bookbinding project - how can I do this please?

Discussion in 'The Projects Forum' started by pangolins, Dec 9, 2008.

  1. pangolins

    Thread Starter New Member

    Dec 9, 2008
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    Hello, firstly, what a great resource.

    I am a technical pigmy and am in need of help. I would like to construct a circuit that will magnetise a piece of metal and then cease to magnetise it, rhythmically.

    The circuit needs to be small, something I can embed into a cover. The whole thing will be 'docked' and I'm thinking that there would be a contact at the base of the cover which would meet another contact in the 'dock' which would be plugged into a wall plug or perhaps could run off a battery.

    I'm sure this can be done, but I don't have the first idea how, what components I would need, how I would put them together.

    I need to have a magnetic field that comes on and goes off regularly.

    I would be so very grateful for advice, this is for a competition and I have a deadline. If you are kind enough to leave me advice, could you take on board that this is the first time I will have done anything like this. If you could tell me what components I need to buy and what sort of shop I could find the items in, that would be extremely useful.

    Many thanks,
    the pangolin
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    About the only thing that would work is an electromagnet. That can be done by winding wire around a iron or mild steel core and passing current through the wire.

    Do you have any idea about the strength of the magnet? What happens as it goes on and off?

    Here is a link into our Ebook on electromagnetism - http://www.allaboutcircuits.com/vol_1/chpt_14/2.html
     
    Last edited: Dec 9, 2008
  3. pangolins

    Thread Starter New Member

    Dec 9, 2008
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    Thank you for replying so quickly. I didn't want to make my post too long.

    Its a book binding competition which has 'innovative function' as one of the parametres - hmmmmm.

    I want to have the sections of the book sewn onto thin iron/magnetically attracting metal. There are eight such rods - or will be. The first and last are stitched to the spine of the cover. The sections will not, as is classically the case, be attached to each other.

    In the cover on one side will be a circuit - of some sort, (panic). There will be a piece of metal embedded in the other cover which is potentially magnetic.

    The whole thing will be presented vertically, standing on its bottom edge. It will be supported by what I can only describe as a dock. This will be designed to support the base slightly, also designed to let the book start to fall apart, but in a controlled way.

    The magnetic field, when on, will hold the whole thing together. When off, the 'base unit' will prompt the book to begin to fall apart. Once it gets to a certain point - could i say 'turning moment' in this context??? - the current will come on, the metal in one cover then becoming a magnet, attracting the piece in the opposite cover, and the whole thing snap together.

    This is repeated, with an automated cutting off of the electricity - some kind of interrupter.

    The scope of movement can be very slight. As long as there is a slight pulsation. Even of a few millimetres.

    I hope you can follow, it is something that is, of course, easier to explain if I could show you with a diagram or bits of book.

    But basically, a way of turning a piece of metal into a magnet and then not, intermittently. With the circuit being small, small enough to fit into a space of a couple of millimetres, half a centimetre max........ gulp

    Any ideas? Thanks v much for even reading this far!

    Oh - the e-book/paper on the subject you were kind enough to link me to is really helpful. But I'd be very grateful for an idea of how I can connect to an electricity supply via a 'connection' of some sort in the 'dock' and also, how I can then get the electricity supply to come on and off to get the pulse I need... sorry to be so demanding.
     
    Last edited: Dec 9, 2008
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    The problem may be in trying to keep the magnetic element in the spine of the cover. Unless it can be quite bulky, the electromagnet would be more realistically housed in the dock.

    But that is getting ahead of the main problem, which is how much attraction is enough? When fixed in place, the magnetic field needed to hold the booked (is this correct?) pages with the associated metal rod will be relatively small.

    But magnetic fields lose attractiveness by the inverse square law, which means it will take significantly more attraction to pull the booked sections back in place after they have moved even a short distance. The weight of the paper will act as a lever that will try to pry the sections out of the influence of the field.

    To see a bit of this, get two magnets and try to press them together when the poles are in opposition. The last bit is very difficult. Pulling them apart is awkward, as the force need to start the separation is so much greater than that necessary after even a tiny bit of distance has been gained.

    You might get a metal rod (mild steel) and see what I mean. Place a mass of paper to the rod and have a magnet hold it upright. Move the rod away in the direction of the paper, and see how far you can go before the rod will not come back to the magnet when released.

    Controlling current in a coil is the very least of the problems here. And recall that junkyards move tons of material with electromagnets.
     
  5. pangolins

    Thread Starter New Member

    Dec 9, 2008
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    Thanks, yes the sections of the book will fall open, and it is the reactivation of the electrical coil that, I'm hoping, will cause the magnetic field activate, in turn. This then causes - I truly hope! - the two covers to snap back together.

