An Open-Source, Free Circuit Simulator

July 30, 2023 by Bryan Cockfield 60 Comments

The original circuit simulation software, called the Simulation Program with Integrated Circuit Emphasis, or SPICE as it is more commonly known, was originally developed at the University of Califorina Berkeley in the 1970s with an open-source license. That’s the reason for the vast versions of SPICE available now decades after the original was released, not all of which are as open or free as we might like. Qucs is a GPL circuit simulator. And if you want the GUI option, you might want to try out QucsStudio, which uses Qucs under the hood, and is free to use, but binary-only.

(Editor’s note: the author was confused between the GPL open-source Qucs and the closed-source, binary-only QucsStudio. We’ve cleaned that up.)

QucsStudio supports a wide range of circuit components and models much in the same fashion as other more popular SPICE programs, including semiconductor devices, passive components, and digital logic gates. Qucs also utilizes SPICE-based simulation, which can model various types of circuit behavior, such as DC, AC, transient, and small-signal analysis.

Unfortunately there are only Windows versions available, and although some might have some success running it under WINE. There are plenty of other options for those of us running non-Windows operating systems though. Here’s a review of 30 of them.

Thanks to [Electroagenda] for the tip!

Al Williams Tells All In The Logic Simulation Hack Chat

March 4, 2022 by Tom Nardi 1 Comment

The list of requirements for hosting one of our weekly Hack Chats is pretty short: you’ve got to be knowledgeable, passionate, and above all else, willing to put those two quantities on display for a group of like-minded strangers. Beyond that, we’re not too picky. From industry insider to weekend hobbyist, high school dropout to double doctorate, if you’ve got something interesting to talk about, we’re ready to listen.

But in casting a such a wide net, we occasionally forget that we’ve got a considerable collection of potential hosts within our own worldwide roster of contributors. Among this cast of characters, few can boast the same incredible body of knowledge as Al Williams, who was able to pencil in some time this week to host the Logic Simulation Hack Chat.

Or at least, that was the idea. In reality the Chat covered a wide range of topics, and was peppered with fascinating anecdotes pulled from Al’s decades of experience in the field. Though to be fair, we expected no less. He was building hardware before many of us were born, and can take credit for designs that have been at the bottom of the ocean as well as launched into orbit. He’s been writing about it just as long too, with articles of his appearing in iconic print magazines such as Dr. Dobb’s Journal.

Al has seen and done so much that he still surprises us with the occasional nugget, and we’ve been working with him for years. It was only a week or two back that he started a story with “Back when I used to manage a gas pipeline…” in the middle of a conversation about utility metering.

Of course, that’s not to say some technical discussion didn’t sneak in there from time to time. Sure Al’s recollection of how they used to literally crawl over the schematics for the 68000 back at Motorola might stick out as a particular high point, but he also explains his personal preference for vendor-specific software tools over their more generic open source counterparts. He also draws comparisons between hardware description languages (HDLs) like Verilog and parametric CAD tools such as OpenSCAD in the way that they help model complex relationships in ways that can’t be easily done by more traditional means.

At one point the conversation lingers on the design and production of application-specific integrated circuits (ASICs), and how they compare to field-programmable gate arrays (FPGAs). Traditionally ASICs have been out of reach for the hobbyist, but with the recent collaboration between Google and SkyWater Technology to create an open source process design kit (PDK), they’re now within the capabilities of a dedicated individual. Matt Venn spoke on the topic during Remoticon 2021, and it’s good to see more folks in the community openly discussing the possibilities of custom silicon designed by hackers.

From there, things start really getting wild. From dreaming of virtual reality circuit simulators that let you fly amongst your creations like in Tron, to salivating over high-end technologies such as reflective memory, this Chat really runs the gamut. But then, that’s sort of why we hold them in the first place. Whether you actively participate or are just along for the ride, the Hack Chat gives everyone in the community a chance to gather around a virtual water cooler with fascinating characters that you won’t find anywhere else.

The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to Hackaday.io make sure you don’t miss out.

