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592 Articles

The Perils Of Return Path Gaps

March 15, 2024 by 9 Comments

The radio frequency world is full of mysteries, some of which seem to take a lifetime to master. And even then, it seems like there’s always something more to learn, and some new subtlety that can turn a good design on paper into a nightmare of unwanted interference and unexpected consequences in the real world.

As [Ken Wyatt] aptly demonstrates in the video below, where you put gaps in return paths on a PCB is one way to really screw things up. His demo system is simple: a pair of insulated wires running from the center pins on BNC jacks and running along the surface of a piece of copper-clad board to simulate a PCB trace. The end of each wire is connected to the board’s ground plane through a 50 ohm resistor, with one wire running over a narrow slot cut into the board. A harmonics-rich signal is fed into each trace while an H-field EMC probe connected to a spectrum analyzer is run along the length of the trace.

With the trace running over the solid ground plane, the harmonics are plentiful, as expected, but they fall off very quickly away from the trace. But over on the trace with the gapped return trace it’s a far different story. The harmonics are still there, but they’re about 5 dBmV higher in the vicinity of the gap. [Ken] also uses the probe to show just how far from the signal trace the return path extends to get around the gap. And even worse, the gap makes it so that harmonics are detectable on the unpowered trace. He also uses a current probe to show how common-mode current will radiate from a long conductor attached to the backplane, and that it’s about 20 dB higher with the gapped trace.

Hats off to [Ken] for this simple explanation and vivid reminder to watch return paths on clock traces and other high-frequency signals. Need an EMC probe to check your work? A bit of rigid coax and an SDR are all you need.  Continue reading “The Perils Of Return Path Gaps” →

Educational Arduino Clock Uses Analog Meters For Display

March 1, 2024 by 13 Comments

When it comes to educational electronic projects, it’s hard to go past building a clock. You learn tons about everything from circuit concepts and assembly skills to insights about the very nature of time itself. And you get a clock at the end of it! [hamblin.joe] wanted to do a simple project for kids along these lines, so whipped up a neat design using analog meters to display the time.

The build relies on that old stalwart, the Arduino Uno, to run the show. It’s hooked up to a DS3231 real-time clock module so it can keep accurate time for long periods, as is befitting a clock. Displaying the time is done via the use of two analog meters, each fitted with a custom backing card. One displays hours, the other, minutes. The analog meters are simply driven by the PWM outputs of the Arduino.

It’s not a hugely complex project, but it teaches so much. It provides an opportunity to educate the builders about real-time clocks, microcontroller programming, and even the concepts behind pulse width modulation. To say nothing of the physical skills, like learning to solder or how to assemble the laser-cut enclosure. Ultimately, it looks like a really great way for [hamblin.joe] and his students to dive into the world of modern electronics.

Pi Pico Enhances RadioShack Computer Kit

February 20, 2024 by 9 Comments

While most of us now remember Radio Shack as a store that tried to force us to buy batteries and cell phones whenever we went to buy a few transistors and other circuit components, for a time it was an innovative and valuable store for electronics enthusiasts before it began its long demise. Among other electronics and radio parts and kits there were even a few DIY microcomputers, and even though it’s a bit of an antique now a Raspberry Pi Pico is just the thing to modernize this Radio Shack vintage microcomputer kit from the mid 80s.

The microcomputer kit itself is built around the 4-bit Texas Instruments TMS1100, one of the first mass-produced microcontrollers. The kit makes the processor’s functionality more readily available to the user, with a keypad and various switches for programming and a number of status LEDs to monitor its state. The Pi Pico comes into the equation programmed to act as a digital clock with an LED display to drive the antique computer. The Pi then sends a switching pulse through a relay to the microcomputer, which is programmed as a binary counter.

While the microcomputer isn’t going to win any speed or processing power anytime soon, especially with its clock signal coming from a slow relay module, the computer itself is still fulfilling its purpose as an educational tool despite being nearly four decades old. With the slow clock speeds it’s much more intuitive how the computer is stepping through its tasks, and the modern Pi Pico helps it with its tasks quite well. Relays on their own can be a substitute for the entire microcontroller as well, like this computer which has a satisfying mechanical noise when it’s running a program.

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An Apple ][ With A Pendulum

February 5, 2024 by 6 Comments

Clocks are a favourite project here, and we can say we’ve seen all conceivable types over the years. Just a software clock on a retrocomputer perhaps isn’t the coolest among them, but [Willem van der Jagt ]’s Apple][ clock has a little bit extra. It takes its time reference from a real pendulum, on an antique wall clock.

