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building a strong solenoid

Discussion in 'General Electronics Discussion' started by davidbenjamindix, Dec 31, 2010.

  1. davidbenjamindix

    davidbenjamindix

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    Feb 25, 2010
    i want to 'build' my own solenoid to control a drawer in my woodworking project. it is a walnut box with hidden drawers that contain homemade neodymium magnetic locks. one or more of the drawers i would like a homemade solenoid to control the drawer opening and closing. i have a 4 channel 12volt DC remote control system, and one of the channels i would like to operate the solenoid with. now the drawer will be small, and i plan on building it with some type of slide or bearing (so it slides easy), and the drawer probably won't eject from the box no more than 5 or 6 inches.

    i already have thin magnetic wire (i can't remember...there are 3 sizes), and have build a small solenoid before using a plastic pen tube and a nail for the core. my question is, what is the best material i should be using for the tube (where the wire coils around), including the thickness of the tube, and diameter of the tube. i also need to know the cheapest type of core that i should be using. im assuming the core is going to be pretty light so it travels in and out easily?

    i also have another concern about the coil direction. how many wraps do i need....1000? should i wrap only one direction, and work out some type of switch that can change the current direction? or should i wrap both directions, use an on switch to suck the core into the tube, and use a spring to return the core after the current is removed? i'll take any advice or criticism, because im still learning, and still very inexperienced with electricity. thanks for your time!
    David Dix
     
    Last edited: Dec 31, 2010
  2. davidbenjamindix

    davidbenjamindix

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    0
    Feb 25, 2010
    i was just told i should just buy one. so now my question is, (im going for low cost) what kind of 12v DC solenoid should i buy? i suppose i will need a 2 way, and probably push type (because the drawer is going to be pushed out of the box). also, should i go with continuous duty?
     
  3. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    I don't know about any push-pull solenoids, but an ordinary solenoid can be made into this by using a magnet as a core instead of the iron slug that is usually used.
    Most solenoids also deal with strokes of just 0.5-2 inches at the most but longer can be made. Long strokes are associated with weak forces and high power consumptions.
    The force is usually weak at the start of the movement and growing much higher nearing the end. The shape of the slug determines much of this behaviour.
    Controlling the speed of solenoids is also something usually not done. They're usually used in systems where instant high-speed response/movement is wanted.
    Brass or stainless steel is usually used as tube lining for low friction, self-lubricating reasons. It should be covered with some insulation before applying the windings.
    Direction control (with a magnet core) can be done with two windings but this is a waste of precious space (& force) so an electronic polarity switch is preferable.
    I'm not saying it can't be done at all in your case but I see many design challenges and side effects that must be countered. Are motor drives unapplicable here?
     
  4. davidbenjamindix

    davidbenjamindix

    21
    0
    Feb 25, 2010
    i was suggested to use a drive from a cd/dvd player. im willing to use the cheapest, most effective way to accomplish this goal. since this project im working on is quite large and time consuming, i need to start being more efficient. the lockbox will have multiple hidden locks and drawers, as well as some nice LED lighting.
     
  5. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    If you have room for a solenoid, then you probably have room for a small electric motor. I would pattern the drawer opener after the mechanism of a garage door opener - screw drive or chain drive. The linear gear drive on a CD tray is a possibility if the mechanical tolerances of the drawer will keep the gear teeth engaged.
     
  6. shrtrnd

    shrtrnd

    3,674
    453
    Jan 15, 2010
    Laplace is probably right.
    Solenoids have very small distance-travel actuators, and you want to open a drawer, so you'd have to
    have a lever to transfer the small actuator stroke, into a long-length distance for the drawer.
    The other thing to consider, is the drag of I assume, wood drawer on wood supports.
    It's not all that expensive to get ball-bearing roller-slides for the drawer, and it would
    cut-down greatly on the drag of the drawer opening and closing.
    It sounds like you want this to be a cheap project. But if you want to spend a little money,
    you can get good results. Since you're using 12V, consider looking around at some
    of the Recreational Vehicle accessories. I've seen some really interesting devices for
    those things. It might not be designed to open drawers, but I've seen some really
    nice devices for something that could be made to work your idea.
    Another expensive, (unless you salvage from a car junk yard), would be an assembly
    like an electric window opener. That kind of device is made to order for your project.
    Just some other ideas to consider.
     
  7. davidbenjamindix

    davidbenjamindix

    21
    0
    Feb 25, 2010
    thanks for the input, suggestions, and great ideas! these are things i haven't thought of. greatly appreciated.
     
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