Using 2 Continuous Rotation Servos at Once

Comments

• Mike Green Posts: 23,101

  2015-10-24 14:24 edited 2015-10-24 14:40

  ' count1 is time to run for servo 1 (20ms units)
  ' time1 is servo 1 control pulse width (2us units)
  ' count2 & time2 are similar for servo 2
  
  ' This loop outputs servo control pulses as needed for
  ' servos 1 and 2 approximately every 20ms compensating
  ' for the times needed for the control pulses.  When both
  ' servos are no longer running, the loop stops.
  
  do while count1 > 0 and count2 > 0
    delay = 10000  ' 20 milliseconds
    if count1 > 0 then  ' servo 1 still running
      pulsout servo1,time1  ' PULSOUT takes time1 to execute
      delay = delay - time1  ' adjust for that (2us per unit)
      count1 = count1 - 1  ' one less 20ms period to go
    endif
    if count2 > 0 then  ' same thing for servo 2
      pulsout servo2,time2
      delay = delay - time2
      count2 = count2 - 1
    endif
    pause delay / 500  ' delay 20ms less time for servo pulses
  loop
  

  
  The above code will run both servos at the same time with independent speed settings and durations, but servos are pretty sloppy. How are you going to ensure that you've moved to the coordinates you think you've moved to, particularly after several moves?
  
• erco Posts: 20,261

  2015-10-24 17:19

  Per Mike, you can certainly move 2 CR servos simultaneously, but they don't have any positional feedback. Speed ( thus transit time) varies with load, voltage, and other variables , so you'll never move very accurately. Errors get larger, unless you add encoders.