reverse and forward motor control for AC motors

Discussion in 'General Electronics Chat' started by Cristopher Tingcang, Jul 31, 2011.

  1. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    Good day to all!!!

    I am an electronics engineering student. i just want to ask if anyone here knows what is the best motor that i should use in my thesis. it is all about automated clothes line with rain and temperature sensor. I am not that sure how to incorporate or control the direction of the rotation of the motor. The load in the clothes line should be at least 100 lbs. i hope that somebody can help me about this.

    Thank you!
    :)

     
    Last edited: Jul 31, 2011
  2. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    Good day!!!

    I am an electronics engineering student. I am having a thesis right now. It is all about automated clothes line with rain and temperature sensor. Our professor suggested to us that the study should be improved more so we decided that the user can set the amount of time that the hung clothes should be exposed to the heat of the sun. I just to ask your suggestions of what timer should I used. I am planning to use countdown timer. Could it be good?...

    Your suggestions will be very much appreciated.

    Thank you!!!

    :)
     
  3. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Do you have to control the speed of the motor?

    It's easier to control the rotation direction of an DC motor than of a three phase AC motor, especially if you need to control it's speed.

    Also, what voltage do you want to work with?
     
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  4. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    You need to give us more information so we know how to incorporate a timer in your design.

    Post some schematics etc.
     
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  5. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    Thank you for your suggestions!

    I am planning to use 110V AC for the motor. I have read in one of the books that AC motors do not need much maintenance compared to DC motors. The speed of the motor should be enough to move the clothes line on the covered area immediately so that the clothes will not get soak from the rain.

    A professor of mine told me to use contactors to control the forward-reverse rotation of the motor. Is it good to use this?

    What are other alternatives to control the rotation of the motor?

    Thank you!

    :)
     
  6. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Other alternatives are frequency inverters.
    You didn't answer but I guess you don't need to control the motor's speed.

    Will the motors be monophase or threephase AC motors?
     
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  7. #12

    Expert

    Nov 30, 2010
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    Where would he get 3 phase 110 volt motors and why would he choose them?
     
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  8. praondevou

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    Good point. Maybe I should have read his message with more attention..:D
     
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  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Most single phase AC motors are run in one direction only. Getting them to run backwards requires some special electrical 'surgery' and wire cutting to install a switch. And after all that, they won't run very well in the backwards direction because they are designed to be very efficient in running the other way. Changing directions negates all the special designs that the engineers included to create such high efficiency.

    I suggest a simple toggling gear box that will engage the shaft with one gear, and with the help of a solenoid plunger engage another gear pair for reverse. The motor will always turn the same direction and your reverse switch will just 'push' a different gear into mesh with the motor shaft. This will also allow you to select a better final speed output for reeling in/out the clothes line, since the 1800/3600 rpm of the AC motor will be a little to fast for good control of the process.
     
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  10. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Yes.
    So your options are:

    - Kermit2's surgery
    - DC-motors
    - buy a reversible single phase AC motor like these

    IMO, the best option is a DC-Motor.
     
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  11. #12

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    I buy reversable AC motors for single phase 230V every week. They can be reversed by switching 2 wires, perhaps with a DPDT switch or equivalent. Unfortunately thay are 850 to 1075 RPM fan motors with little or no starting torque.

    Easy reversing is available. The gearing is what will be costly.
     
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  12. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    Thanks again for a very helpful answer.

    I am really confused right now. You are suggesting that I should just use DC motors. How much load can a DC motor manage? I think I need to read a lot about motors. Thank you for your help. What is the operation of a 3-phase motor? The required voltage and how to convert the voltage source from the outlet of the house into three-phase.

    Thank you!!!

    :)
     
  13. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Forget this, you need an inverter for this, gets much too expensive. I didn't mean to create more confucion. You probably won't find a 3-phase AC motor for 110VAC (that would be custom made). They usually are made for 208V 3-phase power or more.

    Stick to your reversible motors or DC-motors.
     
  14. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    Thank you for sharing your knowledge...

    I have found my answer.. I will be using a capacitor run, single phase motors. I have read that they are reversible through the use of capacitor. What I will need now is to study its operation when it is applied in my project since my project is automation using microcontrollers..
    Do you have any suggestions?

    Thanks a lot!!!
     
  15. iONic

    AAC Fanatic!

    Nov 16, 2007
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    You might find that many of the Brushed DC motors downfalls might be insignificant in the application you describe. Use of the micro controller and PWM the speed of the line in either direction. Brushless DC motors are very efficient. I would venture that a 12V battery and a solar panel could operate this device for a long time.
     
  16. BillB3857

    Senior Member

    Feb 28, 2009
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    Look into a garage door opener. It does almost what you want.
     
  17. iONic

    AAC Fanatic!

    Nov 16, 2007
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    100lbs of cloths is a either a very long cloths line or some sopping wet cloths or both. You may think that you will need a motor with 100lbs. of torc but since the cloths are on two pullies you will not be lifting the cloths, just moving them horizontally.

    A garage door opener, while it offers forward and reverse and has a very slow RPM could work well in your project, but it is a large motor, much larger than necessary.

    Also to be considered is the length of the cloths line. It will need to be double the length of an average line as you need to move it untouched underneath a covered space. This will cause the line to sag a great deal more and significantly increase the force on the two end poles holding the line of cloths.
     
    Last edited: Aug 10, 2011
  18. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    Thank you!!!

    Can you suggest then the load that 110V Single phase AC motor can drive?
    And do you have schematics for the garage door opener. I am very glad that you are sharing your knowledge about this topic.

    Thanks!!!
    :)
     
  19. Cristopher Tingcang

    Thread Starter New Member

    Jul 31, 2011
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    I am planning that I will construct a clothes line that has 3 lines to shorten the length of the lines and the weight of the clothes will be distributed evenly. It will be supported on both ends by steels/iron. Next time, I will attached the image of my planned design of the clothes line. Will you please evaluate those plans for me to find out the loopholes and the things that should be considered.

    Thank you!
    =)
     
  20. strantor

    AAC Fanatic!

    Oct 3, 2010
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    keep in mind, with every line you add, you increase the load on the poles. the load is multiplied when not hanging straight down. the sling angle factor for a 5 degree angle is 11.5; approaching 0 degrees, it would be closer to 12. hanging 100lb in the center of a taut line will present a 1200 side-load on the poles. 3 such lines will be 3600 lbs.

    http://www.cicb.com/products/inspector-tools-and-forms/sling-angle-factor-card.html
     
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