Rockin’ Out In LTSpice: Simulating Classic Guitar Pedals

October 29, 2020 by Adam Zeloof 9 Comments

Musicians have a fantastic language to describe signals. A sound can be fat, dark, crunchy, punchy — the list goes on. These aren’t very technical terms, but they get the job done. After all, it’s much easier to ask to guitarist for a crisper sound than to ask them to sharpen the edges of the waveform, while amplifying the high-frequency components and attenuating the low-frequency components. Of course, it’s fun to look at signals this way as well, especially when you can correlate shifts in sound quality to changes in the waveform and, ideally, the circuit that produces it.

To undergo such an investigation, [Nash Reilly] has been simulating guitar effects pedals in LTSpice. Able to find most of the schematics he needs online, [Nash] breaks down the function of each part of the circuit and builds a simulation of the entire system. His write-up clearly explains, and often demonstrates, what’s going on inside the box. On the surface, it’s an interesting tour of the inner workings of your favorite effects pedals. Beyond that, it’s an excellent survey of analog design that is well-worth the read for anybody interested in audio, electronics, or audio electronics.

For those interested in taking the physical route rather than the simulated one, we’ve taken a look at pedal design before. Anybody who wants to try their hand at creating simulations can grab a copy of LTSpice, or check out a package called LiveSpice, which lets you simulate circuits in realtime and use them to process live audio — pretty useful for prototyping guitar effects.

What Rhymes With Spice And Simulates Huge Circuits?

May 28, 2020 by Al Williams 9 Comments

Most of us have computers on our desk that would have been considered supercomputers not long ago. We always wonder how many of them get any actual workout other than decoding video. If you want to simulate circuits you may very well start chewing up significant CPU time, so you might consider Xyce, an open source high-performance analog circuit simulator from Sandia National Labs. As you’d expect from a giant government lab it is able to support large scale parallel computing, but will also work on common desktop systems. On Linux, it will do what they call “small-scale parallelism.” In addition, it can deal with simulations of things as diverse as neural networks and power grids.

The code is open source, but oddly you do have to register to download it. Xyce has been around for a bit, but version 7.0 just arrived in April. Many of the changes are to improve compatibility with other Spice programs, notably HSpice.

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Hackaday Links: September 15, 2019

September 15, 2019 by Dan Maloney 28 Comments

It’s probably one of the first lessons learned by new drivers: if you see a big, red fire truck parked by the side of the road, don’t run into it. Such a lesson appears not to have been in the Tesla Autopilot’s driver education curriculum, though – a Tesla Model S managed to ram into the rear of a fire truck parked at the scene of an accident on a southern California freeway. Crash analysis reveals that the Tesla was on Autopilot and following another vehicle; the driver of the lead vehicle noticed the obstruction and changed lanes. Apparently the Tesla reacted to that by speeding up, but failed to notice the stationary fire truck. One would think that the person driving the car would have stepped in to control the vehicle, but alas. Aside from beating up on Tesla, whose AutoPilot feature seems intent on keeping the market for batteries from junked vehicles fully stocked, this just points out how far engineers have to go before self-driving vehicles are as safe as even the worst human drivers.

The tech press is abuzz today with stories about potential union-busting at Kickstarter. Back in March, Kickstarter employees announced their intent to organize under the Office and Professional Employees International Union (OPEIU). On Thursday, two of the union organizers were fired. Clarissa Redwine, who recently hosted a Hack Chat, was one of those released; both she and Taylor Moore are protesting their terminations as an illegal attempt to intimidate Kickstarter employees and keep them from voting for the union. For their part, Kickstarter management says that both employees and two more were released as a result of documented performance issues during the normal review cycle, and that fourteen employees who are in favor of the union were given raises during this cycle, with three of them having been promoted. There will no doubt be plenty more news about this to come.

Would you pay $900 for a Nixie clock? We wouldn’t, but if you choose to buy into Millclock’s high-end timepiece, it may help soften the blow if you think about it being an investment in the future of Nixie tubes. You see, Millclock isn’t just putting together an overpriced clock that uses surplus Russian Nixies – they’re actually making brand new tubes. Techmoan recently reviewed the new clock and learned that the ZIN18 tubes are not coming from Czech Republic-based Dalibor Farný, but rather are being manufactured in-house. That’s exciting news for Nixie builders everywhere; while Dalibor’s tubes are high-quality products, it can’t hurt to have a little competition in the market. Nixies as a growth industry in 2019 – who’da thunk it?

