Sticky Servo - Is there such a thing?

Discussion in 'The Projects Forum' started by squatchy, Nov 21, 2012.

  1. squatchy

    Thread Starter Member

    Nov 21, 2012
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    I'm imagining a servo which can "remember" its position. It would come with an attached circuit which cycles this remembered frequency to itself until otherwise signalled.

    The method of sending an updated value to the servo helper could be varied (digital serial?), but for starters I'm wondering if there's a nifty circuit simply for remembering (and self-generating) an adjustable frequency.

    Any help?

    Yes I'm new, yes I googled, and yes I lurked. :)
     
  2. John P

    AAC Fanatic!

    Oct 14, 2008
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    You don't seem to have directed your googling toward hobby servos, or you'd know that they aren't controlled by a frequency, but by a pulse width. It's explained here:
    http://www.princeton.edu/~mae412/TEXT/NTRAK2002/292-302.pdf

    If you want to generate a servo control signal that doesn't change after a shutdown and restart, you need a microcontroller. With that, it's easy. With anything else, pretty difficult.
     
  3. squatchy

    Thread Starter Member

    Nov 21, 2012
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    Couldn't you somehow rig a digital potentiometer (which can take in a single signal then remember its resistance value) with a servo and a timer in such a way that the timer keeps sending the same pulse width (based on the digpot) to the servo until updated by another signal sent from the controller?
     
  4. John P

    AAC Fanatic!

    Oct 14, 2008
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    A digital potentiometer, I had not thought of that. Yes, you could do what you say. But you'd need the unit itself, plus an analog circuit to generate the pulse and use the pot's output to make a pulse width (which might not be accurate over time), and you'd need to have a programmed processor available to input the data. By the time you'd done all that, why not just get a cheap processor as the only component?
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    There are also plenty of 555 circuits that will do the same thing. Look up animatronics as a search word.
     
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