A Microwave Erector Set

July 16, 2018 by Al Williams 17 Comments

RF design isn’t always easy, especially at higher frequencies. Despite improvements in simulation tools, there’s still no substitute for prototyping and trying out different things. That wasn’t so bad when that meant nailing some nails in a piece of wood and wiring up discrete components. But at today’s microwave frequencies and with today’s IC packaging that simply doesn’t work. Solving this problem is what drives a company called X-Microwave. They have a standard grid pattern PCB for a wide range of RF circuits and accessories to tie them all together. Probably the best way to get a feel for the system is to watch the simple video below. There’s also a free simulator tool worth taking note of that you’ll see in a bit.

Before you get too excited, we’ll warn you that while this stuff is cheap if you need it, it isn’t an impulse buy. The baseboards and probes (the connectors) run from $150 to $300. You can get kits, too, but a bare-bones two-port system is going to start at about $550, which is about $100 off the component parts and includes some extras. Then you need less expensive parts to make the boxes around things if you need them. Oh. Then you also need the PCBs which are not cheap, either. Their prices vary widely as you’d expect, but — for example — we saw amplifiers as low as $80 and as high as nearly $1000. So a complete system could get pretty pricey.

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Open-source Circuit Simulation

April 29, 2018 by Bryan Cockfield 31 Comments

For simple circuits, it’s easy enough to grab a breadboard and start putting it together. Breadboards make it easy to check your circuit for mistakes before soldering together a finished product. But if you have a more complicated circuit, or if you need to do response modeling or other math on your design before you start building, you’ll need circuit simulation software.

While it’s easy to get a trial version of something like OrCAD PSpice, this software doesn’t have all of the features available unless you’re willing to pony up some cash. Luckily, there’s a fully featured free and open source circuit simulation software called Qucs (Quite Universal Circuit Simulator), released under the GPL, that offers a decent alternative to other paid circuit simulators. Qucs runs its own software separate from SPICE since SPICE isn’t licensed for reuse.

Qucs has most of the components that you’ll need for professional-level circuit simulation as well as many different transistor models. For more details, the Qucs Wikipedia page lists all of the features available, as does the project’s FAQ page. If you’re new to the world of circuit simulation, we went over the basics of using SPICE in a recent Hack Chat.

Thanks to [Clovis] for the tip!

Circuit VR: The Dickson Charge Pump

April 6, 2018 by Al Williams 23 Comments

There was a time when taking a low DC voltage — say a single battery — and converting it to a higher voltage was painful. Now, however, cheap and easy-to-use DC to DC converters are readily available. For some small tasks, though, these can seem like overkill. For example, consider a case where you need to supply a higher voltage for a MOSFET gate that doesn’t draw much current. Perhaps you need that higher voltage to trigger a microcontroller’s programming mode and nothing else. The current draw is minimal, and a full-blown DC to DC converter is overkill. For cases like that, it is tempting to use some voltage multiplication scheme. There are many, but for this post, I’m going to take you inside a Dickson charge pump. This is Circuit VR because not only are we going to discuss the circuit, we’ll look at an LT Spice simulation you can try yourself.

The Dickson is interesting because it doesn’t require any AC conversion or transformers. Instead, it uses diodes or other switching elements to transfer charge between capacitors in stages. Each stage will effectively increase the voltage by the supply voltage — in theory. Reality isn’t so kind, though, as we’ll see.

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Friday Hack Chat: Simulating Analog

March 28, 2018 by Brian Benchoff 9 Comments

Simulation is a valuable tool for any hardware developer. Instead of building hardware for a long debugging session, you can emulate a microcontroller and blink your lights with some Javascript. Instead of working on a Bluetooth protocol for your fitness wearable, you can just whip up some Javascript and get it working that way. Once all your Javascript is in order, then you can finally move over to hardware. It saves development time, and it saves money.

But this is all digital. What do you do if you’re working on an analog system? Lucky for you, there’s a system built for analog and mixed-signal analysis, and it’s been around for decades. This week we’re talking all about PSpice, a simulator for analog analysis that will give you voltages and currents across every node in a schematic.

For this week’s Hack Chat, we’re going to be talking about PSpice with [Abha Jain] and [Alok Tripathi]. [Abha] has worked at Cadence for 19 years and has been part of the PSpice R&D team for the last decade. She’s an MTech in VLSI Design Tools and Technology and holds multiple EDA patents. [Alok] graduated in 1993 with a B. Tech in Electrical Engineering. He started working at the Department of Atomic Energy in 1993 as a power supply and control system designer for particle accelerators. Currently, he’s working with Cadence and is the Product Engineering Architect for PSpice and OrCAD.

For this Hack Chat, we’re going to be discussing the challenges of system-level simulation, improving reliability, yield, and productivity of circuit design, the issues of Spice simulation, and answer the question, ‘on an infinite grid of one Ohm resistors, what is the resistance between two nodes a knight’s move apart?’ You are, of course, encouraged to add your own questions to the Hack Chat. You can do that by leaving the questions as a comment on this Hack Chat’s event page.

