Circuit Impedance Calculations Without Cumbersome Simulations

March 2, 2021 by Bryan Cockfield 11 Comments

Using circuit simulating software like SPICE can be a powerful tool for modeling the behavior of a circuit in the real world. On the other hand, it’s not always necessary to have all of the features of SPICE available all the time, and these programs tend to be quite expensive as well. To that end, [Wes Hileman] noticed an opportunity for a specific, quick method for performing impedance calculations using python without bulky, expensive software and came up with a program which he calls fastZ.

The software works on any network of passive components (resistors, capacitors, and inductors) and the user can specify parallel and series connections using special operators. Not only can the program calculate the combined impedance but it can perform frequency analysis at a specified frequency or graph the frequency response over a wide range of frequencies. It’s also running in python which makes it as simple as importing any other python package, and is also easy to implement in any other python program compared to building a simulation and hoping for the best.

If you find yourself regularly drawing Bode plots or trying to cobble together a circuit simulation to work with your python code, this sort of solution is a great way to save a lot of headache. It is possible to get the a piece of software like SPICE to to work together with other python programs though, often with some pretty interesting results.

Street-Legalize Your Ebike With A Magnet

March 1, 2021 by Bryan Cockfield 98 Comments

Getting into e-biking is a great hobby. It can get people on bikes who might otherwise not be physically able to ride, it can speed up commute times, and it can even make hauling lots of stuff possible and easy, not to mention it’s also fun and rewarding. That being said, there are a wide array of conflicting laws around what your e-bike can and can’t do on the road and if you don’t want to run afoul of the rules you may need a programmable device that ensures your e-bike is restricted in the appropriate way.

This build is specifically for Bafang mid drives, which can be up to 1000 W and easily power a bike beyond the speed limit where [Tomblarom] lives. A small microcontroller is housed in a waterproof box on the bike and wired between the motor’s display and controller. A small hall effect sensor and magnet sit by this microcontroller, and if the magnet is removed then the microcontroller reprograms the bike’s controller to limit the speed and also to disable the throttle, another feature that is illegal in some jurisdictions but not others. As an added bonus, the microcontroller also handles brake lights, turn signals, and automatic headlights for the bike as well.

While the project page mentions removing the magnet while getting pulled over to avoid fines and other punishments, that’s on you. We imagine this could still be useful for someone who wants to comply with local laws when riding on the road, but still wants to remove the restrictions when riding on private property or off-road where the wattage and speed restrictions might not apply.

Wind Turbines And Ice: How They’re Tailored For Specific Climates

March 1, 2021 by Bryan Cockfield 75 Comments

Wind turbines are incredible pieces of technology, able to harvest wind energy and deliver it to the power grid without carbon emissions. Their constant development since the first one came online in 1939 mean that the number of megawatts produced per turbine continues to rise as price per megawatt-hour of wind energy continues to fall. Additionally, they can operate in almost any climate to reliably generate energy almost anywhere in the world from Canada to the North Atlantic to parts beyond. While the cold snap that plowed through the American South recently might seem to contradict this fact, in reality the loss of wind power during this weather event is partially a result of tradeoffs made during the design of these specific wind farms (and, of course, the specifics of how Texas operates its power grid, but that’s outside the scope of this article) rather than a failure of the technology itself.

First, building wind turbines on the scale of megawatts isn’t a one-size-fits-all solution. Purchasing a large turbine from a company like GE, Siemens, or Vestas is a lot like buying a car. A make and model are selected first, and then options are selected for these base models. For example, low but consistent wind speeds demand a larger blade that will rotate at a lower speed whereas areas with higher average wind speeds may be able to get by with smaller and less expensive blades for the same amount of energy production. Another common option for turbines is cold weather packages, which include things like heaters for the control systems, hydraulics, and power electronics, additional insulation in certain areas, and de-icing solutions especially for the turbine blades.

In a location like Texas that rarely sees cold temperatures for very long, it’s understandable that the cold weather packages might be omitted to save money during construction (although some smaller heaters are often included in critical areas to reduce condensation or humidity) but also to save on maintenance as well: every part in a wind turbine has to be maintained. Continuing the car analogy, it’s comparable to someone purchasing a vehicle in a cold climate that didn’t come equipped with air conditioning to save money up front, but also to avoid repair costs when the air conditioning eventually breaks. However, there are other side effects beyond cost to be considered when installing equipment that’s designed to improve a turbine’s operation in cold weather.

Let’s dig into the specifics of how wind turbine equipment is selected for a given wind farm.

