As I developed a device for pumping cot


This article is about how I developed a device for pumping a cot with a pendulum mechanism.
If interested - welcome under the cut.

This story began three and a half years ago, when my wife and I were preparing for the birth of a son. In addition, I attended to the purchase of a cot and began to explore the market on this subject. It turned out that to date, the following types of cribs sold:
  • Just a bed, standing on his feet. Legs are usually equipped with wheels.
  • The crib-rocking chair with arched runners.
  • Cot pendulum swing mechanism. mechanism are longitudinal (cot, rocking along the long side, as on the title picture), transverse (cot, rocking along the short side) or universal. In the latter case, the same bed may be collected and so and so.

    Still there are a cradle - a small cradle, which is convenient to put next to each other, when you do something, and the baby is awake.

    There are beds, playpens, Chinese. There are bed-transformers, they attached to the end of the dresser and changing table, too, and there are options with a pendulum. And much more exotic there.

    But I was determined it was a traditional crib, standard sizes from birch or beech, with the pendulum swinging mechanism. Well, as "a man of progressive, advanced views", I immediately thought that the hands are not the same bed to download. Surely, I thought, long ago devised mechanisms swing, you just go to the store and buy.

    However, to my surprise, it was found that there was no ready device on sale there. But there are tips. For example, tied one end of a rope to the leg, and the other - to the bed and shaking his leg, swing bed. You can even while sitting at the computer. And you can tie a rope to the table CD-ROM, and write a program that will open and close a table with some frequency. And, you can use the drive wipers old "Lada". And not buzzing, place it in the next room, and the rope out of this room to spend in the nursery through the holes, pulleys and blocks. There are tips even more radical - not swing at all. Because, probably, it is harmful, and even here in Sparta, for example, children do not swing, and all all arranged.

    Also councils were several patents, but no devices on them is not made. There was one like a manufacturer, I would have bought, probably, if their device. But at that moment it was no longer possible - as I understand it, the production, if it was, they turned.

    So I came up with the idea to develop your own device for rocking the crib.

    I have reviewed all of the patents and other materials found on the Internet that could help me. Children also had to dismantle the Chinese electric swing, to see what's inside.

    Gradually formed the requirements for the device:
    • Quiet. This means - no motor, gears, reducers should not be. You can, of course, the city of soundproofing, but it is better initially to do without all this.
    • Remote control. And this, in turn, means the ability of a device to shake the bed from the rest.
    • Easy to install on a cot. As a consequence, the ability to install, if not all, then at least the majority of commercially available beds. on the design of the device, I said to myself a few highlights. Firstly, the unit swing should adjust to the natural frequency of the crib, pushing it in well-defined, the right time, just as a person standing on the ground, rocking swing. In addition, communication with the drive crib should not be hard to do, so that a swinging bed at any time you can stop the hand without sacrificing drive and hands. The crib should swing itself, but the drive will only compensate for the friction dissipates energy. This in turn will determine the low power consumption device.

      Remember, at one time were popular "desktop perpetual motion"? There is a support coil and a swinging part - the magnet. It is enough to swing the "engine" and he will swing as long as it does not sit battery.


      The principle of operation of the device is simple - a magnet, flying over the coil, induces in her EMF, which changes sign at a time when the magnet begins to move away from the coil. That's on the same principle, I decided to set up your device. An important point - as a sensor, I decided to use the same drive coil (not, for example, another coil, opto-coupler or hall sensor). In other words, the microcontroller (a structure is assembled, of course, on it) first "listens" EMF in the coil, and then when the time connects the same coil to the power source.

      Walking the path from idea to the finished device, I had to solve a lot of issues. As a microcontroller came ATtiny24. Neodymium magnet was selected in the form of a washer with a diameter of 15 mm and a thickness of 8 mm. Another story with a coil - its parameters have to choose carefully, using as a theory and a few coils of prior art c different sizes, wire diameter and number of turns. Also varied geometry and core materials. Of course, I wanted to make a magnetic system as much as possible closed, ideally a magnet to move with minimal gaps between the poles of the core. In this case it would be achieved maximum efficiency of the device (and therefore the minimum amount of copper in the winding). However, for the sake of simplicity, high efficiency design had to be sacrificed. One embodiment of the coil (not final) is shown in the photo.


      To swing mechanism can move from place crib was provided for a displacement of the coil relative to the magnet in the equilibrium position.

      Remote control was carried out by a panel of Chinese finished with four buttons (start, stop, more, less) and a receiver to it. Who uses this control:


      The program for the microcontroller was provided six swing speed (varies, in fact, the length of the impulse nudging). For the sixth speed algorithm is a bit more complicated - it uses a series of short pulses to check the polarity induced voltage in the pauses between them. This allows for maximum energy swing.

      During these three years, as new ideas of the program is improving. For example, it was tried (and still used) algorithm dynamically change the length of the pulses depending on the period of oscillation of the crib. Also, an algorithm was created for a smooth rise and fall smoothly in the current drive coil, which determines the total, absolute quiet device. Without this improvement the device at work still publish some sound like the ticking of a clock. There is also the idea of ​​a PI feedback in the amplitude of oscillation, but this has not yet solved the problem of the definition of this amplitude by using existing "sensor".

      As the housing unit was selected body ready Gainta, after some time, he got a beautiful picture, engraved with a laser.


      Power supply - ready, 12 V, 2 A.

      A few photos of the device:


      Non-standard fasteners are cut by laser cutting and powder painted.

      And the video:

      We enjoyed our device swing about a year, my wife was very pleased. And then the child refused rocked in a crib, and the device turned out to be irrelevant for us.

      And then it turned out that such devices may be sold. But that's another story.

      If you enjoyed this article, I can tell you:
      - About how I was getting a patent for utility model, and it was almost useless in a real case occurred violation of my patent rights;
      - How I started to mass-produce and sell devices swing, but has not yet made a fortune;
      - How the device has a new control panel with the screen from Nokia 1202 as well as additional functions.



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