Stepper Motor Pedal Steel

[Benjamin Poilve]

Nice prototype!

Out of curiosity, what is the maximum speed for a half-tone bend?

If you are looking for solutions for the pedal bar sensing, I designed a PCB with hall sensor and an I2C ADC, it works quite well to detect the orientation of a magnet (see video here for a demo of the orientation mapped on pitch:https://www.benjaminpoilve.com/sources/ ... 5088~2.mp4).




This is a 4-pedal sensor, would be happy to share the schematics if that can help !

[Eric Moon]

might be useful, I'll keep it in mind, thanks!

I'm aiming for 20ms for a semitone, but I think I'll need the more powerful motor to do that.

It will also depend on how much string tension there is. A tighter string slows down the motor... A lot of unknowns still. Right now, I'm trying to decode the info from the encoder... have to get the software working to test further.

[Eric Moon]

oh hi Benjamin. Just saw your project elsewhere on the forum, and sent you an email.

Did some tests today on what this motor can handle. At 20 lbs of string tension, it can do a semitone in 30 ms. At 23 lbs of tension it takes 100 ms. So big difference there. Adjusting the compensating spring could shift that, but I need to buy a sturdier spring, as this one is stretched far past its useful range.

This is based on values from the stringjoy string tension calculator.

[Benjamin Poilve]

I answered you last week !

Very impressive, 30ms is definitely usable, I did not expect those motors to be that fast !
Do you have a PID to regulate the movement with the encoder feedback or is that open loop?

[Eric Moon]

Yeah, closed loop for sure. I'm trying to tune the PID right now. The problem is not speed, it's accuracy. If you don't land close enough to pitch on your first try, then it's a slow process adjusting--the motor needs most of its power to move the pitch, and once it does, it goes too far too fast! So there may need to be some pretty sophisticated ballistics involved. I need to get a better test-bed for PID, so I can adjust in real time. I summarized my thoughts here:
https://groups.google.com/u/2/g/diy-pid-control

I did not get an email from you that I can find, and I don't have any private messages here... hmmm. Try again, maybe?

[John Sims]

Lots of good ideas. Maybe we should have a contest to see who can build the best 1-string electro-mechanical pedal steel changer prototype.

How 'bout a 5 or 6 string that can do everything an 8 X 5 10 or 12 string would do? It's all in the software I guess...

[Don Christy]

What if the steel had 10 of these DC solenoids connected to a bracket and mounted under the steel next to the changer and had short pull rods for each changer finger. You could have more solenoids for each upper or lower changer finger too.

All the pedals and knee levers would be electronically operated to make the solenoid pull the short changer rod for that changer finger when played.

You would eliminate weight by not having cross shafts...bell cranks...long pull rods

Its and idea I had when reading these post on here. There are all kinds of DC solenoids that are made small these days.

[Don Christy]

Georg Sørtun...if there were a solenoid that had variable travel speeds...is it possible this could work?

Got this idea about how variable speed drills are built. Even some homes have light switches that are variable when turning the knob on the switch.

Maybe the pedals and knee levers could have these little variable rheostats to make a certain solenoid operate slow or fast when needed.

Georg, do you have any thoughts on a certain solenoid that might work the best to make a prototype?

When I retired I was going to buy an old 10 string pedal steel and see if I could make a prototype with solenoids. There are so many new gidgets these days that its overwhelming.

[Benjamin Poilve]

Some semi-proportional solenoid do exist, that could be precise enough for slow pulls.
Basically it makes up for the unwanted non-linearity of a solenoid (ie it pulls more at the end of the travel, because more plunger is between the coils), by a smart geometry and compensation springs.
Not ideal, but might be linear enough, especially since you (with your ear) arr "closing the loop" when you play (ie even if this is not strictly linear, you will make up for it naturally with your feet.

[Bill Ferguson]

Quite a few years back, Carl Dixon, designed and actually incorporated a micro system to control the changes on a pedal steel.
He had Mitsuo Build him a steel to his own specs and had everything installed and working, but found a flaw in the way he ordered the steel, thus stopping him in his tracks.

To my knowledge, this "many thousand $$) machine is still sitting on his workbench untouched.

He said he guessed that he would just toss it in a dumpster or let his kids do the same after he passed.

It is a shame. Carl spent many years designing, testing and proving that it could be done.

The top of the Excel looked like a cockpit, with all the various controls.

