Author: Al Williams

4506 Articles

Query Your C Code

April 8, 2024 by 17 Comments

If you’ve ever worked on a large project — your own or a group effort — you know it can be difficult to find exactly where you want to be in the source code. Sure, you can use ctags and most other editors have some way of searching for things. But ClangQL from [AmrDeveloper] lets you treat your code base like a database.

Honestly, we’ve often thought about writing something that parses C code and stuffs it into a SQL database. This tool leverages the CLang parser and lets you write queries like:

SELECT * FROM functions

That may not seem like the best example, but how about:

SELECT COUNT(name) FROM functions WHERE return_type="int"

That’s a bit more interesting. The functions table provides each function’s name, signature, a count of arguments, a return type, and a flag to indicate methods. We hope the system will grow to let you query on other things, too, like variables, templates, preprocessor defines, and data types. The tool can handle C or C++ and could probably work with other CLang front ends with a little work.

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Royal Typewriter Gets A Second (or Third) Life

April 8, 2024 by 13 Comments

Usually when we are restoring something with a keyboard, it is some kind of old computer or terminal. But [Make it Kozi] wanted an old-fashioned typewriter. The problem is, as he notes, they are nostalgically popular these days, so picking up a working model can be pricey. The answer? Buy a junker and restore it. You can watch the whole process in the video below, too, but nearly the only sound you’ll hear is the clacking of the keys. He doesn’t say a word until around the 14-minute mark. Just warning you if you have it playing in the background!

Of course, even if you can find a $10 typewriter, it probably won’t be the same kind, nor will it have the same problems. However, it is a good bet that any old mechanical typewriter will need many of the same steps.

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1950s Switching Power Supply Does It Mechanically

April 8, 2024 by 26 Comments

When you hear about a switching power supply, you think of a system that uses an inductor and a switch to redistribute energy from the input to the output. But the original switching power supply was the vibrator supply, which was common in automotive applications back in the middle part of the last century. [Mr. Carlson] has a 1950s-era example of one of these, and he invites us to watch him repair it in the video below.

Most of the vibrator supplies we’ve seen have been built into car radios, but this one is in a box by itself. The theory is simple. A DC voltage enters the vibrator, which is essentially a relay that has a normally-closed contact in series with its coil. When current flows, the relay operates, breaking the contact. With no magnetic field, the springy contact returns to its original position, allowing the whole cycle to repeat.

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Fixing An Expensive Smart Toaster Is Worth The Time

April 7, 2024 by 49 Comments

There was a time when the simplest and cheapest kitchen appliance you could think of was a toaster. Some nichrome wire, a spring, and a mechanical thermostat were all you needed. Those days are gone and today’s toasters are full of special features, network connections, and fancy cases.

Take [boilerbot]’s Breville die-cast smart toaster. The four-slice model is upwards of $200. As Star Trek’s [Mr. Scott] said, “The more they overthink the plumbing, the easier it is to stop up the drain.” That seems to be the case here. The toaster failed and while [boilerbot] did fix it, he got lucky. He mentions that if the damage had been lower in the toaster, getting to it would have been nearly impossible.

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Comparing Desoldering Tools

April 7, 2024 by 27 Comments

[Lee] has a Hakko FR301 desoldering gun and a Duratool knockoff. He freely admits that the Hakko is probably better, but he wonders if it’s good enough to justify being four times as expensive. He shows both of them off in a recent video that you can see below.

Often, desoldering doesn’t get as much attention as soldering, but for repairs or if you make mistakes —  and who doesn’t — it is an essential skill. Many of the differences will be either good or bad, depending on your personal preference. For example, the Hakko is an all-in-one unit, so it doesn’t have a bulky box to sit on your bench. However, that also means the Hakko is larger and heavier. It also lacks controls and indicators the other unit has on the base station box.

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Inside A Hisense TV Repair Attempt

April 6, 2024 by 18 Comments

Many of us misspent our youth fixing televisions. But fixing a 1970s TV is a lot different than today — the parts were big and tubes were made to be replaced. Have you torn into a big flat screen lately? It is a different world, as [The Fixologist] shows us in the video below.

The TV in question was rescued from a neighbor who was about to throw it away. If you are like us, you’ll watch the first few minutes and see it powers up, but the screen is very dark. Back light problem, right? No problem. But it turned out to be more than we thought.

Honestly, we assumed it might be the power supply, and we would have put a power supply on the LED leads to test that first. That would have been smart because taking the panel off to reveal the LEDs was very difficult! There were two bad LEDs, though, so in the end you’d have had to do it anyway.

We were disappointed that after fixing the LED, he cracked the LCD panel during the reinstallation. So, in the end, this was more of a teardown video and not a repair video. He seemed to think a lot of the tape in the unit was to thwart repairs. That could be, but we wondered if it made manufacturing the TV easier which, after all, is mostly what they care about.

This isn’t the first time we’ve heard people tearing into a TV and wondering if the factory was against them. We’ve considered it, but we are pretty sure it isn’t the case.

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DIY 6 GHZ Pulse Compression Radar

April 6, 2024 by 10 Comments

Conceptually, radar is pretty simple: send out a radio wave and time how long it takes to get back via an echo. However, in practice, there are a number of trade-offs to consider. For example, producing a long pulse has more energy and range, but limits how close you can see and also the system’s ability to resolve objects that are close to each other. Pulse compression uses a long transmission that varies in frequency. Reflected waves can be reconstituted to act more like a short pulse since there is information about the exact timing of the reflected energy. [Henrik] didn’t want to make things too easy, so he decided to build a pulse compression radar that operates at 6 GHz.

In all fairness, [Henrik] is no neophyte when it comes to radar. He’s made several more traditional devices using a continuous wave architecture. However, this type of radar is only found in a few restricted applications due to its inherent limitations. The new system can operate in a continuous wave mode, but can also code pulses using arbitrary waveforms.

Some design choices were made to save money. For example, the transmitter and receiver have limited filtering. In addition, the receiver isn’t a superheterodyne but more of a direct conversion receiver. The signal processing is made much easier by using a Zynq FPGA with a dual-core ARM CPU onboard. These were expensive from normal sources but could be had from online Chinese vendors for about $17. The system could boot Linux, although that’s future work, according to [Henrik].

At 6 GHz, everything is harder. Routing the PCB for DDR3 RAM is also tricky, but you can read how it was done in the original post. To say we were impressed with the work would be an understatement. We bet you will be too.

Radar has come a long way since World War II and is in more places than you might guess. We hate to admit it, but we’d be more likely to buy a ready-made radar module if we needed it.