    The 'dock' for want of a better word, has a base which is slightly (+/-) convex so that the sections 'want' to give into gravity and fall apart. The current comes back on, the magnet activates, the covers come together.

    I have spent some time familiarising myself with your very useful work sheets and info documents and feel clearer. I went to a hardware shop which helped a little but obviously I need an specialist electrical suppliers.

    The coil can't go into the dock because, when the magnetic field is activated, the book will just be hugged to one side of the dock, at an angle, and then, when de activated, the sections will not be able to fall apart because the whole thing will be leaning to one side.

    Sooooo, what i learned today was that the wire must be insulated, which is a drag because that will add to the thickness. problem number one. however, the guy did suggest that if I embed a thin 'plate' of metal - non permanent magnet - in one cover, I could embed several coils in the other, rather than one, thereby getting the same 'pull' divided between four coils and so making them smaller.

    It is important (in as much as any of this is important!!) to remember that the sections of the book are not attached to each other, there is no spine. Just eight separate, sets of pages. So they can open/fall apart, and then close/snap shut.

    The whole other issue is that the circuit needs to be able to come on and off more or less every second..... the end result needs to be that the book falls open slightly and then snaps shut, regularly and frequently. It's fine if the distance the sections start to seperate, is not great. I understand that to pull the two covers back would take a strong field, so that I need to accept only a slight movement if I am to avoid a huge coil. Its off-setting one against the other - thickness of coil vs distance the sections can be allowed to fall.

    Do i have to worry about heat please?

    Also, how can I interrupt the electricity supply so frequently, is a timer at the plug in to the wall a possibility. Can timers be set to come on and go off every second?

    Finally - and thanks, very much, for your time and thought, the connection. The 'book' needs to be able to come out of its base/'dock'. So how would I construct the 'contact'? Would it be a piece of the copper wire running, uninsulated, along the base of the cover with the circuit meeting a bare piece of metal in the base? And would that be dangerous? If I connected the base to a battery, would I get enough power flowing throught the circuit and be safe?

    I have to submit this in the middle of February and I am starting to worry. I am sure this can be done and I have three weeks off over Christmas, but I feel so lost as to how to proceed.

    Very many thanks again, for any pointers you can give. If the covers are thicker than one would normally think, that is fine since the parametres for the competition dictate something out of the ordinary - innovative function. so then they can just deal with the thick covers that come with innovative function. I can't be everywhere at once, as it were : )

    pangolins
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    One thing that comes to mind is that you might look into "magnet wire" for the coil. The insulation is a coat of enamel paint, which allows tighter winding than ordinary plastic insulation.

    Using a transformer to isolate the project from the mains is highly recommended. Safety has to be an important consideration.

    I keep having thoughts of a device known as a solenoid. That is a coil of wire wound around a hollow former. It also has an armature, generally a metal cylinder that is drawn into the hollow when current passes the coil. Without some feel for the force required, it is very hard to make a sensible suggestion as to one that might be suitable.

    Here is a link to one of hundreds of manufacturers - http://www.solenoidcity.com/solenoid/openframe/openframecatalog.htm - so you can see what I mean.

    Using a solenoid makes it possible to think of having several in the base of the dock. By means of monofilament line running over a rod, they could pull straight down, but pull the binding rods horizontally. That puts stabinizing weight in the dock and insures all electrical connections are out of reach.

    Just an variation on your idea.
     
  7. pangolins

    Thread Starter New Member

    Dec 9, 2008
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    Magnet wire, thank you I'll see if i can find out where to buy some.

    A transformer is a a good idea, but I'm not sure how I would connect it. Nor, I'm sorry to say, what the transformer would do, what it would 'transform'. Sorry, very ignorant there. I know it is the box that I have, for example, between this laptop and the wall socket. But I have never really understood what purpose it serves.

    I run the wire in repeated coils around the metal I'm intending to magnetise. I take the two ends and form a circuit which connects, some how to an electrical supply. How they connect is something I'm still not at all clear on.

    The connection needs to allow the 'book' to be removed from the 'dock' so I'm thinking a wire that touches another in the dock, to provide a contact point. But obviously I don't want anything exposed that could be dangerous. So then I wonder if I need the full electric current or if a battery would provide the power I would need without making the exposed area of wire in the dock, dangerous.

    In other words, I'm not sure how to 'plug' the whole thing in. Wall plug with timer - if timer can be set to cut off and then turn on each second. Problem one. Current up to dock in which there is a point of connection Problem two, which meets the base of the circuit in the cover (if that is where it ends up being). Problem three. Construction of circuit and coil around metal, Problem four.

