Please excuse my lack of knowledge, I have only just started reading about the arduino board and electronically controlling things in general.
I am currently in the process of designing a guitar for a course at school. I have come up with an idea for it, which is a string bending device.
3 strings would somehow be connected to a motor (stepper motor, I would guess) and would be able to be individually 'bent' (raised) a tone.
The stepper motors would be controlled by 3 foot levers (connected to potentiometers) and when pressed down fully would raise each string up a tone (it would turn the motor a certain degree). From what I have read an arduino board seems as though it would be a good starting point for figuring out how to go about my idea. As i am very new to this area of electronics, I am unsure if (when I eventually know enough) I would be able to create a purpose built circuit for this projects.
This is all just a concept, that i am unsure of how possible it is. Again, I am completely new to electronic controls, etc so this project could be impossible.
My questions:
Would you be able to calibrate the maximum turn of the motor to relate to the raising of a tone? Would this be done with the full resistance level of the pot? Or would you assign the maximum output in the software?
Would an arduino board be the best thing to control it with? or is it unneeded?
For anyone who has experience with relatively small stepper motors, would it be able to withstand the tension of a guitar string (around 20 pounds at most)?
I would appreciate any help greatly, as I am very excited about the possibility of this project. Please tell me if I have missed some vital explanation, etc that leads to my questions not making much sense
Three foot is a long leaver., could it be shorter.
Someone's going to slap you some day!
Yeah I think the problem will either be the amount of weight from a very powerful stepper/servo or the lack of speed if you gear a smaller one to get enough torque.
DC motors, have very good power to weight, and with high ratio gearboxes would likely be fine. In this case, you'd need to put an encoder on the motor so that you can get to specific positions.
If money is not a limitation, have a look at motors, gearboxes and encoders by Faulhaber. As well as being very good, their specifications are sufficiently detailed that you might be able to figure out out what would be suitable.
you could make some crazy batman-esque belt that housed the 3 motors and had 3 flexible drive shafts coming off that attached to the tuners of the guitar. it would look like an awesome devo nightmare.
Thanks for all the responses.
In regards to the weight, I would probably make the guitar body chambered, and use a lighter wood.
How does the torque relate to the amount of tension that can be held by the motor? In terms of pounds to the unit its measured in (mNm i think).
When it comes to programming the software, would it be pretty easy to do for what I require? Would I need 3 separate arduino boards for the motors, or can I control them all with just one? Im guessing that the Arduino would not power the motors, they would need to be separately powered (around 9v or so?).
Here is what gave me hope that I could use motors. This is a self tuning system that you can program to go to all kinds of crazy tunings. While it somewhat uses the same parts as what I want, the purpose is different. The sound of the string going up a tone is what I want to achieve, which of course would relate directly to how fast you push down on the foot lever.
I think they are likely to sell products which gets close to what you need, and their specs are clear enough to help (unlike lots of specs). Once you have something working well, you can look to ways to make it cheaper.
How fast do you want to 'bend' the note (and are you aiming for vibrato)? Combined with the tension in the string (which I imagine is published on the web) speed or frequency would determine a lot of the physics and hence mechanics of the solution.
My other question is does the guitar have to have the power supply for the motors inside it, or are you okay with an external power source?
i would try to score myself a set of the gibson robot tuners. there is a set on ebay at the moment, kinda pricey but they are nice and small and made for the job. then just run a ribbon cable up where the truss rod is to hook them up or something.
search for "gibson robot tuners" on ebay if you are interested
and here is a link to info on the robot guitar, incase you have never heard of it, it is a self tuning guitar that can go in to multiple tunings with the turn of a dial. for your application you would just use your own controller for the motorized tuners. (they still allow you to manually tune them as well)
"The tuning system used on the Gibson Robot Guitar is based on the aftermarket Powertune system, which was developed by the Tronical Company of Germany. The Gibson system uses the standard Tune-o-matic style bridge typical on their guitars, but modifications were made to have individual piezo saddles that transmit each string's pitch to the microprocessor. The computer analyzes the signal, and then controls each of the Powerhead Locking Tuners. Each tuner is run by a small servo motor that works in sync with the bridge to bring the string up to pitch by altering the string's tension until it is within a desired tolerance. The entire system is powered by a lithium-ion rechargeable battery housed in the control cavity of the guitar."
the new version of the tuners sounds much improved...
"The dimensions of the roboheads where reduced dramatically. The volume was more than halved.
The weight had been reduced to 33 grams. There is no need to clutch /declutch the roboheads before manual tuning any longer.
PT2 utilizes stepper motors instead of dc motors. This leads to a superior speed an accuracy. PT2 roboheads are capable of changing the frequency by 5 halftones per second."
so 5 half tones a second. you could meet your goal of one full tone in less than .5 seconds...that would keep things still sounding quite musical
