Electromagnet triggering an indicator

Discussion in 'The Projects Forum' started by copucopu, Jun 3, 2014.

  1. copucopu

    Thread Starter New Member

    May 26, 2014
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    I trying to be creative in my free time so i am making an indicator which is triggered with an electromagnet :p.
    I basicly have a plastic circle with a magnet glued on it. On the other side I have an electromagnet, and when current passed through the electromagnet it pushes the magnet glued on the circle(and with the help of some gravity).
    The indicator when not triggered shows green field and then when triggered shows red..

    It works fine...But do you maybe have an other idea for triggering with an electromagnet or maybe a complete redesign of the indicator...
    Because if you shake the housing, sometimes the magnet drops away from the electromagnet when no current is passing through...
    I am using an electromagnet from an relay...

    I am always looking for improvements :)

    One bad sketch...
    [​IMG]
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    You sketches are fine. It's your written description that sucks. ;) (friendly teasing)

    Ok, if the "circle" rotates on an axle we call that a "rotor". The electromagnet is part of the "stator" (part that doesn't rotate).

    I'm assuming the goal of the thing is that the electromagnet pulses at the right time, and makes the rotor keep spinning?

    We call that "commutation" and it means switching on the power to the coil, only when the rotor is in the correct position.

    If you want to perform electronic commutation and make it spin, you can use a light sensor or magnetic sensor that detects the rotor position, and turns on the coil when the rotor is in that position.

    It's basically the same deal if you don't want it to spin continuously but just turn back/forth.

    It will REALLY help if you provide info on what this is supposed to do, and photos can save a thousand more words too. :)
     
  3. copucopu

    Thread Starter New Member

    May 26, 2014
    21
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    its meant to change only from green to red. and stay there.
    First it shows geen colour, and when an pulse occoures it only rotates to red. that is all.
     
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Ahah! Thanks for explaining.

    You will have a very difficult time getting 90 degree rotation from one coil and one rotor magnet.

    My suggestion would be to put the rotor disc on the end of a tiny DC motor, like a toy motor.

    Then use mechanical stops on the disc, to limit movement to 90 degrees.

    Then just drive the motor with either polarity, that will rotate the disc until it hits the stops.
     
  5. copucopu

    Thread Starter New Member

    May 26, 2014
    21
    1

    Thank you for your ideas.

    I already have a mechanical stop on the disc.

    I am looking for a better triggering solution insteed of a electromagnet+magnet
     
  6. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Have you considered an RC servo? Simple controllers can be made with two 555s.
     
  7. copucopu

    Thread Starter New Member

    May 26, 2014
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    I am looking for a simple solution...
    But I want it to still remain electromechanical... Maybe some other electromehanical solution + the help of gravity (This indicator will be always positsioned portraid.)
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Perhaps use a model motor with a string wound on the shaft to pull a release pin?
     
  9. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Or even simpler, use a solenoid whose plunger is engaged with the reverse of the indicator. When energized, the indicator can move. Weight the indicator so that gravity will rotate the indicator 90°.
     
  10. copucopu

    Thread Starter New Member

    May 26, 2014
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    Sounds like a good idea.
    A sketch would be appreciated, or maybe a more detailed description.
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    Have you googled flip dots?
     
  12. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I've tried to make a sketch. Note that while I show a hole for the solenoid pin on the front of the indicator, it is not necessary; I included it to show how the solenoid would operate.

    So in a set state, the solenoid plunger would engage in a socket on the indicator circle. You may need a push/pull solenoid in order to engage it. Or if you extended the plunger with non-magnetic material out the back, you could simply push the plunger into place. The socket could be as simple as a bottle cap glued onto the back, as long as there is sufficient clearance for the bearing frame.

    The weight should be placed so that when it is in the down position, the correct color is shown. Your indicator design of quadrants implies that the weight should be 90 degrees to the vertical rest position.
    [​IMG]
    A pulse to the solenoid will retract the plunger. Now with nothing to hold the indicator in its current position, gravity will take over pulling the weight down 90 degrees. This will change the indication.

    Will this work for you?
     
  13. inwo

    Well-Known Member

    Nov 7, 2013
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    4 magnets near axle would make it balance. Alternate polarity NSNS.

    The iron core of two electromagnet should hold position when not energized.

    Reversing polarity resets.

    A manually commutated motor?
     
  14. copucopu

    Thread Starter New Member

    May 26, 2014
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    Actually I get it...

    But these would be a more expensive solution... If you compare the electromagnet+magnet VS solenoid = 1:10 (at least)
     
  15. copucopu

    Thread Starter New Member

    May 26, 2014
    21
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    But anyway good idea.
    I`ll give it a try.

    And still open for new ideas.
     
  16. inwo

    Well-Known Member

    Nov 7, 2013
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    Have you thought of a simple bell crank linkage. It's esy to get well over 90° from a solenoid.

    [​IMG]

    [​IMG]
     
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