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Showing posts from July, 2025

Challenge: Square a Voltage

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Your design task, should you decide to accept it: given an input voltage, square it. Ok, that’s too hard since squaring 8 volts would give you 64 volts, so let’s say the output should be 10% of the square, so 8 volts in would result in 6.4V. How do you do it? [Engineering Prof.] knows how and will show you what you can do in the video below. The circuit uses two op amps and some transistors. However, the transistors are used in a way that depends on the temperature, so it is important to use a transistor array so they are matched and will all be at the same temperature. The math depends on the fact that the transistor response has a natural log term in it, and the property that the sum of two logs is the same as the log of the product of the numbers. Because of the matching transistors, many of the terms in the equation cancel out. Because the transistors are current devices, the transistor circuit’s output current is the input current squared divided by the output transistor’s c...

A Crypto Miner Takes the Straight and Narrow

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As it stands, cryptocurrency largely seems to be a fad of the previous decade, at least as far as technology goes. During that time, many PC users couldn’t get reasonably priced graphics cards since most of them were going into these miners. In contrast, nowadays any shortages are because they’re being used to turn the Internet into an AI-fueled wasteland. But nonetheless, there is a lot of leftover mining hardware from the previous decade and unlike the modern AI tools getting crammed into everything we own, this dated hardware is actually still useful. [Zendrael] demonstrates this by turning an old mining rig into a media server . The mining rig is essentially nothing more than a motherboard with a large number of PCI slots, each designed for a GPU. PCI slots can do many other things, though, so [Zendrael] puts a terabyte solid state drive in each but one of the PCI cards using NVMe to PCI adapters. The final slot still hosts a GPU since the computer is being converted to a media s...

There Are Better Lego-Compatible Universal Joints Out There

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Lego’s Technic line features all kinds of mechanical devices, from cogs to gears to chains and even pneumatic components. However, the vast majority of these components are made out of plastic and are only capable of toy-like levels of performance. In the competitive world of Lego YouTube, builders often push these parts to their limits, breaking them more often than you might think. To that end, [Brick Experiment Channel] has been investigating stouter Lego-compatible universal joints from a variety of third-party manufacturers. The video starts with a simple demonstration, showing that a Lego universal joint pops apart at just 0.4 Nm of torque. It’s no surprise, given it relies on tiny plastic pins in snap-fit joints. However, this means that it’s not that hard to build a stronger universal joint to outperform the stock parts. The video steps through a range of other options available on the market. For example, CaDA builds a universal joint using aluminium sleeves, a copper cente...

Are Service Loops a Good Idea?

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Well, here’s an interesting idea: the service loop . Ever heard of it? We haven’t! In the video, the presenter explains the service loop serves two purposes: on the one hand it may provide strain relief, but chiefly these loops are installed so there will be extra available slack in the cable if you need to rewire it some day to change the configuration of your pinout. One major problem with the service loop may be that the single turn is enough to create an inductor which will then induce noise and cross-talk all over the place. Our rule of thumb is always to completely unroll wires and cables before using them. Do you have a theory about the benefits or problems with service loops? If you do, we’d love to hear what you think in the comments! If you’re interested in strain relief, we’ve covered that before, and you don’t need a service loop to do it! Check out Cheap Strain Relief By Casting Hot Glue In A 3D Print and Arduino Uno Strain Relief .   Thanks to [Oliver] for wr...