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Electroplating 3D Printed Parts For Great Strength

March 1, 2021 by Bryan Cockfield 33 Comments

Resin 3D printers have a significant advantage over filament printers in that they are able to print smaller parts with more fine detail. The main downside is that the resin parts aren’t typically as strong or durable as their filament counterparts. For this reason they’re often used more for small models than for working parts, but [Breaking Taps] wanted to try and improve on the strength of these builds buy adding metal to them through electroplating.

Both copper and nickel coatings are used for these test setups, each with different effects to the resin prints. The nickel adds a dramatic amount of stiffness and the copper seems to increase the amount of strain that the resin part can tolerate — although [Breaking Taps] discusses some issues with this result.

While the results of electroplating resin are encouraging, he notes that it is a cumbersome process. It’s a multi-step ordeal to paint the resin with a special paint which helps the metal to adhere, and then electroplate it. It’s also difficult to ensure an even coating of metal on more complex prints than on the simpler samples he uses in this video.

After everything is said and done, however, if a working part needs to be smaller than a filament printer can produce or needs finer detail, this is a pretty handy way of adding more strength or stiffness to these parts. There’s still some investigating to be done, though, as electroplated filament prints are difficult to test with his setup, but it does show promise. Perhaps one day we’ll be able to print with this amount of precision using metal directly rather than coating plastic with it.

Thanks to [smellsofbikes] for the tip!

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Reliable Frequency Reference From GPS

February 28, 2021 by Bryan Cockfield 35 Comments

GPS technology is a marvel of the modern world. Not only can we reliably locate positions on the planet with remarkable accuracy and relatively inexpensive hardware, but plenty of non-location-based features of the technology are available for other uses as well. GPS can be used for things like time servers, since the satellites require precise timing in order to triangulate a position, and as a result they can also be used for things like this incredibly accurate frequency reference.

This project is what’s known as a GPSDO, or GPS-disciplined oscillator. Typically they use a normal oscillator, like a crystal, and improve its accuracy by pairing it with the timing signal from a GPS satellite. This one is a standalone model built by [Szabolcs Szigeti] who based the build around an STM32 board. The goal of the project was purely educational, as GPSDOs of various types are widely available, but [Szabolcs] was able to build exactly what he wanted into this one including a custom power supply, simple standalone UI, and no distribution amplifier.

The build goes into a good bit of detail on the design and operation of the device, and all of the PCB schematics and source code are available on the projects GitHub page if you want to build your own. There are plenty of other projects out there that make use of GPS-based time for its high accuracy, too, like this one which ties a GPS time standard directly to a Raspberry Pi.

A Nerf Gun Upgrade

February 18, 2021 by Bryan Cockfield 16 Comments

A lot of us have nostalgia for our childhood toys, and as long as they’re not something like lawn darts that nostalgia often leads to fun upgrades since some of us are adults with industrial-sized air compressors. Classics like Super Soakers and Nerf guns are especially popular targets for improvements, and this Nerf machine gun from [Emiel] is no exception.

The build takes a Nerf ball-firing toy weapon and basically tosses it all out of the window in favor of a custom Nerf ball launching rifle. He starts with the lower receiver and machines a pneumatic mechanism that both loads a ball into the chamber and then launches it. This allows the rifle to be used in both single-shot mode and also in fully-automatic mode. From there, a barrel is fashioned along with the stock and other finishing touches.

[Emiel] also uses a high-speed camera to determine the speed of his new Nerf gun but unfortunately it isn’t high-speed enough, suffering from the same fate as one of the fastest man-made objects ever made, and he only has a lower bound on the speed at 400 km/h. If you don’t want to go fast with your Nerf builds, though, perhaps you should build something enormous instead. Continue reading “A Nerf Gun Upgrade” →

Steam Engine Replica From LEGO

January 25, 2021 by Bryan Cockfield 25 Comments

If engineering choices a hundred years ago had been only slightly different, we could have ended up in a world full of steam engines rather than internal combustion engines. For now, though, steam engines are limited to a few niche applications and, of course, models built by enthusiasts. This one for example is built entirely in LEGO as a scale replica of a steam engine originally produced in 1907.

The model is based on a 2500 horsepower triple-expansion four-cylinder engine that was actually in use during the first half of the 20th century. Since the model is built using nothing but LEGO (and a few rubber bands) it operates using a vacuum rather than with working steam, but the principle is essentially the same. It also includes Corliss valves, a technology from c.1850 that used rotating valves and improved steam engine efficiency dramatically for the time.

This build is an impressive recreation of the original machine, and can even run at extremely slow speeds thanks to a working valve on the top, allowing its operation to be viewed in detail. Maximum speed is about 80 rpm, very close to the original machine’s 68 rpm operational speed. If you’d prefer your steam engines to have real-world applications, though, make sure to check out this steam-powered lawnmower.

Thanks to [Hari] for the tip!

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