    Thanks for solenoid reference. I'll follow your link, but I'm not at all clear how the solenoid would cause the top part of the cover, furthest away from the dock, snap together.

    I would be happy to put the mechanism in the base since when the book is removed from the dock, there is no need for magnetism - so the circuit is redundant. I only need the circuit when the sections are 'docked'. But I can't conceptualise your suggestion. lack of knowledge. sorry.

    Thanks for exploring this with me and I do feel you see what I'm getting at, which is a relief as it is hard to explain without being able to draw diagrams.

    Could you tell me if you know how I could have the current interrupted frequently and regularly,
    where I could find out about how to connect transformers and what a transformer does,
    and how I could construct a connection beween the source of electricity in the dock, to the circuit and its coil, in the cover, bearing in mind the book must be detachable.

    I cant plug the cover, with the circuit, in at the dock, because it must be possible for the cover to start to fall away when the magnetic field is off and if it is anchored at its base, it can not fall open.......hmmmmmmmm

    Pls don't give up on me! I know it sounds complicated, but it should be 'dooable' no? and if I cold just get the sections opening and closing at the top, however slightly, then I'd have a really good metaphore for the book itself. It wold be a compelling entry for the competition.

    You mention the force required. The text block is about a centimetre thick, so that is, in essence solid wood. If it is allowed to come apart and fall, then the scope of movement can be, say, three millimetres each side, six in all. So the magnets would need to attract over an empty space of six millimetres and a block of paper around one centimetre thick. Does that sound like it would need a very strong field? The movement can be slight, in a way it is all to the good if people have to look twice to see what has attracted their attention, namely that there is a slight pulsation.

    Pangolins
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    At another suggestion - you could perhaps use balsa wood? Keep the mass down and that lets you use a smaller electromagnet.

    The transformer isolates you from mains voltage, which is always going to be lethal if come in contact with. I don't know what resource you have at hand, so it is hard to suggest a source for components. I use Mouser Electronics and Digi-Key on line.

    I have to deal with some things for a bit, so I will have to get back to you. You might look at our Ebook to learn a bit about transformers.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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    I knew there was something I was trying to recall. Take a look at this link - http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/elemag.html. Notice that the magnetic force is greatest where the lines of force concentrate. That means that the attraction is greatest at the end if the cylinder, and least along the side.

    You can wind a coil on a puck shaped pole piece to make the depth less, but for good attraction, the electromagnet will have to be oriented properly.
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    One thought.

    If you go to a toolshop you can buy very cheaply a gadget for magnetising and demagnetising screwdrivers. This device does not use a power source. You could have a look at one and see if you could adapt the principle.

    They are basically toroidal permanent ceramic magnets which you draw the shaft of the tool through to magnetise/demagnetise.
     
  11. DickCappels

    Moderator

    Aug 21, 2008
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    The gizmo in the tool shop is just a permanent magnet.
     
  12. pangolins

    Thread Starter New Member

    Dec 9, 2008
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    Thank you for thinking this over.

    Balsa wood is a good idea, but I'm hoping to embed the circuit in the cover itself, if necessary having a thicker pair of covers than one would normally, but hopefully not too thick.

    The magnet and circuit would be just covered over by thick watercolour paper, laminated over a hollowed out piece of board (dense card). Then come the pages themselves and the other cover with the non permanent magnet, a thin sheet, occupying most of the board's surfaced and sandwiched between water colour paper and the outside board. It is the text block of about 1 cm or slightly over, that is the barrier through which the field has to attract. That and the two watercolour paper linings.

    I'll have a look at any articles you have on transformers. I'm getting to know my way around the useful work sheets and background articles here and thanks to them, have a clearer idea and am better able to explain myself in the hardware shop. Not that it helped much this weekend, since they weren't specialist enough, but he gave me the names of two stores to try this Friday. I'm in Belgium, sooo.. but if anyone knows what components I need and where I can get them online that would be great.

    The man in the shop suggested four separate coils to create a field that could be strong enough to snap the book back together when the circuit is turned on, but making the whole thing less bulky.... so the point at which the magnetic force is strongest could be multiplied by four and if the non permanent magnet in the opposite cover is a thin plate that is slightly smaller than the cover itself, the alignment will automatically be ok. No?

    Will I need to factor in heat as an issue please? And any ideas on how to maintain a connection to the electricity supply while not actually anchoring the cover to the 'dock' since the covers need to be able to start falling away from each other? They need to be able to 'roll' apart, on their bottom edge. I hope you can see what I'm getting at....

    perhaps i could start making a shopping list?

    Thanks again.
    Pangolins
     
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