A proximity sensor next to a metal pendulum gives an easy way to generate a digital pulse on each pass, but leaves the question of how to transfer it to the computer. With computers of this age the circuitry is surprisingly simple, and in this case he’s sending an interrupt to the machine which the software can pick up for its timing. There is a small logic circuit between the sensor and the interrupt allowing him to gate the pendulum line, triggered from one of the output lines exposed on the Apple’s game port.

The code is written in assembly, and counts the number of pendulum swings before incrementing the number of minutes. It’s an enjoyable reminder of the days when the architecture of a computer was this accessible, and for those of us whose past lies in the Sinclair world it’s also been a little peek into something of how the Apple works.

We think this is the first pendulum-driven retrocomputer clock we’ve seen here at Hackaday, as you might understand when a clock has a pendulum it’s usually a more traditional design.

Resistor Color Code Clock Is A Bit Of Fun

February 3, 2024 by 6 Comments

Younger electronic engineers may see resistors with old-style color codes to display their values a little less than those from previous years, but if there’s a shibboleth among those who wield a soldering iron it’s probably something similar to instinctively saying “1K” when asked “Brown-black-red?”. Colors as numbers can be used outside resistors, for example in a clock, as [Det Builds Stuff] shows us with an ESP32 TFT dev board.

It’s fair to say that this is more of a software project than a hardware one, but that’s not necessarily a bad thing as he takes us though the process of creating a Network Time Protocol (NTP) capable clock with the dev board. He claims it may be the world’s first resistor clock, something we’d have to disagree with, but beside that we can see this could make a neat little desk ornament with a 3D printed case.

Oddly though, we’d expect older engineers to face the same steep learning curve as younger ones when reading it, because it’s easier to recognize visual sequences of numbers as preferred resistor values than it is to visually decode each one every time.

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Neon Watch Glows Rather Nicely, Tells Time

January 17, 2024 by 12 Comments

It wasn’t long after the development of the LED that LED watches became available. They were prized for their clear light output and low power draw. Neon bulbs, on the other hand, are thirsty for current and often warm or even hot in operation. And yet, [Lucas] found a way to build them into a sweet watch that actually does the job. Nice, right?

The design uses a simple trick to avoid killing the batteries with excessive power draw. The neon lamps are only activated when the user waves a hand above the watch, at which point the lamps light to display the time. Reading the time is  a little fiddly, but understandable with the aid of this PDF diagram. Basically, the two electrodes of each neon lamp are driven independently. This gives each of the four lamps three possible states: with the first electrode lit, the second electrode lit, or both lit. Four lamps multiplied by three states equals 12—so the watch can display the hour quite easily. As for minutes, a similar scheme is used with some modifications for clarity. Setting the time is via a light sensor on the watch which picks up flashes from a computer screen.

It reminds us of a time when we once thought nixie tubes were too power hungry for a wristwatch build… until the hackers of the world proved us wrong. Video after the break.

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Kinetic Clock Is A Clean Modern Way To Tell Time

January 16, 2024 by 11 Comments

Hackers and makers aren’t usually too interested in basic round analog clocks. They tend to prefer building altogether more arcane and complicated contraptions to display numbers for the telling of time. [alstroemeria] did just that with this nifty kinetic clock build.

The basic concept of the kinetic clock is to have a flat plate, which individual segments raise out of to create a physical (instead of illuminated) 7-segment display. This is achieved with servos which push the segments in and out using a small rack mechanism. It’s not a sophisticated build; it simply uses 30 servos to handle all the segments needed to tell time. Thus, the Arduino Mega was the perfect tool for the job. With a sensor shield added on, it has an abundance of IO, driving a ton of servos is a cinch. There’s also a DS3231 real time clock to help it keep accurate time.

Incidentally, it’s a hefty thing to print, according to YouTuber [Lukas Deem] who replicated the project. It took around 85 hours to print, and a total of 655 grams of filament – not counting mistakes and trashed parts.

And if you think you’re having deja-vu, you might well be. We’ve seen a take on this exquisite design before. We liked it then, and we like it now.

Overall, it’s a stylish build that looks as good as your 3D printer’s output will allow. A resin printer would be a massive boon in this regard. Video after the break.

Continue reading “Kinetic Clock Is A Clean Modern Way To Tell Time” →