Need help with building electromagnet lift

Discussion in 'General Electronics Chat' started by Nagah, Apr 11, 2015.

  1. Nagah

    Thread Starter New Member

    Apr 11, 2015
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  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is how a typical lift/material handling magnet appears, what is the resistance? Did you try it on an automotive battery or higher capacity?
    Typically when used as a lift magnet, it requires a reverse polarity shot also to demag.
    Max.
     
  3. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    If it is of the PM/EM variety you will see (significant) 'force' only when the device is not energized...

    Best regards
    HP
     
  4. Nagah

    Thread Starter New Member

    Apr 11, 2015
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    Does that mean, I charge the device for a long time before I can see the effect?
     
  5. paulktreg

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    What sort of battery are you using?
     
  6. Nagah

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    Apr 11, 2015
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  7. MaxHeadRoom

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    ...Again What is the resistance of the magnet??
    Max.
     
  8. Hypatia's Protege

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    Mar 1, 2015
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    No... If it is indeed a PM/EM (i.e. permanent magnet/electromagnet) unit it will attract ferrous objects without power applied, whereas application of power (of correct polarity and current) will effectively 'cancel' its magnetic field. ----- On the other hand if the device is solely electromagnetic it will show only slight (residual) magnetism while non-energized, but become strongly magnetic with the application of power...

    To summarize:
    PM/EM: Power on => Magnetic field 'OFF'/ Power off => Magnetic field 'ON'
    EM only: Power on => Magnetic field 'ON' / Power off => Magnetic field 'OFF'


    BTW that's a very low capacity battery for your application!:eek:
    It may not supply sufficient current for even brief operation -- in any event it won't last long... As per posts Nos 2 and 7 you should ascertain the coil resistance such that you will be cognizant of the current/power requirement..

    Best regards
    HP

    PS: Please note that the eBay description of the magnet implies a current requirement of 250mA and, hence, a (nominal) resistance of 48 ohms...
     
    Last edited: Apr 12, 2015
  9. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    The solenoid requires 250mA @12V, you will not get anywhere near this current with that tiny 12V remote control battery.
     
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  10. Nagah

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    Apr 11, 2015
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    Thanks so much. I will get a 12V battery with higher capacity and report back.
     
  11. MrChips

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    Oct 2, 2009
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    In order to lift a ferro-magnetic object the magnet must come in direct contact with the object. Only then will you experience the maximum lifting capacity.
     
  12. MaxHeadRoom

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    This is an example of the cranes I designed electronics for!

    As the magnet heats, the magnetic strength decreases.
    Max.
     
  13. Nagah

    Thread Starter New Member

    Apr 11, 2015
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    Fabulous. This is the kind of thing my son wants to build for his science project. Do you have any tips on how to build a model version of this for his school project?
     
  14. MaxHeadRoom

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    Jul 18, 2013
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    A very simple relay for the pick up condition, you may need a short reverse demag pulse if light objects stay attracted at the point of turn off/drop.
    Max.
     
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