circuit

57 Articles

Schematic of a circuit

Hacking Flux Paths: The Surprising Magnetic Bypass

February 21, 2025 by 3 Comments

If you think shorting a transformer’s winding means big sparks and fried wires: think again. In this educational video, titled The Magnetic Bypass, [Sam Ben-Yaakov] flips this assumption. By cleverly tweaking a reluctance-based magnetic circuit, this hack channels flux in a way that breaks the usual rules. Using a simple free leg and a switched winding, the setup ensures that shorting the output doesn’t spike the current. For anyone who is obsessed with magnetic circuits or who just loves unexpected engineering quirks, this one is worth a closer look.

So, what’s going on under the hood? The trick lies in flux redistribution. In a typical transformer, shorting an auxiliary winding invites a surge of current. Here, most of the flux detours through a lower-reluctance path: the magnetic bypass. This reduces flux in the auxiliary leg, leaving voltage and current surprisingly low. [Sam]’s simulations in LTspice back it up: 10 V in yields a modest 6 mV out when shorted. It’s like telling flux where to go, but without complex electronics. It is a potential stepping stone for safer high-voltage applications, thanks to its inherent current-limiting nature.

The original video walks through the theory, circuit equivalences, and LTspice tests. Enjoy!

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MIT Demonstrates Fully 3D Printed, Active Electronic Components

February 19, 2025 by 26 Comments

One can 3D print with conductive filament, and therefore plausibly create passive components like resistors. But what about active components, which typically require semiconductors? Researchers at MIT demonstrate working concepts for a resettable fuse and logic gates, completely 3D printed and semiconductor-free.

Now just to be absolutely clear — these are still just proofs of concept. To say they are big and perform poorly compared to their semiconductor equivalents would be an understatement. But they do work, and they are 100% 3D printed active electronic components, using commercially-available filament.

How does one make a working resettable fuse and transistor out of such stuff? By harnessing thermal expansion, essentially.

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close up hands holding lighting pcb

Circuit Secrets: Exploring A $5 Emergency Light

December 28, 2024 by 2 Comments

Who would’ve thought a cheap AliExpress emergency light could be packed with such crafty design choices? Found for about $5, this unit uses simple components yet achieves surprisingly sophisticated behaviors. Its self-latching feature and decisive illumination shut-off are just the beginning. A detailed analysis by [BigCliveDotCom] reveals a smart circuit that defies its humble price.

The circuit operates via a capacitive dropper, a cost-effective way to power low-current devices. What stands out, though, is its self-latching behavior. During a power failure, transistors manage to keep the LEDs illuminated until the battery voltage drops below a precise threshold, avoiding the dreaded fade-to-black. Equally clever is the automatic shut-off when the voltage dips too low, sparing the battery from a full drain.

Modifications are possible, too. For regions with 220V+ mains, swapping the dropper capacitor with a 470nF one can reduce heat dissipation. Replacing the discharge resistor (220k) with a higher value improves longevity by running cooler. What remarkable reverse engineering marvels have you come across? Share it in the comments!  After all, it is fun to hack into consumer stuff. Even if it is just a software hack.

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Modeling A Guitar For Circuit Simulation

August 19, 2023 by 20 Comments

Guitar effects have come a long way from the jangly, unaltered sounds of the 1950s when rock and roll started picking up steam. Starting in large part with [Jimi Hendrix] in the 60s, the number of available effects available to guitarists snowballed in the following decades step-by-step with the burgeoning electronics industry. Now, there are tons of effects, from simple analog devices that would have been familiar to [Hendrix] to complex, far-reaching, digital effects available to anyone with a computer. Another thing available to modern guitarists is the ability to model these effects and guitars in circuit simulators, as [Iain] does.

[Ian] plays a Fender Stratocaster, but in order to build effects pedals and amplifiers for it with the exact desired sound, he needed a way to model its equivalent circuit. For a simple DC circuit, this isn’t too difficult since it just requires measuring the resistance, capacitance, and inductance of the overall circuit and can be done with something as simple as a multimeter. But for something with the wide frequency range of a guitar, a little bit more effort needs to go into creating an accurate model. [Iain] is using an Analog Discovery as a vector network analyzer to get all of the raw data he needs for the model before moving on to some in-depth calculations.

