Rotating Magnetic Fields, Explained

If you made a motor out of a magnet, a wire coil, and some needles, you probably remember that motors and generators depend on a rotating magnetic field. Once you know how it works, the concept is pretty simple, but did you ever wonder who worked it all out to start with? Tesla figures into it, unsurprisingly. But what about Michael Dobrowolsky or Walter Bailey? Not common names to most people. [Learn Engineering] has a slick video covering the history and theory of rotating magnetic field machines, and you can watch it below.

Motors operated on direct current were not very practical at the time and caused a jerky motion. However, Tesla and another inventor named Ferraris realized that AC current could cause a rotating magnetic field without a moving commutator.

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Spin Me Right Round, Baby: Generator Building Experiments For Mere Mortals

How many of you plan to build a wind-powered generator in the next year? Okay, both of you can put your hands down. Even if you don’t want to wind your coils manually, learning about the principles in an electric generator might spark your interest. There is a lot of math to engineering a commercial model, but if we approach a simple version by looking at the components one at a time, it’s much easier to understand.

For this adventure, [K&J Magnetics] start by dissect a commercial generator. They picked a simple version that might serve a campsite well, so there is no transmission or blade angle apparatus to complicate things. It’s the parts you’d expect, a rotor and a stator, one with permanent magnets and the other with coils of wire.

The fun of this project is copying the components found in the commercial hardware and varying the windings and coil count to see how it affects performance. If you have ever wound magnet wire around a nail to make an electromagnet, you know it is tedious work so check out their 3D printed coil holder with an embedded magnet to trigger a winding count and a socket to fit on a sewing machine bobbin winder. If you are going to make a bunch of coils, this is going to save headaches and wrist tendons.

They use an iterative process to demonstrate the effect of multiple coils on a generator. The first test run uses just three coils but doesn’t generate much power at all, even when spun by an electric drill. Six windings do better, but a dozen finally does the trick, even when turning the generator by hand. We don’t know about their use of cheap silicone diodes though, that seems like unintentional hobbling, but we digress.

Making turbine blades doesn’t have to be a sore chore either, and PVC may be the ticket there, you may also consider the vertical axis wind turbine which is safer at patio level. Now, you folks building generators, remember to tip us off!

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Smiling Robot Moves Without Wires

What could be cuter than a little robot that scuttles around its playpen and smiles all day? For the 2018 Hackaday prize [bobricius] is sharing his 2D Actuator for Micro Magnetic Robot. The name is not so cute, but it boasts a bill of materials under ten USD, so it should be perfect for educational use, which is why it is being created.

The double-layer circuit board hides six poles. Three poles run vertically, and three of them run horizontally. Each pole is analogous to a winding in a stepper motor. As the poles turn on, the magnetic shuttle moves to the nearest active pole. When the perpendicular windings activate, it becomes possible to lock that shuttle in place. As the windings activate in sequence, it becomes possible to move left/right and forward/back. The second video demonstrates this perfectly.

[bobricius] found inspiration from a scarier source, but wants us to know this is his creation, not a patent infringement. We are not lawyers.

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How Energy Gets Where Its Needed

Even if you’re reading this on a piece of paper that was hand-delivered to you in the Siberian wilderness, somewhere someone had to use energy to run a printer and also had to somehow get all of this information from the energy-consuming information superhighway. While we rely on the electric grid for a lot of our daily energy needs like these, it’s often unclear exactly how the energy from nuclear fuel rods, fossil fuels, or wind and solar gets turned into electrons that somehow get into the things that need those electrons. We covered a little bit about the history of the electric grid and how it came to be in the first of this series of posts, but how exactly does energy get delivered to us over the grid? Continue reading “How Energy Gets Where Its Needed”

The Electrical Grid Demystified

Our society needs energy, and lots of it. If you’re reading this then the odds are astronomically good that you’re on a computer somewhere using energy, with the power cord plugged into the mysterious “black box” that is the electrical grid. The same is true if you’re reading this on a laptop or phone, which was charged from said black box even though it may not be connected at this moment. No matter where you are, you’re connected to some sort of energy source almost all the time. For almost every one of us, we have power lines leading up to our homes, which presumably connect to a power plant somewhere. This network of power lines, substations, even more power lines, and power plants is colloquially known as the electrical grid which we will be exploring in a series of articles.

While the electrical grid is a little over a century old, humanity has been using various energy sources since the agricultural revolution at least. While it started with animal fat for candles, wind for milling grain, and forests for building civilizations, it moved on to coal and steam during the industrial revolution and has ended up in a huge interconnected network of power lines connected to nuclear, natural gas, coal, solar, and wind sites around the world. Regardless of the energy source, though, there’s one reason that we settled on using electricity as the medium for transporting energy: it’s the easiest way we’ve found to move it from place to place.

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Meter All The Phases: Three Phase Energy Meter With OpenWrt

Keeping track your overall electricity usage is a good thing, and it’s even better if you know where all the kilowatt-hours are going. [Anurag Chugh’s] house has the three phases coming from the electrical distribution box tidily organized: One for the lighting and fans, one for household appliances, and one for the hot water supply. To monitor and analyze the electrical fingerprint of his house, [Anurag] installed a 3 phase energy meter and hooked it up to the internet.

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Arduino Controlled Dahlander Motor Switch


Dahlander Switch

[Jean-Noel] is fixing a broken Lurem woodworking machine. This machine uses a three-phase Dahlander motor, which has three operation modes: stop, half speed, and full speed. The motor uses a special mechanical switch to select the operating mode. Unfortunately, the mechanical bits inside the switch were broken, and the motor couldn’t be turned on.

To solve the problem without sourcing a new switch, [Jean-Noel] built his own Arduino based Dahlander switch. This consists of three relays that select the wiring configuration for each speed mode. There’s also a button to toggle settings, and two lamps to show what mode the motor is currently in.

The Arduino runs a finite-state machine (FSM), ensuring that the device transitions through the modes in the correct order. This is quite important, since the motor could be damaged if certain restrictions aren’t followed. The state machine graph was generated using Fizzim, a free tool that generates not only FSM graphs, but also Verilog and VHDL code for the machines.

The final product is housed in a DIN rail case, which allows it to be securely mounted along with the rest of the wiring. The detailed write-up on this project explains all the details of the motor, and the challenges of building this replacement switch.