We ran across an interesting project on Hackaday.io the other day, one that qualifies as a true hack. How much house can you afford? A simple question, but the answer can be very difficult to arrive at with the certainty needed to sign papers that put you on the hook for the next 30 years. Mike Ferarra and his son decided to answer this question – in a circuit simulator? As it turns out, circuit simulators are great at solving the kinds of non-linear simultaneous equations needed to factor in principle, interest, insurance, taxes, wages, and a host of other inflows and outflows. Current sources represent money in, current sinks money paid out. Whatever is left is what you can afford. Is this how Kirchoff bought his house?

And finally, is your parts inventory a bit of a mystery? Nikhil Dabas decided that rather than trying to remember what he had and risk duplicating orders, he’d build an application to do it for him. Called WhatDidIBuy, it does exactly what you’d think; it scrapes the order history pages of sites like Adafruit, Digi-Key, and Mouser and compiles a list of your orders as CSV files. It’s only semi-automated, leaving the login process to the user, but something like this could save a ton of time. And it’s modular, so adding support for new suppliers is a simple as writing a new scraper. Forgot what you ordered from McMaster, eBay, or even Amazon? Now there’s an app for that.

The Augmented Reality Breadboard Of The Future

May 27, 2019 by Tom Nardi 15 Comments

You’d be hard pressed to find a carpenter who didn’t own a hammer, or a painter that didn’t have a couple of brushes kicking around. Some tools are simply so fundamental to their respective craft that their ownership is essentially a given. The same could be said of the breadboard: if you’re working with electronics on the hobby or even professional level, you’ve certainly spent a decent amount of time poking components and wires into one of these quintessential prototyping tools.

There’s little danger that the breadboard will loose its relevance going forward, but if [Andrea Bianchi] and her team have anything to say about it, it might learn some impressive new tricks. Developed at the Korean Advanced Institute of Science and Technology, VirtualComponent uses augmented reality and some very clever electronics to transform the classic breadboard into a powerful mixed-reality tool for testing and simulating circuits. It’s not going to replace the $3 breadboard you’ve got hiding at the bottom of your tool bag, but one day it might be standard equipment in electronics classrooms.

The short version is that VirtualComponent is essentially a dynamic breadboard. Holes in the same row are still electrically linked like in the classic breadboard, but with two AD75019 cross-point switch arrays and an Arduino in the base, it has the ability to virtually “plug in” components at arbitrary locations as selected by the user. So rather than having to physically insert a resistor, the user can simply tell the software to connect a resistor between two selected holes and the cross-point array will do the rest.

What’s more, many of those components can be either simulated or at least augmented in software. For example, by using AD5241 digital potentiometers, VirtualComponent can adjust the value of the virtual resistor. To provide variable capacitance, a similar trick can be pulled off using an array of real capacitors and a ADG715 digital switch to connect them together; essentially automating what the classic “Decade Box” does. In the demonstration video after the break, this capability is extended all the way out to connecting a virtual function generator to the circuit.

The whole system is controlled by way of an Android tablet suspended over the breadboard. Using the tablet’s camera, the software provides an augmented reality view of both the physical and virtual components of the circuit. With a few taps the user can add or edit their virtual hardware and immediately see how it changes the behavior of the physical circuit on the bench.

People have been trying to improve the breadboard for years, but so far it seems like nothing has really stuck around. Given how complex VirtualComponent is, they’ll likely have an even harder time gaining traction. That said, we can’t help but be excited about the potential augmented reality has for hardware development.

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Emulate ICs In Python

September 26, 2017 by Al Williams 16 Comments

Most people who want to simulate logic ICs will use Verilog, VHDL, or System Verilog. Not [hsoft]. He wanted to use Python, and wrote a simple Python framework for doing just that. You can find the code on GitHub, and there is an ASCII video that won’t embed here at Hackaday, but which you can view at ASCIInema.

Below the break we have an example of “constructing” a circuit in Python using ICemu:

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