[Iain] takes us through all of the methods of figuring out the equivalent impedance of his guitar and its cabling using simple methods capable of being done largely by hand and more advanced techniques like finding numerical solutions. By analyzing the impedance of the pickup, tone and volume controls, and cable, this deep dive into the complexities of building an accurate equivalent circuit model for his guitar could be replicated by anyone else looking to build effects for their specific guitars. If you’re looking for a more digital solution, though, we’ve seen some impressive effects built using other tools unavailable to guitarists in days of yore, such as MIDI and the Raspberry Pi.

Opening Up ASIC Design

April 5, 2023 by 7 Comments

The odds are that if you’ve heard about application-specific integrated circuits (ASICs) at all, it’s in the context of cryptocurrency mining. For some currencies, the only way to efficiently mine them anymore is to build computers so single-purposed they can’t do anything else. But an ASIC is a handy tool to develop for plenty of embedded applications where efficiency is a key design goal. Building integrated circuits isn’t particularly straightforward or open, though, so you’ll need some tools to develop them such as OpenRAM.

Designing the working memory of a purpose-built computing system is a surprisingly complex task which OpenRAM seeks to demystify a bit. Built in Python, it can help a designer handle routing models, power modeling, timing, and plenty of other considerations when building static RAM modules within integrated circuits. Other tools for taking care of this step of IC design are proprietary, so this is one step on the way to a completely open toolchain that anyone can use to start building their own ASIC.

This tool is relatively new and while we mentioned it briefly in an article back in February, it’s worth taking a look at for anyone who needs more than something like an FPGA might offer and who also wants to use an open-source tool. Be sure to take a look at the project’s GitHub page for more detailed information as well. There are open-source toolchains if you plan on sticking with your FPGA of choice, though.

How To Restore A Musical Amiga

December 24, 2022 by 21 Comments

Despite the huge strides in computing power and functionality that have been achieved in the past few decades, there are still some things that older computers can do which are basically impossible on modern machines. This doesn’t just include the ability to use older hardware that’s now obsolete, either, although that is certainly a perk. In this two-part restoration of an Amiga 500, [Jeremy] shows us some of these features like the ability to directly modify the audio capabilities of this retro machine.

The restoration starts by fixing some damage and cleaning up the rest of the machine so it could be powered up for the first time in 30 years. Since it was in fairly good shape he then started on the fun part, which was working with this computer’s audio capabilities. It includes a number of amplifiers and filters in hardware that can be switched on or off, so he rebuilt these with new op-amps and added some new controls so that while he is using his MIDI software he can easily change how it sounds. He also restored the floppy disk drives and cleaned up the yellowing on the plastic parts to improve the overall appearance, as well as some other general improvements.

These old Amigas have a lot going for them, but since [Jeremy] is a musician he mostly focused on bringing back some of the musical functionality of his childhood computer, although he did build up a lot of extra features in this machine as well. These types of audio circuits are not something found in modern computers, though, so to get a similar sound without using original hardware you’ll need to build something like this NES audio processing unit programmed in Verilog.

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Motorcycle Regulator By Popular Demand

May 23, 2022 by 23 Comments

A few weeks ago we posted a build of an avid motorcycle enthusiast named [fvfilippetti] who created a voltage regulator essentially from the ground up. While this was a popular build, the regulator only works for a small subset of motorcycles. This had a large number of readers clamoring for a more common three-phase regulator as well. Normally we wouldn’t expect someone to drop everything they’re doing and start working on a brand new project based on the comments here, but that’s exactly what he’s done.

It’s important to note that the solutions he has developed are currently only in the simulation phase, but they show promise in SPICE models. There are actually two schematics available for those who would like to continue his open-source project. Compared to shunt-type regulators, these have some advantages. Besides being open-source, they do not load the engine when the battery is fully charged, which improves efficiency. The only downside is that they have have added complexity as they can’t open this circuit except under specific situations, which requires a specific type of switch.

All in all, this is an excellent step on the way to a true prototype and eventual replacement of the often lackluster regulators found on motorcycles from Aprilia to Zero. We hope to see it further developed for all of the motorcycle riders out there who have been sidelined by this seemingly simple part. And if you missed it the first time around, here is the working regulator for his Bajaj NS200.