[J D Sauser]

IF one goes that far into electronics, would it not make more sense to just pitch-shift the each string's output (individual pickups) and program the setup (pitch shifts per pedal & lever and string) via a Bluetooth App on one's cell phone?

IIRC, ed packard went down that route, and presented his ideas and test results here on the forum.

Me; why not combine all ideas in one instruments?

I removed some of the back and forth resulting from my "hijack".

Yes, evidently no sense in combining Stepper Motor/Solenoid with Digital Pitch Shifting as the later cancels all need for mechanics.
But Stepper Motor/Solenoid with Left Change and Floating Bodies... and so forth. Of course! IF one revolutionizes, it would seem natural to look at everything.

I was a model aircraft hobbyist as a teen, just when "Proportional-RC" became the new thing. 50gr Servo-Motors controlled by a receiver the size of two matchboxes with AM and soon there after FM RC controls.. all proportional. We're talking 80's!

I would assume that almost 40 years later the Stepper Motor or Solenoid option is definitely doable.
Still, while our instrument is "electric", the idea of having to plug in my guitar into a wall outlet (since the motors have to overcome considerable mechanical resistance and with agility, so it can been played at all, is... worrying me somewhat. But only somewhat.

All strings being attached to one or two (raise and lower) stepper motors, may allow for programmed compensation of ALL strings and even Change-Compensation when played in combinations of pedals and levers!
So, given the combination, not only "unaffected" string could be micro compensated, but the actual change pulls micro-managed too.
Let's assume in E9th, you tune E-to-F to the A-pedal as a C# Major triad.
But then the F-note is JI tuned flat to the already flat C# root which was tuned as a M3rd to the A&B-pedaled A-chord. When you use the E-to-F change with A&B down, wouldn't it be nice that WITH that combination it would be less flat for a good sounding Augmented?
Once we go "electronic" se evidently can go "smart" at once. Set the setup via a Bluetooth App on a SmartPhone to a variety of pre-programmed setups!



.... J-D.

[b0b]

All strings being attached to one or two (raise and lower) stepper motors, may allow for programmed compensation of ALL strings and even Change-Compensation when played in combinations of pedals and levers!
So, given the combination, not only "unaffected" string could be micro compensated, but the actual change pulls micro-managed too.
Let's assume in E9th, you tune E-to-F to the A-pedal as a C# Major triad.
But then the F-note is JI tuned flat to the already flat C# root which was tuned as a M3rd to the A&B-pedaled A-chord. When you use the E-to-F change with A&B down, wouldn't it be nice that WITH that combination it would be less flat for a good sounding Augmented?
Once we go "electronic" se evidently can go "smart" at once. Set the setup via a Bluetooth App on a SmartPhone to a variety of pre-programmed setups!

.... J-D.

I worry about obsolescence in such a design. Many of us love to play pedal steels that were made made 50 years ago. Will Bluetooth and smartphone apps be available 50 years from now, or even 10? That's why the programmable controller design I envisioned 20 years ago in Pedal-Steel-Changer-Controller.pdf was completely contained within the guitar.

[J D Sauser]

I can relate to your view very well. I have houseS stuck full with vintage instruments, still insist to play thru JBL D130 and old amps and all my acoustic Jazz guitars are vintage (30's thru 70's), and you can well imagine my Hawaiians! I just acquired a number of Emmons PP's... all BoltOn and a WrapAround (and no, NOT because I prototype around getting THAT sound! But I wanted to try them and compare.)

Yet, I am not exactly a kid anymore. Neither are many steel guitar players and fellow Forumites.

My main goal with PSG is two-fold:
TONE & The expected versatility.

I think you can relate to that too. After all, you got a New Sierra which promises just that.
Evidently, one can take several approaches to that. MSA does it in a very "traditional" way, in contrast.

Evidently, a fully "electronic", "smart" guitar WILL be snubbed by many as "not real", EVEN if the tone would be superior (no changer messing up the tone). Just like there was and still is a resistance against electrically amplified Guitars, Violins and still electronic "Pianos".
But I think that there is a crowd already here and one that will come with generations to come which will view it for it's versatility, consistent tone and ease.

