How to build circuit for lifting mechanism

Discussion in 'The Projects Forum' started by kksmith, May 23, 2009.

  1. kksmith

    Thread Starter New Member

    May 23, 2009
    5
    0
    Hi,
    I need to build a simple machine which can work on DC battery but I have no knowledge of electronics may be someone can help me.

    Task: I need to move a small platform up & down for hobby project. If I press switch upward it should go up and if I press switch downward then platform should move downward.

    Problem:
    I can build up mechanical setup but I don't understand how to control motor turn clockwise and anti-clockwise with a switch. Second problem is once it reaches to the extreme limit how to stop motor automatically.

    Any help or pointer to right direction would be highly appreciated.

    Thanks in advance.
    Kevin
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    What is distance from floor to platform, retracted? Now extended? What is size of platform? What load must it lift?
    One option is a scissor jack, using a gear-speed reduced electric motor, threaded shaft, nut two limit switches, & a DPDT relay; also the up-dn switch.
     
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,674
    899
    The simplest, non-electronic method would use a reversing switch and two limit switches.

    The reversing switch can be made from a DPDT switch. I would suggest one with center off. I can't draw you a schematic right now, because that computer has a problem. The two power leads go to the two center terminals. The motor leads go to one set of the outer terminals, and two wires crisscross to the other set of outer terminals. Just look up how to wire a reversing switch. An alternative to a toggle switch is a push-button switch. Commercial versions can be quite expensive, if bought retail. You want a lock-out switch, so you can't push up and down at the same time.

    Limit switches are self-explanatory. They simply switch off the power when the lift moves the actuating lever.

    John
     
  4. loosewire

    AAC Fanatic!

    Apr 25, 2008
    1,584
    435
    How much weight,are going verical up and down,a little more Information.
    Does It have a mechanical part to It.
     
  5. kksmith

    Thread Starter New Member

    May 23, 2009
    5
    0
    Thanks for quick replies, it's not very heavy to lift.
    Scissor type jack system can work well.
    It needs to move about 80mm and weight is approx 300 grams.

    I looked at computer cd mechanism which is perfect example what I need. I can pull out cd tray from old computer but I need to run on batteries so that I can easily take to different places without worrying about power supply.

    Thanks
    Kevin
     
  6. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi.

    I have just built a system that does just what you require. It was for an award ceremony and it had to lift trophies up and down.
    I used a PIC16F877 Microcontroller running at 4Mhz. The motor was PWM controlled so that the speed up and down could be set and limit switches did the business of stopping in both directions. It had an up, down and stop switch and would automatically move to the up possition on start-up.

    If this would help you, I could let you have all the details and PCB layouts, and could progam you an 877 if you can not do it yourself.

    Where are you?

    I am away for a week on holiday, so I can not do anything and have no internet connection until I get back next Saturday.

    Daniel.
     
  7. kksmith

    Thread Starter New Member

    May 23, 2009
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    0
    Hi Daniel,
    It seems to be you're the right person with all the details what I need.
    It would be really great if you can arrange circuit layout for me. There is no rush you can take your time. I'm based in Australia.
    Cheers,
    Kevin
     
  8. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi there,

    I am back now. I will sort out what you need and post you the details within the next week or so.

    Daniel.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you just want something really simple that consists of just a DC motor, a DPDT (Double Pole Double Throw) toggle switch and a couple of NC (Normally Closed) limit switches, you could use this:

    [​IMG]

    S1 is the DPDT switch.
    S2 and S3 are the limit switches.

    There is no braking provided with this circuit, so the motor will take a moment or two to stop.
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    My thought was a servo with (you guessed it) a 555 driver. I like the previous thoughts more though.
     
  11. kksmith

    Thread Starter New Member

    May 23, 2009
    5
    0
    I'm bit stuck at mechanical lifting mechanism at this stage. I built up simple scissor type lifting system and used toy motor. It works fine but I'm not very satisfied with the results because of excessive friction.

    Now I'm inclined towards CD tray ejection system which I can directly connect to my lifting object.

    My question is: Can I run cd ejector assy with battery?

    Thanks
    Kevin
     
  12. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    does it need to be self holding at any position?
    can the platform travel along a vertical support, or must everything be below the platform?
     
  13. kksmith

    Thread Starter New Member

    May 23, 2009
    5
    0
    It doesn't need to stop in-between. If it stops on topmost and lowest point I'm happy with that.

    I'm thinking to use kitchen drawer slides to support and move unit up & down. It doesn't matter if lifting mechanism protrudes above the platform.
    Kevin
     
  14. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    Kind of overkill for 80mm.

    That old bubble jet printer your ready to throw out, or some else's. Rip that puppy apart and extract the tub traversing mechanism. You'll find a great linear drive system that with a bit of modification will accept your platform. The drive motor will be stepper, but if you want you can replace it with a gearmotor, as you will certainly need some speed reduction/torque multiplier. Should even have limit switches.

    Depending on you skills, you may want to keep the stepper, maybe even some or all of the controller to hack away.
     
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