continus servo - not understanding how to move back to an exact position
Hello,
Using the parallax continuous rotation servo (which has been centered), BS2, Pbasic 2.5 on a BOE USB. I'm also not that familiar with servos :-)
My objective is to get the servo to sweep clockwise about 340 degrees or so through a circle, and I can do that with this code...
counter VAR Word
FOR counter = 1 TO 190
PULSOUT 15, 740
PAUSE 20
NEXT
END
So far so good. But I then want the servo to sweep back counterclockwise through the same arc, about 340 degrees. I thought this would do it, but it does not...
counter VAR Word
FOR counter = 1 TO 190
PULSOUT 15, 760
PAUSE 20
NEXT
END
Using the above, the servo sweeps back about only 270 degrees. Ny expectation (hope) was that it sweep the same distance, only in the other direction.
Given that the respective pulseout values are centered on the 'no motion' value of 750, what concept about servos am I missing?
Thanks,
John
Using the parallax continuous rotation servo (which has been centered), BS2, Pbasic 2.5 on a BOE USB. I'm also not that familiar with servos :-)
My objective is to get the servo to sweep clockwise about 340 degrees or so through a circle, and I can do that with this code...
counter VAR Word
FOR counter = 1 TO 190
PULSOUT 15, 740
PAUSE 20
NEXT
END
So far so good. But I then want the servo to sweep back counterclockwise through the same arc, about 340 degrees. I thought this would do it, but it does not...
counter VAR Word
FOR counter = 1 TO 190
PULSOUT 15, 760
PAUSE 20
NEXT
END
Using the above, the servo sweeps back about only 270 degrees. Ny expectation (hope) was that it sweep the same distance, only in the other direction.
Given that the respective pulseout values are centered on the 'no motion' value of 750, what concept about servos am I missing?
Thanks,
John
Comments
The only reliable solution to get a repeatable sweep is to use some form of feedback.
Rich H
<edit> Did a Google search and came up with these http://www.acroname.com/robotics/parts/R298-1T-SERVO.html there were many more options out there along with modifying a servo for more rotation.
John
A quick, related servo question. I've googled the topic and haven't found an answer. Does the standard servo provide some sort of feedback regarding its position?
Thanks,
Amanda
Yes, but that feedback is internal to the servo. In other words, the servo knows what it's position is but it doesn't share that information with you. You should know pretty well what it's position is because the servo does a good job of doing what it's told, as long as it is not under an excessive load.
Rich H