Custom Christmas Light Controller Blocks Blinks

December 27, 2021 by 8 Comments

Finding that his recently purchased LED Christmas lights defaulted to an annoying blinking pattern that took a ridiculous seven button presses to disable each time they were powered up, [Matthew Millman] decided to build a new power supply that keeps things nice and simple. In his words, the goal was to enable “all lights on, no blinking or patterns of any sort”.

Connecting the existing power supply to his oscilloscope, [Matthew] found the stock “steady on” setting was a 72 VAC peak-to-peak square wave at about 500 Hz. To recreate this, he essentially needed to find a 36 VDC power supply and swap the polarity back and forth at the same frequency. In the end the closest thing he could find in the parts bin was a HP printer power supply that put out 30 volts, so the lights aren’t quite as bright as they were before, but at least they aren’t blinking.

To turn that into a pair of AC square waves, the power supply is connected to a common L298 H-Bridge module. You might expect a microcontroller to show up at this point, but [Matthew] went old school, and created his two alternating 500 Hz square waves with a 555 timer and a 74HC74D dual flip-flop.

Unfortunately, he didn’t have the time to get a custom PCB made before Santa’s big night. Though as he points out, since legitimate L298s are backordered well into next year anyway, having the board in hand wouldn’t have helped much. The end result is that the circuit has to live on a breadboard for the current holiday season, but hopefully around this time next year we’ll get a chance to see the final product.

Lisp In 436 Bytes

December 23, 2021 by 26 Comments

You would assume that any programming language available back in the 1960s would be small enough to easily implement on today’s computers. That’s not always true though, since old languages sometimes used multiple passes. But in some cases, you can implement what would have been a full language decades ago in a tiny footprint. A case in point is a pretty good implementation of Lisp — including garbage collection — in 436 bytes.

SectorLISP claims to be the tiniest real language, beaten only by toy languages that are not really very useful. If you want to, you can try it in your browser, but that version has better error messages and persistent bindings, so it hogs up a whole 509 bytes.

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Is Cloud Seeding Good, Bad, Or Ugly?

December 20, 2021 by 34 Comments

The Chinese Communist Party celebrated its centenary on the 1st of July, 2021. For such a celebration, clear skies and clean air would be ideal. For the capable nation-state, however, one needn’t hope against the whims of the weather. One can simply control it instead!

A recent paper released by Tsinghua University indicated that China had used cloud seeding in order to help create nicer conditions for its 100-year celebration. Weather modification techniques have been the source of some controversy, so let’s explore how they work and precisely what it was that China pulled off.

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Keynote Video: Elecia White Finds Treasure In The Memory Map

December 16, 2021 by 9 Comments

If you dig microcontrollers, and you like to dig into how they work, Elecia White wants to help you navigate their innermost secrets with the help of memory map files. In this refreshingly funny, but very deep keynote talk from the 2021 Hackaday Remoticon, Elecia guides us through one of the most intimidating artifacts of compilation — a file that lists where everything is being put in the microcontroller’s memory — and points out landmarks that help to make it more navigable.

And when you need to look into the map file, you probably really need to look into the map file. When your embedded widget mysteriously stops working, memory problems are some of the usual suspects. Maybe you ran out of RAM or flash storage space, maybe you have some odd hard fault and you want to know what part of the program is causing the trouble, or maybe you need to do some speed profiling to make it all run faster. In all of these cases, you get an absolute memory address. What lives there? Look it up in the memory map!

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Teardown: Verizon AC791L Jetpack 4G Mobile Hotspot

December 14, 2021 by 24 Comments

The saying “time and tide wait for no man” is usually used as a verbal kick in the pants, a reminder that sometimes an opportunity must be seized quickly before it passes by. But it can also be interpreted as a warning about the perpetual march of time and how it impacts the world around us. In that case, we would do well to add cellular technology to the list of proverbial things that wait for no one. Do you need 5G? No. Do you want it? Probably not. But it’s here, so be a good consumer and dump all your 4G hardware in the name of technical progress.

This line of logic may explain how the Verizon-branded Netgear AC791L 4G “Jetpack” hotspot you see here, despite being in perfect working order, found itself in the trash. The onset of 5G must have been particularly quick for the previous owner, since they didn’t even bother to wipe their configuration information from the device. In the name of journalistic integrity I won’t divulge the previous owner’s identity; but I will say that their endearing choice of WPA2 key, iluvphysics, makes for a nice fit with our publication.

A quick check of eBay shows these devices, and ones like it, are in ample supply. At the time of this writing, there were more than 1,500 auctions matching the search term “Verizon jetpack”, with most of them going for between $20 and $50 USD. We like cheap and easily obtainable gadgets that can be hacked, but is there anything inside one of these hotspots that we can actually use? Let’s find out.

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Keynote Video: Dr. Keith Thorne Explains The Extreme Engineering Of The LIGO Hardware

December 9, 2021 by 18 Comments

The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a huge installation measured in kilometers that is listening for wrinkles in space-time. Pulling this off is a true story of hardware and software hacking, and we were lucky to have Dr. Keith Thorne dive into those details with his newly published “Extreme Instruments for Extreme Astrophysics” keynote from the 2021 Hackaday Remoticon.

Gravity causes space-time to stretch — think back to the diagrams you’ve seen of a massive orb (a star or planet) sitting on a plane with grid lines drawn on it, the fabric of that plane being stretch downward from the mass of the orb. If you have two massive entities like black holes orbiting each other, they give off gravitational waves. When they collide and merge, they create a brief but very strong train of waves. Evidence of these events are what LIGO is looking for.

Laser Interferometer diagramRai Weiss had the idea to look for gravitational waves using laser interferometers in about 1967, but the available laser technology was too new to accomplish the feat. In an interferometer, a laser is shot through a beam splitter and one beam reflects out and back over a distance, and is then recombined with the other half using a photodetector to measure the intensity of light. As the distance in the long leg changes, the relative phase of the lasers shift, and the power detected will vary.

LIGO is not your desktop interferometer. It uses a 5 kW laser input. The 4 km legs of the interferometer bounce the light back and forth 1,000 times for an effective 4,000 km travel distance. These legs are kept under extreme vacuum and the mirrors are held exceptionally still. It’s worth it; the instrument can measure at a precision of 1/10,000 the diameter of a proton!

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What’s The Deal With UEFI?

November 30, 2021 by 98 Comments

It seems like there are two camps, the small group of people who care about UEFI and everyone else who doesn’t really notice or care as long as their computer works. So let’s talk about what UEFI is, how it came to be, what it’s suitable for, and why you should (or shouldn’t) care.

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