RF Spectrometer Sees Inside

January 30, 2023 by Al Williams 7 Comments

Spectrometry is a well-known technique or, more correctly, a set of techniques. We usually think of it as the analysis of light to determine what chemicals are producing it. For example, you can tell what elements are in a star or an incandescent based on the spectrum of light they emit. But you can also do spectroscopy with other ranges of electromagnetic radiation. [Applied Science] shows how to make an RF spectroscope. You can see the video below.

An oscilloscope-resident function generator creates a signal that he feeds to an amplifier because you need a fair amount of power going out. However, you also need to sense a very tiny amount of power coming back, and that requires a special circuit that will block high-power signals while passing low-level signals.

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Retro Gadgets: The CB Cell Phone

January 30, 2023 by Al Williams 45 Comments

There was a time when one of the perks of having a ham radio in your car (or on your belt) was you could make phone calls using a “phone patch.” In the 1970s, calling someone from inside your parked car turned heads. Now, of course, it is an everyday occurrence thanks to cell phones. But in 1977, cell phones were nowhere to be found. Joseph Sugarman, the well-known founder of JS&A, saw a need and wanted to fill it. So he offered the “PocketCom CB” which was billed as the “world’s smallest citizens band transceiver.” You can see the full-page ad from 1977 below.

Remember that this is from an era when ICs that could operate at 30 MHz were not the norm, so you have to temper your expectations. The little unit was 5.5 in by 1.5 in and less than an inch thick. That’s actually not bad, but you had — optimistically — 100 mW of output power. They claimed the N cell batteries would last two weeks with average use, but we imagine a lot less as soon as you start transmitting. The weight was 5 oz, but we suspect that is without the batteries.

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Inside A 1940’s Spy Radio

January 30, 2023 by Al Williams 18 Comments

The RCA CR-88 was a radio receiver made to work in top-secret government eavesdropping stations. As you might expect, these radios are top-of-the-line, performance-wise, at least when they are working correctly. [Mr. Carlson] has one on his bench, and we get to watch the show on his recent video that you can see below.

Interestingly, [Mr. Carlson] uses some Sherlock Holmes-like deductive reasoning to guess some things about the radio’s secret history. The radio’s design is decidedly heavy-duty, with a giant power transformer and many tubes, IF transformers, and large filter capacitors.

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The Times They Are A-Chaining

January 28, 2023 by Al Williams 6 Comments

If [Bob Dylan] had seen [Pgeschwi]’s bike chain clock, it might have influenced the famous song. The clock uses a stepper motor and a bike chain to create a clock that has a decidedly steampunk vibe. Despite the low-tech look, the build uses 3D printing and, of course, a bike chain.

The clock doesn’t just show the time. There is a contraption to show the day of the week, and a pendulum shows the current phase of the moon. The visible wiring is all old-school brass wire on the wood base. [Pgeschwi] is considering changing out all the 3D printed parts for brass ones, so this may be just an early prototype of the final product, but it still looks great.

The design used common tools, including Tinkercad and an online gear generation tool. There are a lot of details you wouldn’t suspect until you tried to build something like this yourself. For example, making the chain reliably go in both directions required a timing belt to synchronize the top gears. Getting the numbers on the chain to pass by the gears.

It is hard to tell from the picture, but there’s an LED under the 10-minute marks that shows the unit’s digits of the time. There are no markings for it yet, but in the picture, the time is actually 4:09.

We love unusual clocks, and we see plenty of them. From Fibonacci clocks to magnetic field line clocks, we love them all.

Better Macro Images With Arduino Focus Stacking

January 26, 2023 by Al Williams 17 Comments

If you’ve ever played around with macro photography, you’ve likely noticed that the higher the lens magnification, the less the depth of field. One way around this issue is to take several slices at different focus points, and then stitch the photos together digitally. As [Curious Scientist] demonstrates, this is a relatively simple motion control project and well within the reach of a garden-variety Arduino.

You can move the camera or move the subject. Either way, you really only need one axis of motion, which makes it quite simple. This build relies on a solid-looking lead screw to move a carriage up or down. An Arduino Nano acts as the brains, a stepper motor drives the lead screw, and a small display shows stats such as current progress and total distance to move.

The stepper motor uses a conventional stepper driver “stick” as you find in many 3D printers. In fact, we wondered if you couldn’t just grab a 3D printer board and modify it for this service without spinning a custom PCB. Fittingly, the example subject is another Arduino Nano. Skip ahead to 32:22 in the video below to see the final result.

We’ve seen similar projects, of course. You can build for tiny subjects. You can also adapt an existing motion control device like a CNC machine.

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Toxic Telescope Makes You Mad As A Hatter

January 25, 2023 by Al Williams 51 Comments

[Hank Green] posted an interesting video about the first liquid mirror telescope from back in the 1850s. At the time, scientists were not impressed. But, these days, people are revisiting the idea. The big problem with the early telescope is that it used mercury. Mercury is really bad for people and the environment.

The good thing about a liquid scope is that you can pretty easily make a large mirror. You just need a shallow pool of liquid and a way to spin it. However, there are downsides. You need to isolate the liquid from vibrations and dust. Another downside is that since gravity makes the shape of the mirror, these telescopes only go one way — straight up.

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I’ve Been Printing On The Dragon Railroad…

January 25, 2023 by Al Williams 28 Comments

We know many people who put much effort into building model train setups. But [Rambros] has an entire set 3D printed, and the files are open source, so you can print your own or modify it to suit you. When we first read “complete open source ecosystem,” we thought it might have been a bit of hyperbole, but it isn’t. The S-scale set includes two locomotives, a tanker, a box car, a hopper car, and a gondola car. There are different sections of track, customizable with Fusion 360. The “Dragon Railway” takes a few mechanical parts and electronics, of course. You can see one of several videos about the system below.

You can control the whole system using Bluetooth and a smartphone. The electronics are pretty simple, consisting of an ESP32 board, some motor drivers, N20 motors, and a few miscellaneous parts. We expect it would be compatible with other off-the-shelf S scale tracks and cars, but we don’t know that for sure.

Although you’ll need Fusion 360 to customize, there are plenty of ready-made STL files if you want to get started quickly. Some of the track items, like the crossing and turnout are not customizable, anyway. One particularly impressive item is a printed auto-coupler; while a small item, getting that to work reliably with printed parts seems like it may be the most difficult part of the whole thing.

Maybe an OLED display would be the next thing? We’ve seen other printed trains, but this seems like a real labor of love.

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