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Thread: servo controller with presets AND joystick control

  1. #1

    Default servo controller with presets AND joystick control

    Here is an application that is very close to my need (I'm being a little
    secretive :)
    Imagine a x/y table, or arm, that can grip and pick up a pencil. that is, it
    has two joysticks, one joystick functions in X/Y coordinates on the drawing
    table, the other joystick operates the jaws and lifts the pencil up and down
    on the paper.

    What I want to do is to be able to have 4 preset buttons, each one will set
    down the previous pencil, and pick up a new pencil. (you could name the
    buttons "red pencil", "blue pencil", etc)
    then go to the last position the arm was at on the drawing table.
    Then, I could use the joystick to draw a picture. The complication is, the
    joystick must control direction and speed, NOT ultimate position (Not like
    an RC car, or the analog interface to the SSC that some kind soul
    recommended a couple posts ago.)
    That is, when I let go of the joystick, the movement stops, and stays where
    it is. similar to a control on a backhoe.
    Thanks very much for the input so far!
    regards, Ed Elser
    (funny, this is just a similar application to my main idea, but it might
    provide some entertainment to a disabled person!e)




    >
    >Hi Ed
    >Other than an RC radio I dont know of anything. You need to be a little
    >more specific about what you want.
    >
    >On Tue, 6 Nov 2001 16:52:59 -0500 "Ed Elser" <eelser@s...> writes:
    >> Hello All:
    >> Does anyone know of a stand alone (no PC) servo controller or stamp
    >> program
    >> that allows servo control to two servos via a joystick, as well as a
    >> memory
    >> function, allowing the joystick commands to be memorized into 3 or 4
    >> memory
    >> presets?
    >>
    >> If not, what would it cost to have a program for a stamp written
    >> that would
    >> supply these operations? (I have all intentions of learning basic or
    >> oopic,
    >> but need this application ASAP - sorry If I'm offending anyone...)
    >>
    >>
    >
    Last edited by ForumTools; 10-01-2010 at 06:52 AM. Reason: Forum Migration

  2. #2

    Default

    Servos really only run at one speed. Stepper motors may be a
    better choice. If you are going to use servos then you need to
    read the joystick pots to determine direction AND speed. The
    direction of the joystick deflection will determine whether or
    not to run the servo in a given direction. The amount of
    deflection will control how often you move it in the desired
    direction.

    With your application you need to be able to sequence the servo
    through some number of discrete positions. The more discrete
    positions you can have the smoother the mechanism will operate.
    The maximum number of positions will be determined by the quality
    of the servo and how finely you can control the pulse width that
    determines the positions.

    The direction the joystick is pushed determines which servo will
    move. How far it's pushed will determine how long the system
    pauses between moves. There will be longer pauses with only a
    little stick deflection and they will become shorter the farther
    the stick is moved.

    I wouldn't think you get much total travel out of a servo or are
    you just using the electronics and motor?

    Tim


    ----- Original Message -----
    From: "Ed Elser" <eelser@s...>
    To: <basicstamps@yahoogroups.com>
    Cc: "'Lee Harker'" <harker@a...>
    Sent: Friday, November 09, 2001 8:38 AM
    Subject: [basicstamps] servo controller with presets AND joystick
    control


    > Then, I could use the joystick to draw a picture. The
    complication is, the
    > joystick must control direction and speed, NOT ultimate
    position (Not like
    > an RC car, or the analog interface to the SSC that some kind
    soul
    > recommended a couple posts ago.)
    > That is, when I let go of the joystick, the movement stops, and
    stays where
    > it is. similar to a control on a backhoe.
    Last edited by ForumTools; 10-01-2010 at 06:52 AM. Reason: Forum Migration

  3. #3

    Default

    You can make a servo run slow by incrementing the position just a little bit
    over and over again. Its not super-smooth, but it works.

    On a servo hacked for continuous rotation you vary the speed by sending
    pulses closer or farther from the neutral position.

    ----- Original Message -----

    > Servos really only run at one speed.
    Last edited by ForumTools; 10-01-2010 at 06:52 AM. Reason: Forum Migration

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