You know that I am a pretty "mechanical" person. I was trained a precision tool and machinery engineer in Switzerland. The leverage system used since PSG's is, lets admit, primitive. As I posted watchmakers made much more advanced contraptions in the late 1700's! The evolution in PSG we have witnessed from the 40's thru now (really stagnated in the 80's) is NOT in par with other industries' technical evolution simply because Steel Guitars have almost always been a niche market associated to no-so-intellectually respected popular music and it's development mostly in the hands of "garage"-hobbyists and "hillbilly-tinkerers" (nothing wrong with "Hillbilly"... but not exactly the mind set that got the Russian to build the Sputnik or the US to the Moon... but THERE's a comparison(!)... imagine the PSG's available on the day Armstrong set foot on the Moon!).

Since the 80's we haven't seen much development... just more of the same in some sort or shape: Sierra was building a full very "mechanical" guitar, Zum had established itself as the "Emmons"-looking mechanically sound built solid guitar (perfecting a 20 year old concept of looks (compact, non-woody)). MSA assembling a mass produced instrument with mass produced parts.

30 years plus later... what's new?
- CNC has become affordable.
- Digital design allows for quick remote fabrication of parts.
- Extrusion has become affordable (Carter was one of the first to take full advantage of that).
- And finally ONE builder is working on floating sound boards.
- And few builders have changers which have more changes available as previously imaginable.

- AMPS and speakers have changed. My 11-year old can carry my current "stage amp" (BlackStar 100) which has "Stereo"-surround sound all built in.
- My practice amp (Vox Adio) looks more like a woman's handbag sounds better than any of my beloved vintage amps and certainly better than any of the amps EVERYBODY felt had to terrorize their bedroom with, with it's 200Watts ... and BOTH can be adjusted with one's "Smart"-Phone". I frowned at first... but now I got my tuner on my phone... since I sadly carry it everywhere I go, I don't have to look for the tuner etc anymore. I surrendered, yes I did... and sometimes am ashamed to admit.


I currently play a S12 with 6 pedals and 8 levers I can operate without repositioning myself. GIVEN, not everybody's dream or nightmare.
I love having been able to make that work. Currently I have it setup that way on two Excel's. Jim Palenscar is trying hard to make it happen on my "new" MSA S12, and I am confident he will.
I have commissioned Sierra to build one too like that and got the "nod" (with some eye rolls!).

Still, what I want, is ALL the above, with a quality non-pedal tonal quality and dynamics.

- Electronically generated/controlled mechanical pulls (Stepper Motors/Solenoids) MAY depending on the changer they control.
- Left-End Changer can bring that about.
- NO-Changer (Digital Pitch Shifting) promises at least the same result. And could be made to look any way from "vintage-woody" to "Darth Vader" horrid.

Thanks!... J-D.

All strings being attached to one or two (raise and lower) stepper motors, may allow for programmed compensation of ALL strings and even Change-Compensation when played in combinations of pedals and levers!
So, given the combination, not only "unaffected" string could be micro compensated, but the actual change pulls micro-managed too.
Let's assume in E9th, you tune E-to-F to the A-pedal as a C# Major triad.
But then the F-note is JI tuned flat to the already flat C# root which was tuned as a M3rd to the A&B-pedaled A-chord. When you use the E-to-F change with A&B down, wouldn't it be nice that WITH that combination it would be less flat for a good sounding Augmented?
Once we go "electronic" se evidently can go "smart" at once. Set the setup via a Bluetooth App on a SmartPhone to a variety of pre-programmed setups!

.... J-D.

I worry about obsolescence in such a design. Many of us love to play pedal steels that were made made 50 years ago. Will Bluetooth and smartphone apps be available 50 years from now, or even 10? That's why the programmable controller design I envisioned 20 years ago in Pedal-Steel-Changer-Controller.pdf was completely contained within the guitar.

[Eric Moon]

Well, if you pop over to the maker thread, you will see someone has gone ahead and done this. So I am un-backburnering my own project, since it has definitively been proven to be possible!

https://forum.makerforums.info/t/buildi ... /84597/118

He has more posts in the Steel Guitar Builder's forum on facebook.

He uses servos, such as used in remote control model cars, which are available with plenty of power and speed, at the expense of compactness. But I can work around that...

He actually uses wireless for the pedals, and joystick controllers for the knee levers. All very clever and quite well implemented, including a single switch that converts the tuning from E9 to C6!

[Jacobus De Bruyn]

Hi. I build the Electro Steel in the forum. I am designing my second Electro Steel and will use stepper motors instead of servo motors this time. Although the servo motors do a great job, I can hear them when operating. Did you ended up using stepper motors, if so how loud are they when actually pulling a string. No load seems quiet.