Intuition About Signals And Systems

Signals and systems theory is a tough topic. Terms like convolution and impulse response can be hard to understand on a visceral level and most books that talk about these things emphasize math over intuition. [Discretised] has a YouTube channel that already has several videos that promise to tackle these topics with “minimum maths, maximum intuition.” We particularly noticed the talks on convolution and impulse response.

We think that often math and intuition don’t always come together. It is one thing, for example, to know that E=I times R, and power is I times E, but it is another to realize that a half-watt transmitter delivers 5V into a 50Ω load and that one watt will take just over 7V into that same load.

The example used is computing how much smoke you can expect to create by setting off fireworks. We presume the math models are notional since we imagine a real model would be pretty complex and involve things like wind data. But it still makes a nice example.

If you don’t know anything about the topic, these might not be the right ones to try to learn the basics. But we do applaud people sharing their intuition on these complex subjects.

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Hacker Driven To Build R/C Forza Controller

Generic video game console controllers have certainly gotten better and more ergonomic since the hard corners of the Atari joystick. As beautiful and engrossing as games have become, the controller is still the least engaging aspect. Why race your sweet fleet of whips with an ordinary controller when you could pretend they’re all R/C cars?

[Dave] found an affordable 4-channel R/C controller in the Bezos Barn and did just that. It took some modifications to make it work, like making a daughter board to turn the thumb grip input from a toggle button to a momentary and figuring out what to do with the three-way slider switch, but it looks like a blast to use.

The controller comes in a 6-channel version with two pots on the top. Both versions have the same enclosure and PCB, so [Dave] already had the placement molded out for him when he decided to install a pair of momentary buttons up there. These change roles based on the three-way slider position, which switches between race mode, menu mode, and extras mode.

We love the way [Dave] turned the original receiver into a USB dongle that emulates an Xbox 360 controller — he made a DIY Arduino Pro Micro with a male USB-A, stripped down the receiver board, and wired them together. There’s an entire separate blog post about that, and everything else you’d need to make your own R/C controller is on GitHub. Check out the demo and overview of the controls after the break.

[Dave] is no stranger to making game controllers — we featured his DJ Hero controller modified to play Spin Rhythm XD a few months ago.

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Staged Train Wrecks: An Idea That Ran Out Of Steam

Before there were demolition derbies, there were train totalings. That’s right, somebody had the idea to take a couple of worn-out train engines that were ready for the scrap heap, point them at each other, and drive them full steam ahead. And their boss said capital idea, let’s do it. This was the late 1890s.

Maybe it wasn’t the safest way to spend an evening, but a staged train wreck was surely an awesome spectacle to behold. Imagine being one of the brave engineers who had no choice but to get the train going as fast as possible and then jump out at the last second. A demolition derby seems like child’s play by comparison.

The largest and most widely-publicized wreck was put on by a man named William George Crush who was trying to find new ways to promote the Missouri-Kansas-Texas passenger railway. Once he got the okay, Crush found a large field surrounded by three hills that made for excellent viewing. He stood up a temporary town complete with a circus tent restaurant, a wooden jail cell, and 200 rent-a-constables.

On September 15th, 1896, forty thousand people gathered to watch two trains collide along a section of purpose-built track. They hit each other going 50 mph (80 km/h) and both engines exploded, sending hot iron projectiles every which way. Several people were injured, a few died, and a hired photographer lost an eye to shrapnel. Train totalings nevertheless continued until the Great Depression of the 1930s, when the practice was discarded as wasteful.

Thanks for the tip, [Martin]!

An Analog IC Design Book Draft

[Jean-Francois Debroux] spent 35 years designing analog ASICs. He’s started a book and while it isn’t finished — indeed he says it may never be — the 180 pages he posted on LinkedIn are a pretty good read.

The 46 sections are well organized, although some are placeholders. There are sections on design flow and the technical aspects of design. Examples range from a square root circuit to a sigma-delta modulator, although some of them are not complete yet. There are also sections on math, physics, common electronics, materials, and tools.

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Pocket TV Now Shows The Inspection Channel 24/7

Those little pocket TVs were quite the cool gadget back in the ’80s and ’90s, but today they’re pretty much useless at least for their intended purpose of watching analog television. (If someone is out there making tiny digital-to-analog converter boxes for these things, please let us know.)

Now that analog pocket TVs are obsolete, they’re finally affordable enough for hacking into a useful tool like an inspection camera. [technichenews] found a nice Casio TV and a suitable analog pinhole camera that also does IR. Since the camera has RCA plugs and the TV’s video input is some long-gone proprietary 3.5mm cable, [technichenews] made a new video-only cable by soldering the yellow RCA wires up to the cable from an old pair of headphones. Power for the camera comes from a universal wall wart set to 12V.

Our favorite part of this project is the way that [technichenews] leveraged what is arguably the most useless part of the TV — the antenna — into the star. Their plan is to use the camera to peer into small engines, so by mounting it on the end of the antenna, it will become a telescoping, ball-jointed, all-seeing eye. You can inspect the build video after the break.

Need a faster, easier way to take a closer look without breaking the bank? We hear those slim earwax-inspection cameras are pretty good.

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RC HalfTrack Is Lasercut Masterpiece

The half-track is a vehicle design that has gradually fallen out of favour in the decades since World War II. Combining the benefits of easy driving and handling of wheeled vehicles with the strong mud and snow performance of a tracked vehicle, they served a niche before largely being phased out with the rise of the armoured personnel carrier. [JackCarter] wished to build his own, so whipped up a lasercut RC version of the SdKfz 251 22.

The work is impressive, with [JackCarter] creating the design in Solidworks from photos and illustrations of the vehicle. The moving parts are lasercut, including the tracks themselves, assembled from many tiny lasercut MDF parts. The benefit of using lasercutting to make the model is that it was easy for [Jack Carter] to create simple jigs to ease the process of putting the tracks together. A NodeMCU with a motor shield controls the gear motors used to drive the tracks, and drives a servo for steering. Control is via a smartphone, thanks to the Blynk framework which makes building apps for custom projects easy.

The finished product really shows off [JackCarter]’s 3D design skills, and looks like great fun to build and drive. We’d love to see it with a lick of paint and some period decals to really complete the look. Hackers love a good tracked vehicle, and we’ve seen some impressive builds before. Video after the break.

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A Tiny Jacob’s Ladder You Can Build At Home

Big fizzing electrical arcs are fun, and handled properly, not too dangerous either. The Jacob’s Ladder is one such piece of arc-generating equipment, one that featured heavily in vintage sci-fi films. It remains a charming demonstration of high-voltage electrical principles, and you can easily build your own mini version at home.

The build starts with a basic high-voltage step-up kit that turns 4V DC into 15 kV at the output. At this voltage level, it’s possible to generate an arc in air. To create the Jacob’s ladder, the kit is wired up to a pair of closely-spaced electrodes that slowly get farther apart as they go up vertically. When an arc jumps from one electrode to the other, it ionises the air, and the voltage sags due to the current flow. The flowing current heats up the air, which begins to rise, taking the current path with it, causing the familiar climbing arc we all know and love. As the distance between the electrodes increases towards the top, the arc can eventually no longer be sustained. With no current flowing, the voltage rises again, and a new arc forms at the bottom of the device, repeating the process.

It’s a fun build that would make an excellent desk toy, albeit best shown under glass to avoid accidental electric shocks. You can even build a larger one out of microwave parts if you’re so inclined. Video after the break.

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