Servo Speed

Support Servo controllers and servos
1

Hi Guys
Im struggling to set the servo speed in my program.

Servo’s run as per button presses, but runs at full speed,how do I set each servo’s speed in my script?

below is my current working script without speed adjustments:

goto main_loop    # Run the main loop when the script starts (see below).
 
# This subroutine returns 1 if the button is pressed, 0 otherwise.
# To convert the input value (0-1023) to a digital value (0 or 1) representing
# the state of the button, we make a comparison to an arbitrary threshold (500).
# This subroutine puts a logical value of 1 or a 0 on the stack, depending
# on whether the button is pressed or not.
sub button
  0 get_position 500 less_than
  return
 
# This subroutine uses the BUTTON subroutine above to wait for a button press,
# including a small delay to eliminate noise or bounces on the input.
sub wait_for_button_press
  wait_for_button_open_10ms
  wait_for_button_closed_10ms
  return
 
# Wait for the button to be NOT pressed for at least 10 ms.
sub wait_for_button_open_10ms
  get_ms # put the current time on the stack
  begin
    # reset the time on the stack if it is pressed
    button
    if
      drop get_ms
    else
      get_ms over minus 10 greater_than
      if drop return endif
    endif
  repeat
 
# Wait for the button to be pressed for at least 10 ms.
sub wait_for_button_closed_10ms
  get_ms
  begin
    # reset the time on the stack if it is not pressed
    button
    if
      get_ms over minus 10 greater_than
      if drop return endif
    else
      drop get_ms
    endif
  repeat
 
# An example of how to use wait_for_button_press is shown below:
 
# Uses WAIT_FOR_BUTTON_PRESS to allow a user to step through
# a sequence of positions on servo 1.
main_loop:
begin
  7300 frame_3 
  1000 frame_2
  1000 frame
  1000 frame_3
  7400 frame_3
  10000 frame
  10000 frame_2
  7200 frame_3
repeat
 
sub frame
  wait_for_button_press
  1 servo
  return  

sub frame_2
  wait_for_button_press
  2 servo
  return

sub frame_3
  wait_for_button_press
  5 servo
3

As far as I know Servo motors get as input a PWM signal where a pulse width of 1ms moves it to one extreme, 1.5 ms to the center and 2ms to the other extreme (correct me if I’m wrong on the timings). A software solution may be to iteratively change the position of the motor according to some time difference between main loop iterations. I don’t know what hardware you use but it is very probable you have all the components to do so by hardware and if so, it is more preferable to do it by hardware.

Therefore, I think we will be able to give you a better answer if you will give us more information on your setup:

  • What hardware do you use?
  • What software do you use?
4

Im using the pololu 6 channel servo controler with 3 servo’s and one push button.
Using the software that came with the pololu controler

5

I looked a bit in the manual for this controller in https://www.pololu.com/docs/0J40/6.c

Look at the section “Making smooth sequences with GET_MOVING_STATE” - they have the following line in the code:

30 0 speed

I read their manual a bit and found out that the first argument is the speed in 0.25 (servo) microseconds per 10 milliseconds and the second argument is the servo channel.

Take a look at their User’s guide at https://www.pololu.com/docs/0J40 mostly at chapter 6.

6

Hello.

To set servo speed from a script, you can use the speed command. More information on how that command works can be found under the Command Reference section of the Maestro’s user’s guide. You can also find an example showing the use of that command under the “Making smooth sequences with GET_MOVING_STATE” example script, which can be found under the “Example Scripts” section of the user’s guide. (You can finder the user’s guide under the Resources tab of the Maestro’s product page.)

By the way, you can configure the default speed limit applied to each channel at startup in the “Channel Settings” tab of the Maestro Control Center. This is especially appealing if you do not need your servos to change speeds throughout your script. (Be sure to click Apply Settings in the bottom right corner of the Maestro Control Center to save your settings.)

-Jon