Magazine Transistor Tester Lives Again

October 27, 2025 by 9 Comments

One of the lost pleasures of our modern world is the experience of going shopping at a grocery store, a mall, or a drugstore, and finding this month’s electronics magazine festooned with projects that you might like to build. Sure, you can find anything on the Internet, but there’s something to be said about the element of surprise. Can any of those old projects still be of interest?

[Bettina Neumryr] thinks so. She has a hobby of finding old magazine projects and building them. Her most recent installment is a transistor tester from the June 1983 issue of Everyday Electronics.

The tester was quite a neat job for 1983, with a neat case and a PC board. It measures beta and leakage. There’s an analog meter that can measure the collector current for a fixed base current (beta or hfe). Leakage is how much current flows between emitter and collector with the base turned off.

In 1983, we’d have loved to have a laser printer to do toner transfer for the PC board, but of course, that was unheard of in hobby circles of the day. The tester seemed to work right off the bat, although there was a small adjustment necessary to calibrate the device. All that was left was to put it in a period-appropriate box with some printed labels.

We loved the old electronics and computer magazines. Usually, when we see someone working on an old magazine project, it is probably not quite a literal copy of it. But either way is cool.

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Record-Breaking Robots At Guinness World Records

October 26, 2025 by 12 Comments

If you ever wanted to win a bar bet about a world record, you probably know about the Guinness book for World Records. Did you know, though, that there are some robots in that book? Guinness pointed some out in a recent post.

Ever wonder about the longest table-tennis rally with a robot or the fastest robotic cube solver? No need to wonder anymore.

Our favorite was the fastest robot to solve a puzzle cube. This robot solved the Rubik’s Cube in 103 milliseconds! Don’t blink or you’ll miss it in the video embedded. Of course, the real kudos go to the team that created the robot: [Matthew Patrohay], [Junpei Ota], [Aden Hurd], and [Alex Berta].

Another favorite was the smallest humanoid robot. In order to win this record, the robot must be able to move its shoulders, elbows, knees, and hips just like a human. It also has to be able to walk on two feet. This tiny little guy meets the requirements and stands only 57.6 mm (2.26 in) tall! Created by [Tatsuhiko Mitsuya] in April 2024, this robot can be controlled via Bluetooth.

We’ve seen entries in this category before — check them out in Almost Breaking The World Record For The Tiniest Humanoid Robot, But Not Quite.

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VFETs Are (Almost) Solid State Tubes

October 26, 2025 by 9 Comments

We always enjoy videos from [w2aew]. His recent entry looks at vertical or VFETs, which are, as he puts it, a JFET that thinks it is a triode. He clearly explains how the transistor works as a conductor unless you bias the gate to form a depletion zone.

The transistors have a short channel, which means they conduct quite well. The low gate resistance and capacitance mean the devices can also switch very quickly. These devices were once in vogue for audio applications. However, they’d fallen out of favor until recently. The reason is that they work quite well in switching power supplies.

How good is the on resistance? So good that his meter reported the probes were shorted instead of measuring the resistance. Pretty good. We’ve seen these VFET transistors used as switches to drive magnetic field coils many years ago and they replaced much more complex circuitry.

The curve tracer in the video is a beautiful instrument of its own. The digital displays give it a high tech yet retro look. A curve tracer, if you haven’t used one, plots stepped voltages against current flowing, and is very useful for examining semiconductor devices. While not as fancy, it is possible to make one to connect to a scope quite easily.

We are pretty sure that it is a Tektronix 576. We watched a repair of a similar unit, the 577, if you’d like to see some (probably) similar insides.

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Hackaday Links: October 26, 2025

October 26, 2025 by 11 Comments

There was a bit of a kerfuffle this week with the news that an airliner had been hit by space junk. The plane, a United Airlines 737, was operating at 36,000 feet on a flight between Denver and Los Angeles when the right windscreen was completely shattered by the impact, peppering the arm of one pilot with bits of glass. Luckily, the heavily reinforced laminated glass stayed intact, but the flight immediately diverted to Salt Lake City and landed safely with no further injuries. The “space junk” report apparently got started by the captain, who reported that they saw what hit them and that “it looked like space debris.”

