Any Suggestions on how to design a circuit to put a motor on a timer?

Discussion in 'Digital Circuit Design' started by thetered, Oct 12, 2016.

  1. thetered

    Thread Starter New Member

    Oct 12, 2016
    1
    0
    Hi! First off I'm trying to design and build a circuit or device that will allow me to move an item from one end of my yard to the other, sit there for a few minutes then return to the other side. So if you can think of a different or better idea than I am proposing I am all ears.

    But what I'm thinking is on one end a pulley and the other end the motor and a string looped around them and the item hanging from the string, the item is light, less then half a pound. The motor would turn on spin the the string pulling the item to one side, stop for a few minutes and then return it, but for that to work also the polarity of the motor would have to reverse. I'm including a crude drawling to show what I am proposing, but knowing what the goal is if you have a better or more simple idea, I am all ears. Thanks!

    couch.jpg
    http://imgur.com/JcHJ8jz
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
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    You most likely need two limit switches and reversing relay, and a timer plus a stop/start P.B..
    What voltage is the motor, is it weatherproof if kept out doors?
    Max.
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    With careful mechanical design you could avoid the need to reverse the motor by copying the ski-lift principle, with a pivoted support for the object on an endless loop.
     
  4. James55

    New Member

    May 29, 2016
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    Have you thought about using an H Bridge motor controller?

    You can have fun and build your own, or you could just buy a pre-made module like the L298N and plug it into an Arduino.

    That would be a cheap and relatively simple option.
     
  5. ci139

    Member

    Jul 11, 2016
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  6. drc_567

    Member

    Aug 23, 2016
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    A simple string construction presents several problems such as sag, weathering, being an obstacle, if it is not sufficiently high. What is the distance of your traverse? Maybe by using two lengths of angle iron, paired together, you could form a track of sorts to provide a channel for a carrier. Then use a motor at each terminal to supply the necessary tensile force on a fiber or wire. Is the 'stand still' time of the load a constant value, or would that need to be adjustable?
     
  7. WBahn

    Moderator

    Mar 31, 2012
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    Yes. Clearly a simple and obvious solution for someone that wants to move something back and forth across their yard.

    Notice that, even if they were to adopt this approach, it fails to satisfy their goal of having the object stop and stay at each end for a period of time. The cars on a detachable lift continuously move.
     
  8. WBahn

    Moderator

    Mar 31, 2012
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    As with most things, there are a number of solutions. Using a bi-directional motor with limit switches and an H-bridge to drive something like a permanent magnet DC motor is probably the easiest and cheapest.

    Depending on the layout there are other options. If it is relatively short you could use a counterweight at the far end and use the motor to pull the object in one direction and then let the weight pull it the other. You could do something similar using a spring, but that would be for even shorter runs. My guess is that the distance implied by "across the yard" make either approach non-practical.

    If you didn't need it to stop at each end then designing it so that the object's attachment point can go around the pulley has a lot going for it. Even so, that might still be a good approach because no you don't have to reverse the motor, you just need to detect that the object has reached the middle of the pulley and pause the motor for a set about of time.
     
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