Answers.Body: <p>If you don't need constant speed motion a better idea would be to use a crank running from any modern motor (ie, geared down internally). That way you can guarantee the end points. For a 240° rotation you might need to gear up after the crank, but as long as there's a spring or constant load in one direction backlash shouldn't be an issue.</p>
  
  <p><img src="https://i.sstatic.net/eTRKv.png" alt="enter image description here"></p>
  
  <p>Here;s a really quick sketch of what I mean. Your motor drives the black axle in the foreground, and that rotates a full 360° (continuously). That pushes the cyan lever backwards and forwards, rotating the black gear. Which in turn drives the grey gear which is your output. By judicious fiddling with the gear ratio and the crank lengths you'll be able to get just about any output rotation you want.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-17T09:59:18.150Z
Answers.LastActivityDate: 2014-09-17T09:59:18.150Z
Answers.UserDisplayName: Móż
Answers.Body: <p>It would be difficult to get the exact rotations that you are talking about using Power Functions parts. The <a href="http://powerfunctions.lego.com/en-us/ElementSpecs/88004.aspx" rel="nofollow noreferrer">servo motor</a> would be your best option, but its range is fixed to +/- 90 degrees from center. If you use a controller with variable speed, it will rotate through 7 steps to get to 90 degrees in either direction.</p>
  
  <p>If you're willing to look at Mindstorms, there is a servo motor with a built-in rotation sensor that was released with both <a href="http://shop.lego.com/en-US/Interactive-Servo-Motor-9842" rel="nofollow noreferrer">NXT</a> and <a href="http://shop.lego.com/en-US/EV3-Large-Servo-Motor-45502" rel="nofollow noreferrer">EV3</a>. These can both be rotated to and from any position, and they are accurate within 1 degree. It sounds like that's the best option to meet your needs.</p>
  
  <p><img src="https://i.sstatic.net/auB1z.png" alt="EV3 servo"></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-16T12:21:53.153Z
Answers.LastActivityDate: 2014-09-16T12:21:53.153Z
Answers.UserDisplayName: jncraton
Body: <p>I am curios to know if I can utilise the Lego Power range to rotate a transducer to a set point and return to its original position and if so is it able to cycle the movements repetitively? Ideally I would like to set the motor to run  to between say 0 degrees around to 240 degrees and then back to 0, 100 times although these figures could change.</p>
  
  <p>Any advice/help is greatly appreciated!</p>
  
  <p>Thanks</p>
  
Tags: <building><power-functions>
Title: Lego Motor for cycling a tool
UserDisplayName: Mark Poole
ThreadText: # Lego Motor for cycling a tool
  
  (Asked by: username_0 on 2014-09-16)
  
  I am curios to know if I can utilise the Lego Power range to rotate a transducer to a set point and return to its original position and if so is it able to cycle the movements repetitively? Ideally I would like to set the motor to run to between say 0 degrees around to 240 degrees and then back to 0, 100 times although these figures could change.
  
  Any advice/help is greatly appreciated!
  
  Thanks
  
  **Tags:** building, power-functions
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2014-09-17. Score: 3
  
  If you don't need constant speed motion a better idea would be to use a crank running from any modern motor (ie, geared down internally). That way you can guarantee the end points. For a 240° rotation you might need to gear up after the crank, but as long as there's a spring or constant load in one direction backlash shouldn't be an issue.
  
  ![enter image description here](https://i.sstatic.net/eTRKv.png)
  
  Here;s a really quick sketch of what I mean. Your motor drives the black axle in the foreground, and that rotates a full 360° (continuously). That pushes the cyan lever backwards and forwards, rotating the black gear. Which in turn drives the grey gear which is your output. By judicious fiddling with the gear ratio and the crank lengths you'll be able to get just about any output rotation you want.
  
  
  ---
  
  ### Answer by username_2 on 2014-09-16. Score: 3
  
  It would be difficult to get the exact rotations that you are talking about using Power Functions parts. The [servo motor](http://powerfunctions.lego.com/en-us/ElementSpecs/88004.aspx) would be your best option, but its range is fixed to +/- 90 degrees from center. If you use a controller with variable speed, it will rotate through 7 steps to get to 90 degrees in either direction.
  
  If you're willing to look at Mindstorms, there is a servo motor with a built-in rotation sensor that was released with both [NXT](http://shop.lego.com/en-US/Interactive-Servo-Motor-9842) and [EV3](http://shop.lego.com/en-US/EV3-Large-Servo-Motor-45502). These can both be rotated to and from any position, and they are accurate within 1 degree. It sounds like that's the best option to meet your needs.
  
  ![EV3 servo](https://i.sstatic.net/auB1z.png)
  
  
  ---
  
  