Hobby Servo or Dumb Servo

Discussion in 'The Projects Forum' started by steadicam1, Jan 15, 2010.

  1. steadicam1

    Thread Starter New Member

    Jan 15, 2010
    3
    0
    Hello All

    This is my first post. Also i am not an electronics guru nor a servo guy I can read schematics and use a soldering iron...I am looking for a circuit to drive a hobby servo or a dumd servo (5 wires and a "pot") with a potentiometer (5 or 10k) with adjustable stop limits (pref. pots) on the throws in both directions.

    This project is for a focus motor on a camera lens of a TV Camera the barrel of the lens for focus has diffent travel from lens to lens hence the need for adjustment.

    All help is appreciated!!!!

    Erik
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Is this an actual RC Servo or one you are making up? Most RC Servo's I have worked with only have 3 wires (+V, Signal, and Ground), and the pot is built into the gear drive mechanism so the on board controlling circuitry knows what "position" the servo is at.

    If you use a regular RC servo, you can use a 555 timer to supply the pulses to move the servo left or right with a potentiometer..... Check out this site for more info on controlling an RC servo with a 555 timer >>> http://www.horrorseek.com/home/halloween/wolfstone/Motors/svoint_RCServos.html#Driving

    My .02
     
  3. steadicam1

    Thread Starter New Member

    Jan 15, 2010
    3
    0
    Thanks for the reply that info may help...and yes i am using a servo motor with just a potentiometer attached to it no circuitry just 5 wires and it needs 12 VDC...so if anybody can point me in the right direction thanks
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    Those types of servo connections are basically the "cheap" servos that you can find in a remote control RC car setup (might not be exactly the same application as your motor, but similar), they still require the same controlling circuitry as a regular servo motor, except the control circuitry is usually built as part of the receiver, this setup is usually used in steerable rc cars, and this motor/pot combination is used for that.

    an "open loop" servo controller might do the trick, but a closed loop system might be better, you will need some circuitry to control an H-Bridge (such as the (LMD18201T)and some kind of PWM generator circuit (can be based on a 555 timer) for motor speed control. By the time everything is said and done, you might be better off using a microcontroller to do the motor control, use one with a couple of ADC inputs and PWM output capability (or generate PWM by code using timers and interrupts). Use the pot as an input to one of the ADC's to determine motor position, you will only need 3 pins to control an H-bridge such as the one I mentioned, (Brake, PWM, and Direction).


    My .02
     
  5. steadicam1

    Thread Starter New Member

    Jan 15, 2010
    3
    0
    BMorse

    Thank you for the info and I dont mean to be a pain but if you can kinda give me specific model numbers and circuits I would very much appreciate it as i have said I am a novice but with a little instruction I can do.

    Also would I be able to control end limits with what you are speaking of?

    I really appreciate your time as I am having no luck anywhere else!!!
    erik
     
Loading...