Simple way to get motor to reverse.

Discussion in 'The Projects Forum' started by GunsNTulips, Dec 21, 2013.

  1. GunsNTulips

    Thread Starter New Member

    Nov 22, 2013
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    I have a motor that drives a pen back and forth. I would like to hook it up so that I can control it with a simple joystick. It is a basic Atari 2600 joystick, so it just has simple buttons for each direction. Reversing the motor is easy enough, but I can't figure out one circuit that will reverse polarity depending on which button is pressed.
     
  2. #12

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    Nov 30, 2010
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    LOL! You must be young.:)
    My father didn't understand TV or refrigeration and you called something a, "simple joystick".

    That being said, I leave you to the tender ministrations of the guys and/or gals that know the answer. I just wanted to thank you for the morning LOL.
     
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  3. MaxHeadRoom

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    Jul 18, 2013
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    The J.S. appears to be contact closure on L-R-U-D on D connector pins 1 -4 and 8 being common.
    So you could use a couple of small DPDT relays that are picked up by two of the switches.
    I have no personal experience with the J.S. just what schematics are out there on the web.
    http://www.epanorama.net/documents/joystick/ataristick.html
    Max.
     
    Last edited: Dec 21, 2013
  4. GopherT

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    Nov 23, 2012
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    Look up H-BRIDGE for your circuit configuration - it allows motors to be reversed. The motor fits in the cross of the "H".
     
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  5. GunsNTulips

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    Nov 22, 2013
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    H-bridge is perfect. Now I need to understand transistors beyond the academic knowledge I have.
     
  6. GopherT

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    What amperage and voltage are the motor?
     
  7. MaxHeadRoom

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  8. GunsNTulips

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    Nov 22, 2013
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    Honestly, I don't know yet. My dad is bringing me an old XY printer. I'm kind of making assumptions about its design. It's old enough that any real interface with it is unlikely, but I think I can have fun with the XY actuator.


    I figured when it it came down to controlling speed, i would use a PWM circuit. (Which now I see is what you linked to MaxHeadroom).
     
  9. MaxHeadRoom

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    Most printers use stepper motors, you mentioned in the OP you have a motor already?
    If so what technology is it?
    Max.
     
  10. GunsNTulips

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    Nov 22, 2013
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    I don't know. It is a very old XY printer. I would be afraid to make any assumptions about what it is. I will be taking it apart sometime next week. If it is a stepper motor, I'll have to design around that. Given that the eventual long term goal is a sort of 3D printer, that may actually be a blessing. At the moment, I just want to demonstrate control over the print head. The 3D printer is years off.
     
  11. #12

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    Stepper motors are marvelous things for this sort of job. So much more accurate to control than anything else.
     
  12. MaxHeadRoom

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    Not quite true in all senses, the stepper can only position to the nearest step.
    Servo's are practically infinite by comparison, depending on the resolution of the encoder, (least input increment).
    Max.
     
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  13. GopherT

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    Old HP plotters used brushed DC motors with encoders on the back end - I think 512 pulses per revolution on a quadrature encoder. The motors will likely be equipped with encoders or they will be steppers based on all of the printers and office equipment I have dealt with.
     
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  14. #12

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    Well, 512 is a lot more than the number of poles in any stepper I have ever seen.
    My distorted point of view is that I used to work on automatic lasers and they were geared down so far that the resolution was beyond my imagining. Something like three quarters of a turn to correct the beam by 1/8 inch at a hundred yards.

    It is possible to gear down a stepper motor for a 3D printer, but I don't know if that's how they do it.
     
  15. MaxHeadRoom

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    Actually 512 is a rather low resolution by modern standards, even when the quadrature pulses are multiplied by x4 by counting each rising and falling edge, 512 x4 = 2048 pulses/rev.
    It is not uncommon to see 100kcounts/rev on modern CNC systems.
    Max.
     
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  16. GopherT

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    The problem is that they coast whereas stepper motors have built-in braking.

    Stepper moters is exactly how they do it in 3D printers except that they are direct drive (1:1) - not geared for x-y movements. A screw is used for z-axis if you want to call that a gear ratio.
     
  17. djsfantasi

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    A .9 degree stepper motor has 400 steps. Using a micro stepping controller, this resolution can be dramatically increased at the cost of torque and power requirements. I've only experimented with steppers, but used half stepping on a 1.8 degree stepper motor to get 400 steps for a robot. Apparently 400 step motors are available (Google "how many steps in a stepper motor").

    But this is in full step mode. I used half step mode, and when checking that my memory hadn't failed me, found the subject covered when Googling for "micro stepping".

    Hope this helps.
     
  18. GunsNTulips

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    Nov 22, 2013
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    Technically, it is a plotter, not a printer.
     
  19. MrChips

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    You can avoid a lot of confusion if you stated the make and model of the XY plotter.

    Yes, micro stepping controller will give you many more steps and perfectly doable.
     
  20. GunsNTulips

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    Nov 22, 2013
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    Well it looks like the printer is not at all what my dad had described to me. It is a Mettler GA15 plotter. It does not have an XY motor, although it is not a step motor. I'll need to find another use for it though.
     
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