Our Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This week it’s going down at an unusual time: 8 AM Pacific, Friday, March 30th Want to know what time this is happening in your neck of the woods? Have a countdown timer!

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

Amazing Mechanical Linkages And The Software To Design Them

January 26, 2018 by Elliot Williams 53 Comments

Most of us are more bits-and-bytes than nuts-and-bolts, but we have the deepest appreciation for the combination of the two. So, apparently, does [rectorsquid]. Check out the design and flow of his rolling ball sculpture (YouTube, embedded below) to see what we mean. See how the arms hesitate just a bit as the ball is transferred? See how the upper arm gently places it on the ramp with a slight downward gesture? See how it’s done with one motor? There’s no way [rectorsquid] designed this on paper, right?

Of course he didn’t (YouTube). Instead, he wrote a simulator that lets him try out various custom linkages in real time. It’s a Windows-only application (sigh), but it’s free to use, while the video guides (more YouTube) look very comprehensive and give you a quick tour of the tool. Of special note is that [rectorsquid]’s software allows for sliding linkages, which he makes very good use of in the rolling ball sculpture shown here.

We’ve actually secretly featured [rectorsquid]’s Linkage software before, in this writeup of some amazing cosplay animatronic wings that used the program for their design. But we really don’t want you to miss out if you’re doing mechanical design and need something like this, or just want to play around.

If you’d like to study up on your nuts and bolts, check out our primer on the ubiquitous four-bar linkage, or pore through Hackaday looking for other great linkage-powered examples, like this automatic hacksaw or a pantograph PCB probe for shaky hands.

Anyone know of an open-source linkage simulator that can also output STL files for 3D printing? Or in any format that could be easily transformed into OpenSCAD? Asking for a “friend”.

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Quantum Weirdness In Your Browser

January 24, 2018 by Al Williams 29 Comments

I’ll be brutally honest. When I set out to write this post, I was going to talk about IBM’s Q Experience — the website where you can run real code on some older IBM quantum computing hardware. I am going to get to that — I promise — but that’s going to have to wait for another time. It turns out that quantum computing is mindbending and — to make matters worse — there are a lot of oversimplifications floating around that make it even harder to understand than it ought to be. Because the IBM system matches up with real hardware, it is has a lot more limitations than a simulator — think of programming a microcontroller with on debugging versus using a software emulator. You can zoom into any level of detail with the emulator but with the bare micro you can toggle a line, use a scope, and hope things don’t go too far wrong.

So before we get to the real quantum hardware, I am going to show you a simulator written by [Craig Gidney]. He wrote it and promptly got a job with Google, who took over the project. Sort of. Even if you don’t like working in a browser, [Craig’s] simulator is easy enough, you don’t need an account, and a bookmark will save your work.

It isn’t the only available simulator, but as [Craig] immodestly (but correctly) points out, his simulator is much better than IBM’s. Starting with the simulator avoids tripping on the hardware limitations. For example, IBM’s devices are not fully connected, like a CPU where only some registers can get to other registers. In addition, real devices have to deal with noise and the quantum states not lasting very long. If your algorithm is too slow, your program will collapse and invalidate your results. These aren’t issues on a simulator. You can find a list of other simulators, but I’m focusing on Quirk.

What Quantum Computing Is

As I mentioned, there is a lot of misinformation about quantum computing (QC) floating around. I think part of it revolves around the word computing. If you are old enough to remember analog computers, QC is much more like that. You build “circuits” to create results. There’s also a lot of difficult math — mostly linear algebra — that I’m going to try to avoid as much as possible. However, if you can dig into the math, it is worth your time to do so. However, just like you can design a resonant circuit without solving differential equations about inductors, I think you can do QC without some of the bigger math by just using results. We’ll see how well that holds up in practice.

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Nematoduino: A Roundworm Neural Model On An Arduino

October 13, 2017 by Dan Maloney 13 Comments

When it comes to building a neural network to simulate complex behavior, Arduino isn’t exactly the first platform that springs to mind. But when your goal is to model the behavior of an organism with only a handful of neurons, the constraints presented by an Arduino start to make sense.

It may be the most important non-segmented worm you’ve never heard of, but Caenorhabditis elegans, mercifully abbreviated C. elegans, is an important model organism for neurobiology, having had its entire nervous system mapped in 2012. [Nathan Griffith] used this “connectome” to simulate a subset of the diminutive nematode’s behaviors, specifically movements toward attractants and away from obstacles. Riding atop a small robot chassis, the Arduino sends signals to the motors when the model determines it’s time to fire the virtual worm’s muscles. An ultrasonic sensor stands in for the “nose touch” neurons of the real worm, and when the model is not busy avoiding a touch, it’s actively seeking something to eat using the “chemotaxis” behavior. The model is up on GitHub and [Nathan] hopes it provides an approachable platform for would-be neuroroboticists.

This isn’t the first time someone has modeled the nematode’s connectome in silico, but kudos to [Nathan] for accomplishing it within the constraints an Arduino presents.

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