Pendulum

Electric swing - good present for a child, and if well assembled, you can develop the idea into, for example, an office souvenir.

The basis of the toy is a simple mounted circuit (although it is of course better to do it on a board), consisting of a transistor, a diode and a specially wound coil hidden in the bottom. The “seat” of the swing is a magnet, it is better to choose a neodymium one, there are plenty of them now, although a regular one will do just fine.

The coil is wound with double wire, each with a cross-section of approximately 0.25-0.3, about 1500 turns, i.e. 2 copper wires are taken in parallel and wound onto a coil. The diagram shows that the end of the first wire is connected to the beginning of the second. I chose the shape of the coil for logical reasons: oval, because a magnet passing over it will interact better along the length of the larger diagonal of the ellipse. I didn't use the core, so you can experiment with it. It is better to wind it carefully, turn to turn, but it is not necessary.

A direct conduction transistor, you can take MP39...42, any diode, a regular 1.5 volt battery. For convenience, it is better to make a switch.

I apologize for the makeshift assembly, but I did it in my school years out of sheer enthusiasm using a diagram from my father’s old notebook with diagrams, so it’s not really known where it came from, and I just wanted to see how it works as quickly as possible.

It starts up simply, turn on the device and push the magnet, after a couple of seconds you will notice how intensely the pendulum begins to oscillate. The system will work better if it can create resonance, i.e. equality of the operating frequencies of the circuit and the natural frequency of the pendulum, which is calculated by the formula. Here this is achieved by adjusting all the parameters of the pendulum. It is better to secure the connecting rod on 2 bearings, and not on 1, like mine.