The idea of winding inductive guitar pickups by hand is almost unthinkable. It uses extremely thin wire and is a repetitive, laborious process that nevertheless requires a certain amount of precision. It’s a prime candidate for automation, and while [Davide Gironi] did exactly that, he wasn’t entirely satisfied with his earlier version. He now has a new CNC version that is more full-featured and uses an ATMega8 microcontroller.
[Davide Gironi]’s previous version took care of winding and counting the number of turns, but it was still an assisted manual system that relied on a human operator. The new upgrade includes a number of features necessary to more fully automate the process, such as a wire tensioner, a wire guide and traverse mechanism (made from parts salvaged from a broken scanner), and an automatic stop for when the correct number of turns has been reached.
All kinds of small but significant details are covered in the build, such as using plastic and felt for anything that handles the wire — the extremely fine wire is insulated with a very thin coating and care must be taken to not scratch it off. Also, there is the need to compute how far the traverse mechanism must move the wire guide in order to place the new wire next to the previously-laid turn (taking into account the winding speed, which may be changing), and doing this smoothly so that the system does not need to speed up and slow down for every layer of winding.
This system is still programmed by hand using buttons and an LCD, but [Davide Gironi] says that the next version will use the UART in order to allow communication with (and configuration by) computer – opening the door to easy handling of multiple winding patterns. You can see video of the current version in action, below.
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Whether you’re just getting into electronics or could use a refresher on some component or phenomenon, it’s hard to beat the training films made by the U.S. military. This 1965 overview of transformers and their operations is another great example of clear and concise instruction, this time by the Air Force.
It opens to a sweeping orchestral piece reminiscent of the I Love Lucy theme. A lone instructor introduces the idea of transformers, their principles, and their applications in what seems to be a single take. We learn that transformers can increase or reduce voltage, stepping it up or down through electromagnetic induction. He moves on to describe transformer action, whereby voltages are increased or decreased depending on the ratio of turns in the primary winding to that of the secondary winding.
He explains that transformer action does not change the energy involved. Whether the turns ratio is 1:2 or 1:10, power remains the same from the primary to the secondary winding. After touching briefly on the coefficient of coupling, he discusses four types of transformers: power, audio, RF, and autotransformers.
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When you need a toroid the easiest source is often to wind it yourself. The problem being that placing a few hundred windings around a ferrite ring is a real drag, especially if you have to make several of them. This cheat developed by [Jim W.] will save a lot of time. He cuts the ring in half for the winding and reassembles it afterward.
Here you can see that he has half of the core mounted in a drill chuck. To get to this point he scored the ferrite before clamping half in a vice and whacking the extruding half with a block of wood and a hammer. He hasn’t found a perfect solution for scoring the material (a utility knife or a triangular file both work but have drawbacks). Leave a comment if you’ve got any bright ideas.
Once the core is in two pieces he used some copper pipe with one end flattened and bent to the shape of the ring segment. With it hot glued in place he takes it for a spin (shown in the clip after the break). Once the windings are done a bit of super glue recombines the halves. This sort of thing is great for monitoring power use.
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[Craig Carmichael] has been hard at work on his electric hub motor for cars. Unlike typical electrical vehicles the plan is to bypass the transmission, differential, and everything else all together by connecting directly to the hub of the wheel. The goal of giving greater thrust and still allowing the use of a gas engine if need be.
There’s really too much detail for us to even begin to try to explain the entire project in a short recap, but [Craig] builds the entire motor (from magnets to coil windings) and wires his own controller (from schematic to finished PCB), all while documenting the process thoroughly for those wishing to make their own.