simulation

102 Articles

SMA Connector Footprint Design For Open Source RF Projects

June 2, 2023 by 10 Comments

When you first start out in the PCB layout game and know just enough to be dangerous, you simply plop down a connector, run a trace or two, and call it a hack. As you learn more about the finer points of inconveniencing electrons, dipping toes into the waters of higher performance, little details like via size, count, ground plane cutouts, and all that jazz start to matter, and it’s very easy to get yourself in quite a pickle trying to decide what is needed to just exceed the specifications (or worse, how to make it ‘the best.’) Connector terminations are one of those things that get overlooked until the MHz become GHz. Luckily for us, [Rob Ruark] is on hand to give us a leg-up on how to get decent performance from edge-launch SMA connections for RF applications. These principles should also hold up for high-speed digital connections, so it’s not just an analog game.

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Peering Down Into Talking Ant Hill

April 19, 2023 by 14 Comments

Watching an anthill brings an air of fascination. Thousands of ants are moving about and communicating with other ants as they work towards a goal as a collective whole. For us humans, we project a complex inner world for each of these tiny creatures to drive the narrative. But what if we could peer down into a miniature world and the ants spoke English? (PDF whitepaper)

Researchers at the University of Stanford and Google Research have released a paper about simulating human behavior using multiple Large Language Models (LMM). The simulation has a few dozen agents that can move across the small town, do errands, and communicate with each other. Each agent has a short description to help provide context to the LLM. In addition, they have memories of objects, other agents, and observations that they can retrieve, which allows them to create a plan for their day. The memory is a time-stamped text stream that the agent reflects on, deciding what is important. Additionally, the LLM can replan and figure out what it wants to do.

The question is, does the simulation seem life-like? One fascinating example is the paper’s authors created one agent (Isabella) intending to have a Valentine’s Day party. No other information is included. But several agents arrive at the character’s house later in the day to party. Isabella invited friends, and those agents asked some people.

A demo using recorded data from an earlier demo is web-accessible. However, it doesn’t showcase the powers that a user can exert on the world when running live. Thoughts and suggestions can be issued to an agent to steer their actions. However, you can pause the simulation to view the conversations between agents. Overall, it is incredible how life-like the simulation can be. The language of the conversation is quite formal, and running the simulation burns significant amounts of computing power. Perhaps there can be a subconscious where certain behaviors or observations can be coded in the agent instead of querying the LLM for every little thing (which sort of sounds like what people do).

There’s been an exciting trend of combining LLMs with a form of backing store, like combining Wolfram Alpha with chatGPT. Thanks [Abe] for sending this one in!

Blender And OpenEMS Teamed Up Make Stunning Simulations

April 1, 2023 by 5 Comments

There’s tons of theory out there to explain the behavior of electronic circuits and electromagnetic waves. When it comes to visualization though, most of us have had to make do with our lecturer’s very finest blackboard scribbles, or some diagrams in a textbook. [Sam A] has been working on some glorious animated simulations, however, which show us various phenomena in a far more intuitive way.

The animations were created in Blender, the popular 3D animation software. As for the underlying simulation going on behind the scenes, this was created using the openEMS platform. [Sam] has used openEMS to run electromagnetic simulations of simple circuits via KiCAD. From there, it was a matter of finding a way to export the simulation results in a way that could be imported into Blender. This was achieved with Paraview software acting as a conduit, paired with a custom Python script.

The result is that [Sam] can produce visually pleasing electromagnetic simulations that are easy to understand. One needn’t imagine a RF signal’s behaviour in a theoretical coax cable with no termination, when one can simply see what happens in [Sam]’s animation. 

Simulation is a powerful tool which is often key to engineering workflows, as we’ve seen before.

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IBIS Models Explained

March 26, 2023 by 2 Comments

If you’ve worked with circuit simulation, you may have run into IBIS models. The acronym is input/output buffer information, and while you can do a lot without having to deal with IBIS, knowing about it can help you have a successful simulation.

