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Electromagnet project

Discussion in 'General Electronics Discussion' started by Blu35tarsix, Jan 26, 2017.

  1. Blu35tarsix

    Blu35tarsix

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    Jan 26, 2017
    Is there an easy way to get a set of 18 electromagnets (probably 12v 2a each) to fire in a programmed sequence for certain durations and also reverse polarity? Would it be something a newbie could put together with some help or something I should outsource?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Controlling the magnets is the "easy" part. You can use relays or transistor based H-bridges whcih you can buy off-the shelf if you are uncomfortable rolling your own.
    Where would your "programmable sequence" come from and how do you envision to program the sequence(s)?
    A small microcontroller like e.g. an Arduino or a more powerful Raspberry Pi can be used. How well honed are your programming skills?
     
  3. Blu35tarsix

    Blu35tarsix

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    Jan 26, 2017
    Not much of a programmer but I'm sure I could read enough to figure it out. Do you have a suggestion for a way to hire someone to draw up a schematic that I could put together myself?
     
  4. Alec_t

    Alec_t

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    Jul 7, 2015
    Welcome to EP.
    I'm sure the forum members can provide a schematic without you having to hire anyone, once you've decided whether you wish to use off-the-shelf modules as far as possible or go for a more component-level approach.
     
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Actual circuitry as well as the "electromagnets" you plan to use will depend a lot on the timing details... how fast you want the current to rise, how fast it must fall, the interval between successive energize commands, when (and how) you plan to "reverse polarity" and for what purpose.

    Please tell us what you are trying to DO.

    Is this for some sort of ballistic accelerator, i.e., "rail gun" application? Or maybe a magnetic "levitation" application? Perhaps you are running a jail and need some way to sequence the locks on the inmate cells...
     
    Harald Kapp likes this.
  6. Blu35tarsix

    Blu35tarsix

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    Jan 26, 2017
    I am working on a new design for an electric motor. The magnets will need to fire on for a 4 count, off for 1 then reverse and repeat the pattern. 18 magnets will complete one revolution. So I would like to be able to possible control the count measure on the fly to increase or decrease speed. Thanks for the replies so far I appreciate it.
     
  7. Blu35tarsix

    Blu35tarsix

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    Jan 26, 2017
    Sorry I misspoke. On for 4 off for 1 reverse for 4 and then off for 9 and then repeat.
     
  8. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Unless the motor armature (the part that rotates and interacts with the electromagnets) turns very slowly, you need a fast-switching H-bridge for each electromagnet. And some means to control the back-emf that results when the current is switched off or reverses direction.

    You will probably need some feedback of the armature's angular position to determine when to "fire" each electromagnet and to control the rotation speed. A microprocessor is indicated to perform the timing, but discrete combinatorial logic is also possible. Do some due diligence to find out what others have done in this field to avoid duplicating the mistakes of others and re-inventing wheels that have long ago been perfected. There is hardly anything new under the sun when it comes to motors.

    Are you planning to use permanent magnets on the armature to react with the magnetic field produced by the electromagnets? Or is this a variable reluctance design? Variable reluctance motors show great promise in terms of efficiency and simplicity, but at the expense of greater complexity in switching the magnetic field.

    I was briefly involved with them in the 1990s as part of the U.S. Air Force More Electric Aircraft (MOE) initiative. They may be ready for prime time by now, but I've not kept up with the technology. Seemed to me at the time that they needed a compact nuclear reactor to power up the aircraft. That wasn't going to happen because President John F. Kennedy canceled the Aircraft Nuclear Propulsion Program in 1961,,, for political reasons, not because there had been no progress made. So good luck with your new motor.
     
  9. BobK

    BobK

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    Jan 5, 2010
    You can do the same thing with only 2 coils. In fact, it is in common usage and is called a stepper motor.

    Bob
     
  10. Blu35tarsix

    Blu35tarsix

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    Jan 26, 2017
    I will be using permanent magnets on the armature. Hevans1944 I appreciate your candor about diligence. I am definitely trying to do that. No sense in wasting time (yours or mine) and money. On a side note when creating an electromagnet and you are choosing a core, obviously different materials create a better magnet, but when a list shows relative permeability and it shows something 1000x more than another material will the more permeable material also be using more current to create that power? Or is it not an exact trade off? I hope you get what I'm asking.
     
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