help with controlling servos needed

Discussion in 'The Projects Forum' started by eoa, Nov 10, 2013.

  1. eoa

    Thread Starter New Member

    Nov 10, 2013
    2
    0
    Hello,
    some time ago i bought a couple of "robotic kits" which consisted of an spindle controller, circuit board and a servo. i'd like to use both servos in a project i'm working on however my electronic knowledge is a bit rusty (the last time i did something like this was over 25 years ago in school). currently i'm working on making a model eye with 1 servo operating the eyelid and the other servo moving the eyeball (weird as it may seem but it's for a costume).

    the first problem i've encountered so far is that when using both servos they started jittering but when i unplugged one the other worked fine. also with the battery, circuits and controllers, the box that houses them all seems to be a little too bulky to fit comfortably in my pocket.

    so my question is this would it be possible to run both servos off of 1 controller with the help of adding 3 way switch and if it is possible, is there somewhere i can get instructions on how to wire the 3 way switch, looking at them on-line they look quite confusing to connect up

    many thanks
    graham
     
  2. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Welcome to AAC.

    There are a number of reasons this could be happening. First and foremost, do you have a schematic or a link to the circuits you are using? Second, is there any wireless control involved?

    Certainly possible, but we need to "see" what you're working with. Again, a schematic would help. Failing that, take some good, clear pictures of your circuits and servos and post them here and we'll see if we can help.
     
  3. eoa

    Thread Starter New Member

    Nov 10, 2013
    2
    0
    hello and thanks for your reply, the only schematics i have are these :

    [​IMG]

    [​IMG]

    also here's a closeup of the circuit board

    [​IMG]

    many thanks
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Some (cheap) servos have internal backlash between the gear motor and the position sensing pot, and they just "buzz" trying to null out the error...
     
  5. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    So you have two circuits, two pots, and two servos and, I assume, used the same battery pack to power both circuits? If yes, the problem may simply be noise generated by the 556 (which are inherently noisy). As a check, have you tried powering each circuit with the battery pack, one at a time only, to verify each circuit and servo is working correctly?

    I see a small capacitor across the power leads, but not a big one. You might try adding a 1uF electrolytic capacitor across the power/battery leads on each circuit board.

    If you still want to use one circuit for both servos, I can draw up a simple diagram showing how. I'd suggest a DPDT switch and disconnecting + power and the signal from each servo. Only disconnecting one of these may cause the servo to move out of position or jitter, but I'm not sure.
     
  6. BobTPH

    Active Member

    Jun 5, 2013
    782
    114
    A servo will not hold postion unless it is powered and receiving a valid signal. So running 2 off 1 controller seems unlikely.

    Bob
     
    elec_mech likes this.
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