IBIS is an industry-standard format that uses ASCII text to describe voltage versus current and voltage versus time about some device’s digital input and output pins. This allows precise simulation without revealing the device’s internals, which is important to some vendors. The first post of this two-part series talks about what IBIS is and how it got started. The second part explains creating and using LTSpice to create your own IBIS models. It also covers why you might want to do that.

Of course, if you don’t care about revealing the internals of a device, you could just create a Spice simulation. However, many tools will accept both models, so it is useful to know how to produce either kind of model. In fact, to create an IBIS model, you’ll want to use a Spice model to generate the data for the IBIS model, so it is a good bet you’ll have both, even if you choose to only publish the IBIS models.

If you need a refresher on Spice, we have a series. If you prefer using something different, try Micro-Cap 12, which was commercial, but went free a few years ago.

Create Your RTL Simulations With KiCAD

February 6, 2023 by 4 Comments

[Bob Alexander] is in the process of designing a homebrew discrete TTL CPU, and wanted a way to enter schematics for digital simulations via a Verilog RTL flow. Since KiCAD is pretty good at handling hierarchical schematics, why not use that? [Bob] created a KiCAD plugin, KiCadVerilog allowing one to instantiate and wire up the circuits under consideration, and then throw the resulting Verilog file at your logic simulator of choice.

KiCadVerilog doesn’t do all the hard work though, as it only provides the structure and the wiring of the circuit. The actual guts of each TTL instance needs to be provided, and a reference to it is manually added to the schematic object fields. That’s a one-time deal, as you can re-use the component library once generated. Since TTL logic has been around for a little while, locating a suitable Verilog library for this is easy. Here’s ice-chips-verilog by [TimRudy] on GitHub for starters. It’s intended as a collection for Icestudio (which is also worth a look). Still, the Verilog code for many TTL series devices is presented ready for the taking, complete with individual test benches in case you need them.

Check out the project GitHub page for the module source code, and some more documentation about the design process.

We’ve seen many RTL hacks over the years, here’s an interesting way to generate a PCB layout with discrete logic, direct from the RTL.

Simulating Temperature In VR Apps With Trigeminal Nerve Stimulation

October 24, 2022 by 10 Comments

Virtual reality systems are getting better and better all the time, but they remain largely ocular and auditory devices, with perhaps a little haptic feedback added in for good measure. That still leaves 40% of the five canonical senses out of the mix, unless of course this trigeminal nerve-stimulating VR accessory catches on.

While you may be tempted to look at this as a simple “Smellovision”-style olfactory feedback, the work by [Jas Brooks], [Steven Nagels], and [Pedro Lopes] at the University of Chicago’s Human-Computer Integration Lab is intended to provide a simulation of different thermal regimes that a VR user might experience in a simulation. True, the addition to an off-the-shelf Vive headset does waft chemicals into the wearer’s nose using three microfluidics pumps with vibrating mesh atomizers, but it’s the choice of chemicals and their target that makes this work. The stimulants used are odorless, so instead of triggering the olfactory bulb in the nose, they target the trigeminal nerve, which also innervates the lining of the nose and causes more systemic sensations, like the generalized hot feeling of chili peppers and the cooling power of mint. The headset leverages these sensations to change the thermal regime in a simulation.

The video below shows the custom simulation developed for this experiment. In addition to capsaicin’s heat and eucalyptol’s cooling, the team added a third channel with 8-mercapto-p-menthan-3-one, an organic compound that’s intended to simulate the smoke from a generator that gets started in-game. The paper goes into great detail on the various receptors that can be stimulated and the different concoctions needed, and full build information is available in the GitHub repo. We’ll be watching this one with interest.

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Hack Your Engine Virtually

August 11, 2022 by 21 Comments

It is no secret that we like simulating circuits before we build something and there are plenty of great tools for that. But what about those of us who work on cars? Well, you might try engine-sim which is a real-time internal combustion engine simulation. Honestly, the program freely admits that it isn’t accurate enough to do engineering or engine tuning. But on the plus side, it has audio output and is at least good as an educational tool to show an engine running and how different parameters might affect it. You can see a video of the tool below.

[Ange-Yaghi] mentions that the code was primarily to power the YoutTube demo. However, the Readme hints that it might be better — or at least different — and collaboration to make it better is welcome.

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