Author: Al Williams

4460 Articles

How Many Time Zones Are There Anyway?

February 14, 2024 by 38 Comments

Nowadays, it’s an even bet that your newest project somehow connects to the Internet and, thus, to the world. Even if it doesn’t, if you share your plans, someone might reproduce your creation in some far distant locale. If your design uses time, you might need to think about time zones. Easy, right? That’s what [Zain Rizvi] thought until he tried to deploy something that converted between timezones. You can learn from his misconceptions thanks to a detailed post he provides.

You might think, “What’s the big deal?” After all, there’s UTC, and then there are 12 time zones ahead of UTC and 12 time zones later. But that’s not even close to true.

As [Zain] found out, there are 27 hours in a full-day cycle if you count UTC as one hour. Why? Because some islands in the Pacific wanted to be on the wrong side of the International Date Line. So there are a few extra zones to accommodate them.

You can’t even count on time zones being offset by an hour from the previous zone. Several zones have a half-hour offset from UTC (for example, India’s standard time is 5.5 hours from UTC). But surely the offset is always either a whole number or a number where the fractional part is 0.5, right?

Um, no. Nepal wants the sun to be directly over the mountain at noon, so it offsets by 45 minutes! [Zain] wonders — as we do — what would happen if the mountain shifted over time? Until 1940, Amsterdam used a 20-minute offset. Some cities are split with one half in one time zone and another in the other.

Of course, there are the usual problems with multiple names for each zone, both because many countries want their own zone and because the exact same zone is different in different languages. Having your own zone is not just for vanity, though. Daylight savings time rules will vary by zone and even, in some cases, only in certain parts of a zone. For example, in the United States, Arizona doesn’t change to daylight savings time. Oh, except for the Navajo Nation in Arizona, which does! Some areas observe daylight savings time that starts and ends multiple times during the year. Even if you observe daylight savings time, there are cases where the time shift isn’t an entire hour.

Besides multiple names, common names for zones often overlap. For example, in the United States, the Eastern Standard Time zone differs from Australia’s. Confused? You should be.

Maybe we should have more respect for multiple time zone clock projects. We’ve noticed these problems before when we felt sorry for the people who maintain the official time zone database.

Tandy Pocket Computer Assembly Is… Weird

February 12, 2024 by 21 Comments

Radio Shack had a long history of buying things overseas, having their name slapped on them, and selling them in the United States. That was the case with the Tandy Pocket Computers, which were in that awkward space between calculators and full-blown computers. Like many computers of those days, if you wanted to do anything interesting, you needed to turn to assembly language. But as [Old Vintage Computing Research] recalls, the assembly for these little devices was very strange, even for an assembly language. He found out that there is a reason it is so strange and shares it in a deep dive into the device’s machine code history.

The story starts with the Japanese government. In 1969, the ministry in charge of such things decided that it wouldn’t be fair for people who knew a particular computer to have an advantage when taking the Information Technology Engineer exam. So, logically, they made up a fictitious instruction set and architecture for the test. Since no one used it, no one would have an unfair advantage.

However, eventually, Japanese manufacturers started making computers that used the architecture. The architecture was COMP-X, and the assembler was CAP-X. The post covers the history of machines either using the architecture or emulating it going back to the 1970s. It eventually winds up at the Sharp and Casio pocket computers that would wear Radio Shack livery in much of the world, especially the United States.

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Printing A Log

February 11, 2024 by 16 Comments

We’ve used wood filament before, and we hazily remember a Cura plugin that changed temperatures to create wood grain. But unlike [Patrick Gibney], we never thought of printing a faux wood log coaster that looks like it has rings. Check out the video below to see how it works.

The filament is not really wood, of course, but a polymer — usually PLA — mixed with wood particles. Changing the temperature does a nice job of darkening the wood. However, it also changes the properties of the carrier polymer, and that’s not always a good thing.

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3D Printed DIN Rail Mount Is Attractive

February 11, 2024 by 8 Comments

DIN rails aren’t very common in hobby projects, although you do see them occasionally. But in some industries, they are everywhere. The rail is just a piece of aluminum or steel with slots to hold it to a wall or bulkhead. There are two small lips that equipment like circuit breakers, power supplies, or controllers can attach easily. A common 3D printing project is a way to mount something like a printer controller to DIN rails. [NotLikeALeafOnThe Wind] shows a different take on it: a magnetic holder that temporarily attaches a rail to a ferrous surface.

Of course, mounting the rail is only half the equation. After that, you still need things to mount on the rail. Luckily, there’s no shortage of designs for DIN mounts for many common boards and modules.

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Analog Engineer’s Pocket Reference Needs A Big Pocket

February 10, 2024 by 24 Comments

We always admire when companies produce useful tools or documentation that aren’t specific to their products. For example, consider LTSpice. Sure, it has the company’s models baked in. But there’s no reason you can’t use it for anything. Thanks! We were interested to see Texas Instrument’s fifth edition of the “Analog Engineer’s Pocket Reference” is still freely available. While we aren’t sure a book with nearly 200 pages in it is a “pocket reference,” we do think you’ll enjoy it, even if you don’t want to use TI’s offerings. This book has been around for 50 years, but it is updated periodically, and this version is the fifth iteration.

The book has several sections ranging from conversion between units and color codes to amplifier noise calculations and understanding ADC settling times. Want to know more about PCB microstrips? Page 85.

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Wooden Desk Lamp Uses Unusual Dimmer

February 10, 2024 by 11 Comments

One of the problems with laser cutting projects is that while they look good, they often look like they were laser cut. [Timber Rough] has a wooden desk lamp that not only looks good but has one of the most unusual dimming features we’ve seen.

One thing that stands out is the lamp is made of different kinds of wood, and that helps. But the dimmer is a magnet and Hall effect sensor that levitates. It is hard to explain, but a quick look at the video below will clarify it.

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Simple Magnetic Levitator

February 10, 2024 by 9 Comments

[Stoppi] always has exciting projects and, as you can see in the video below, the latest one is a very simple magnetic levitator design. The design is classic and simple: a 5 V regulator IC, a Hall effect sensor, a 741 op amp, and a MOSFET to turn the electromagnet on and off.

Sure, there are a few passive components and a diode, too, but nothing exotic. The sensor normally presents 2.5 V of output. The voltage rises or drops depending on the polarity of the magnetic field. The stronger the field, the more the voltage changes away from the 2.5 V center.

The op amp acts as a comparator with a potentiometer setting the trip point. As the ball moves up towards the coil, the voltage increases, triggering the comparator, which turns off the FET. With no current through the coil, there’s no more electromagnet, and the ball starts to fall.

Of course, as the ball falls, the voltage from the sensor also drops, and this eventually turns on the electromagnet. The ball eventually reaches a relatively stable position.

This is one of those cases where a simple analog circuit might work better than a digital one. Or make it hard on yourself and use an FPGA.

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