

Here you go, virtually the same article.  Last article around p41.
https://www.analog.com/media/en/technical-documentation/lt-journal-article/LTMag_V06N3_Aug96.pdf

[Mark Hammer]

Accelerometers are finding their way into plenty of musical products.  Several "pot-less" EHX foot pedals use accelerometer technology to detect foot motion.  The Source Audio Hot Hand controller also uses an accelerometer to determine hand position.

I bought a BBC Micro:bit a few years ago, and it also has an accelerometer onboard.  I'll have to think about something musical I could do with it that makes use of the tilt.

[PRR]

Phono cartridge ?

Panasonic tried it, sold it. Didn't take-over the market. Amusing because it can be low-Z and, with large excitation, a not-small output.
https://www.diyaudio.com/forums/analogue-source/307849-playing-panasonic-strain-gauge-cartridges-dedicated-phono-stage.html

[EBK]

Accelerometers are finding their way into plenty of musical products.  Several "pot-less" EHX foot pedals use accelerometer technology to detect foot motion.  The Source Audio Hot Hand controller also uses an accelerometer to determine hand position.

I wouldn't recommend this approach.  The best you can hope for from using just an accelerometer is a rough estimate of relative position.  You would need something to reliably reset the absolute position and correct for drift. It would likely be glitchy as hell.

There are some sophisticated position sensors that use accelerometers, gyroscopes, and compasses, but I doubt any pedal company is using them.  If you want to go that route, I'd suggest writing an app that uses a smartphone's position sensor and stick the phone inside the pedal.