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Re: gEDA-user: OT - Joystick control of stepper or servo motors

     Hi, electronics gurus!  I'm looking for suggestions on the best
     inexpensive way to use a USB game joystick to control stepper or
     servo motors.
     The application is using a joystick to drive the the platform
     positioning knobs on a microscope, to help me keep the subjects in
     the field of view, while I'm photographing them.  I'll also be
     adding the ability to trigger the camera shutter with the joy stick,
     but I don't anticipate any trouble with that part; it's the motion
     control side that I have no experience with.
     Any suggestions?  Are steppers or servos better for this use?  What
     should I use to control them, Arduino or a generic motor control
     For background, I'm working as a programmer now, so I can handle the
     programming.  My degree is in EE, but I haven't used it in ~20
     years, so I'm kind of rusty on the electronics side but I'm sure it
     will come back.

     I have been trying (not hard enough, obviously)  for a year or two to
   read the position and buttons of a USB joystick with a C program
   running on a laptop to convert them into drive signals for my under
   water ROV. If you or anyone else knows of code that I can use for
   reading the joystick, I would certainly appreciate hearing about it, as
   the under water robotics competition is coming up again this June.
      For your application, I strongly recommend dropping the USB joystick
   and using a [1]two potentiometer analog joystick feeding directly into
   an Arduino or Atmel chip. It can easily read the left-right and up-down
   signals, and use them to control either DC motors or stepper motors. DC
   motors are easier to control, and I assume you will have a gear train
   to slow the motor shaft speed down to the normal knob turning speed
   that the microscope expects. You can use a [2]dual DC H-Bridge motor
   controller or a pair of[3] stepper motor drivers to convert signals
   from the Arduino/Atmel into motor drives. With the DC motors you want
   PWM signals to control motor speed based on joystick angle, and with
   stepper motors you want to vary the pulse rate to control the speed of
   the steppers.


   1. http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=252A104B60NB-ND
   2. http://www.robotshop.com/solarbotics-l298-motor-driver-kit.html?utm_source=google&utm_medium=base&utm_campaign=jos
   3. http://www.pololu.com/catalog/product/1201

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