Video slider limit circuit

Discussion in 'The Projects Forum' started by deeperrin, Jan 3, 2012.

  1. deeperrin

    Thread Starter New Member

    Jan 3, 2012
    6
    0
    I am working to motorize my video dolly slider (basically a 5 foot rail with a sliding carriage on bearings.) I have purchased the following from servo city:

    • 12v DC Power Supply
    • Servo Controller - has a 5k pot to control direction and speed of the motor
    • Power Control Module - sends the servo controller signal to the motor using two wires (+ , -)
    • Precision Gear Motor - 45rpm
    I would like to design a circuit using limit switches that would stop the motor once it runs to the end of the slider. It would stop once it contacts the switch, but still be able to be reversed using the pot control on the servo controller. I also want to be able to turn the pot on the servo controller and get the motor to run the opposite direction.

    Thanks for any help on this one:
    Derrick Perrin
     
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    What is your question?
     
  3. deeperrin

    Thread Starter New Member

    Jan 3, 2012
    6
    0
    I would like to know where I could find the information on how to design this circuit. I have seen other diagrams on here that will do a motor reverse when the limit is reached but I am looking for it to stop and still have the option to reverse from my controller.

    -Derrick
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,220
    The problem is how to select which limit switch is active and that depends on its commanded direction. I assume that the polarity of the voltage to the motor reverses to change the motor direction, thus you would need to sense the polarity to know which limit switch is operational.

    Do you know the magnitude and type of signal going to the motor? It's likely a PWM signal that would have to be filtered to determine its polarity. What is the make and model of the controller and servo you purchased?
     
  5. deeperrin

    Thread Starter New Member

    Jan 3, 2012
    6
    0
    Thanks for your help.
    I am using a 12v dc power to my Precision Gear motor. It is being supplied by a Precision Digital Speed Control connected to a Dual Servo Driver all from Servo City. The Sual Servo Driver is supplying the PWM via a 3 wire connection to the speed controller. The controller then has a two wire connection to the Motor. A polarity change will change the direction of the motor.
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Do you want it to stop when it hits the limit switch, reverse when it hits the limit switch, or reverse at a slower speed when it hits the limit switch?

    Are you thinking of something like a remote control setup where you can go forward and backward at various speeds, but have the limit switches prevent it from running off the rail?
     
  7. deeperrin

    Thread Starter New Member

    Jan 3, 2012
    6
    0
    I have a controller that has a 5k liner pot on it. I turn it one way and the motor runs in one in one directioin and then turn it the other way and it will run in reverse. I would like it to get to the end of the rail and stop. When I turn the pot to the other direction it would then run to the other side. When it starts moving to the other side it would deactivate the switch and allow me to move in either direction.

    Thanks for the help today-
    Derrick
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Do you want this to be a remote control?

    Wired or wireless?

    Do you have any experience with microcontrollers?

    A better method would need to be devised for this that will somehow integrate into the controller you already have purchased. They have a Joystick to use instead of the R/C PWM input you are currently using, though it is a bit spendy. A microcontroller creating the PWM while checking limit switches would be the most straightforward method.

    --ETA: The Servo Controller is already a PIC microcontroller sending the PWM based on pot inputs. Writing a new program and plugging in a different uC could read the potentiometer in addition to the limit switches, and could "fix" all your problems with some program changes and a couple limit switches.
     
    Last edited: Jan 4, 2012
  9. deeperrin

    Thread Starter New Member

    Jan 3, 2012
    6
    0
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    What I was suggesting, was that Dual Servo Controller is based on a Microchip PIC microcontroller.

    Run the wires from the limit switches into that box, and plug in a new controller PIC IC of the same part number (should be 16Fxxx or 16Cxxx) to add the functions you want to it. This would require some programming in C or BASIC and a programmer, but one of the people around may be interested in writing the code for fun.

    This would be the "minimum modification" route for what you'd like to do, changing the firmware on the box you are currently using to integrate limit switches.

    Now, it's a matter of whether or not you are comfortable with that method.
     
  11. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    2 diodes, 2 normally closed limit switches
    [​IMG]
     
  12. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,220
    I like it.;)

    Can hardly get more simple then that.
     
    strantor likes this.
  13. deeperrin

    Thread Starter New Member

    Jan 3, 2012
    6
    0
    Thanks for the diagram I will try that out.
     
  14. Feankie1331

    New Member

    Dec 13, 2015
    7
    0
    Try the Cheeseycams solution. Good luck
    http://cheesycam.com/redrock-micro-one-man-crew-kessler-parallax-slider-10-diy-version/
     
Loading...