I'm working right now on a small system that will allow you to control a standard potentiometer using either MIDI or Expresion pedals. There is a lot of things to work on but i will present you the concept.
The idea behind this was simple: a electro-mechanical module that can be used virtually on any guitar amplifier to control various functions (potentiometers) and also preset storing (MIDI CC messages will be used). Also another requirement was this: anyone with a screwdriver should be able to fit it into position and give it a go in under 10 minutes.
The project is using a very small stepper motor with 1.8deg / step (standard) and it will be controlled in full step mode using a dedicated driver. The shaft of the motor will be directly connected to the shaft of the potentiometer using an elastic coupling (similar with the ones that are used in CNCs). That will allow me to have quite an ok resolution for both models of potentiometers 270deg. and 300deg. (a small switch will select the model of potentiometer).
The "zero point" setting will be made using an optical slot sensor (infrared) that will set the zero point of the motor (each motor will have a home button that will allow you to set the zero point before you will connect the potentiometer to the elastic coupling).
The system will have only 23mm wide (the motor is only 20mm wide) and can accommodate quite a large number of amplifiers. The command box will allow you to use MIDI or an expression pedal. The command unit will be able to drive a maximum number of 5 modules.
Now... because of some certain reasons i've decided that each motor will have its own drive module that will be made by a stepper motor drive unit and a microcontroller unit - MIDI signal will be split in 5 (using some inverting buffers) and each motor will be independently commanded.
The reasons are:
- modularity (maybe some users will need 2 modules instead of 5 so.... he will buy only 2)
- programs are executed in a seq. mode inside a uController so if you like to actuate the motors in the same time... well you would need parallel processing and this is what i'm doing but in a more accessible way
- fault isolation (in a live situation is mandatory)
Now some ... things i would like to clarify :
- this system is designed for existing amps / preamps / power-amps etc for a new design motorized potentiometers can be used
- NO is not the same with the system presented at NAMM this year - totally different approach / driving methods / driving elements etc. And yes my system is faster in terms of rotating speed from point A to point B
- Yes i know the system designed for Neil Young and no
it's not the same The above notes were just a collection of questions that i've received in various situations.
In the end the project will be posted on kick-starter (along with another quite popular project - THE GTFO) and will be posted in Open Source community free for personal use (i'm trying right now to get a small patent for it at least in EU - software and design).
Now long story short some pictures with from the building phase - as i said a long way to go especially now because i'm going to change my shop location in couple of days but i would like to finish an working prototype until the end of the month.
Relevant comments are highly appreciated and encouraged. Also as an ending note, there are other ways for zero-point detection but some are more expensive, some are not suitable for such a small stepper.
Regards,
DeX
