Controlling Servo Direction

Comments

• koolitude Posts: 37

  2007-01-30 08:11 edited 2007-01-30 08:11

  Please Help~~~~~~~~ Thanks~~~~~~~~~~
• Christj Posts: 13

  2007-01-30 08:16 edited 2007-01-30 08:16

  You can try these ...
  
  FOR i = 1 TO 20
  PULSOUT 12, 650
  PULSOUT 13, 850
  PAUSE 20
  NEXT
  
  Don't forget to adjust the servo, so it will be stop when giving a 750 width pulse.
• koolitude Posts: 37

  2007-01-30 08:18 edited 2007-01-30 08:18

  Thanks a lot...
  
  just some follow up questions....
  
  Would the speeds of the motors be the same?
  
  How did you decide the value of 650 and 850?
  
  Thanks once again~~~~~~~~~~~~~~~~~~
• Bill Chennault Posts: 1,198

  2007-01-30 13:53 edited 2007-01-30 13:53

  koolitude--
  
  Just download the book "What's a Microcontroller?" Parallax makes it available for free download. You can either download it or read it online at . . .
  
  http://www.parallax.com/dl/docs/books/edu/Wamv2_2.pdf
  
  In any case, I believe exactly what you want is in chapter 4, which begins on page 103.
  
  Have fun!
  
  --Bill
  
  
  ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
  You are what you write.
• LSB Posts: 175

  2007-01-30 14:13 edited 2007-01-30 14:13

  Servos are commanded to position by signals between 1000 and 2000 ms; 1500 is center. The pulsout command outputs in 2ms steps so... pulsout 500 moves an UNMODIFIED servo to full anticlockwise, pulsout 1000 move the unmdified servo to full clockwise position and pulsout 750 is center. The servo 'knows' these positions, because it turns a potentiometer as the motor turns and, when the two signals agree, the servo is in position. This is useful in a variety of ways (but doesn't answer your question). If the servo is 'modified' in that the feedback potentiometer is disconncted, the servo will continue to spin 'continuously' as it tries to find the motor position where the pot signal and the motor position agree. Pulseouts > 750 turn the motor clockwise to search, pulseouts < 750 turn the motor anticlockwise to search. "Centering" the servo is the act or process of adjusting the disconnected pot so that at a pulsout of 750, the pot and the motor position agree... therefore the motor remains still.
  In practice, one sends pulsout 750 to the modified servo and adjusts the pot until the motor stops turning, then sends pulsouts of > 750 to move the 'bot forward and <750 to move it opposite. Since the servos are likely mounted on opposite sides of the robot, one servo must go clockwise and one must go anticlockwise to move both wheels 'forward', hence Christj's code commands one servo to 650 (<750) and one to 850 (>750).
• PAR Posts: 285

  2007-01-30 21:22 edited 2007-01-30 21:22

  Servos are commanded to position by signals between 1000 and 2000 ms; 1500 is center. ...

  Actually, between 1 and 2 milliseconds (ms), or 1000 and 2000 microseconds (us).
  
  PAR
• LSB Posts: 175

  2007-01-30 23:53 edited 2007-01-30 23:53

  Right, right. Thank you for the correction.
• koolitude Posts: 37

  2007-01-31 08:53 edited 2007-01-31 08:53

  Thank you very much for all your help!
  Y'all are very helpful!