We were a little skeptical of this initial assessment, mainly because the pilots and everyone aboard the flight were still alive, which we’d assume would be spectacularly untrue had the plane been hit by anything beyond the smallest bit of space junk. As it turns out, our suspicions were justified when Silicon Valley startup WindBorne Systems admitted that one of its high-altitude balloons hit the flight. The company, which uses HABs to gather weather data for paying customers, seems to have complied with all the pertinent regulations, like filing a NOTAM, so why the collision happened is a bit of a mystery.

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Examining The First Mechanical Calculator

October 26, 2025 by 9 Comments

Blaise Pascal is known for a number of things, but we remember him best for the Pascaline, an early mechanical calculator. [Chris Staecker] got a chance to take a close look at one, which is quite a feat since there were only about 20 made, and today we only know where nine of them wound up.

This Pascaline was lost for many years, and turned up in an antique store, where they thought it was a music box of some kind. The recent owner passed away, and now this machine is going to go up for auction, probably for more than we can afford. While he wasn’t able to handle the antique, he has plenty of knock-offs that were made back when people actually used them, which wasn’t that long ago. One of these is transparent, so you can see the mechanism inside.

The idea is to use the wheels like an old-fashioned phone dial to add counts to an output wheel. A linkage moves the next input wheel every time the current output wheel passes nine. Of course, if you have a multi-digit carry, it might take a little more elbow grease than just flipping the dial one normal position.

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A 2D simple regression analysis.

Making Math Less Stressful With A Python Super-Calculator

October 26, 2025 by 15 Comments

In a recent write-up, [David Delony] explains how he built a Wolfram Mathematica-like engine with Python.

Core to the system is SymPy for symbolic math support. [David] said being able to work with symbolic math easily has helped his understanding of calculus and linear algebra. For statistics support he includes NumPy, pandas, and SciPy. NumPy is useful for creating multidimensional arrays and supports basic descriptive statistics such as mean, median, and standard deviation; pandas is a library for operating on tabular data arranged into “DataFrames”, it can load data from spreadsheets (including Excel) and relational databases; and SciPy is a “grab bag” of operations designed for scientific computing, it includes some useful statistics operations, including common probability distributions, such as the binomial, normal, and Student’s t-distribution.

For regression analysis [David] includes statsmodels and Pingouin. If you’re not familiar with the term “regression analysis” it basically refers to the process of curve fitting. When your data is two-dimensional, with one dependent variable, the simple linear regression algorithm will generate a function that fits the data as y = mx + b, including the slope (m) and the y-intercept (b); this can be extrapolated to higher dimensional data and other types of regression.

If you have an interest in symbolic math you might enjoy learning about Mathematica And Wolfram On The Raspberry Pi.

Spreadsheets Apple ][ Style

October 26, 2025 by 9 Comments

It is hard to remember a time when no one had a spreadsheet. Sure, you had big paper ledgers if you were an accountant. But most people just scribbled their math on note paper or, maybe, an engineering pad. [Christopher Drum] wanted to look at what the state of the art in 1978 spreadsheet technology could do. So he ran VisiCalc.

Surprisingly, VisiCalc got a lot of things right that we still use today. One thing we don’t see much of is the text-based menu. As [Christopher] puts it, when you press the slash key, “what first appears to be ‘the entire alphabet’ pops up at the top of the screen.” In reality, it is a menu of letters that each correspond to some command. For example, C will clear the sheet (after prompting you, of course).

Interestingly, VisiCalc of the day didn’t do a natural order of evaluation. It would process by rows or by columns, your choice. So if cell A1 depended on cell B5, you’d probably get a wrong answer since A1 would always be computed before B5. Interestingly, the old Apple didn’t have up and down keys, so you had to toggle what the right and left keys did using the space bar. Different times!

This is a great look into a very influential piece of software and its tutorials. If you have old VisiCalc files you want to drag into the 21st century, [Christopher] explains the convoluted process to get mostly there.

We’ve been known to abuse spreadsheets pretty badly, although we’ve seen worse.