Mechanical 7-Segment Display Combines Servos And Lego

June 25, 2025 by 4 Comments

If you need a seven-segment display for a project, you could just grab some LED units off the shelf. Or you could build something big and electromechanical out of Lego. That’s precisely what [upir] did, with attractive results.

The build relies on Lego Technic parts, with numbers displayed by pushing small black axles through a large yellow faceplate. This creates a clear and easy to read display thanks to the high contrast. Each segment is made up of seven axles that move as a single unit, driven by a gear rack to extend and retract as needed. By extending and retracting the various segments in turn, it’s possible to display all the usual figures you’d expect of a seven-segment design.

It’s worth noting, though, that not everything in this build is Lego. The motors that drive the segments back and forth are third-party components. They’re Geekservo motors, which basically act as Lego-mountable servos you can drive with the electronics of your choice. They’re paired with an eight-channel servo driver board which controls each segment individually. Ideally, though, we’d see this display paired with a microcontroller for more flexibility. [upir] leaves that as an exercise for the viewer for now, with future plans to drive it with an Arduino Uno.

Design files are on Github for the curious. We’ve featured some similar work before, too, because you really can build anything out of Lego. Video after the break.

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IOT 7-segment display

Modern Tech Meets Retro 7-Segment

June 23, 2025 by 7 Comments

At one point in time mechanical seven segment displays were ubiquitous, over time many places have replaced them with other types of displays. [Sebastian] has a soft spot for these old mechanically actuated displays and has built an open-source 7-segment display with some very nice features.

We’ve seen a good number of DIY 7-segment displays on this site before, the way [Sebastian] went about it resulted in a beautiful well thought out result. The case is 3D printed, and although there are two colors used it doesn’t require a multicolor 3d printer to make your own. The real magic in this build revolves around the custom PCB he designed. Instead of using a separate electromagnets to move each flap, the PCB has coil traces used to toggle the flaps. The smart placement of a few small screws allows the small magnets in each flap to hold the flap in that position even when the coils are off, greatly cutting down the power needed for this display. He also used a modular design where one block has the ESP32 and RTC, but for the additional blocks those components can remain unpopulated.

The work he put into this project didn’t stop at the hardware, the software also has a great number of thoughtful features. The ESP32 running the display hosts a website which allows you to configure some of the many features: the real-time clock, MQTT support, timer, custom API functions, firmware updates. The end result is a highly customizable, display that sounds awesome every time it updates. Be sure to check out the video below as well as his site to see this awesome display in action. Also check out some of the other 7-segment displays we’ve featured before.

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Retrotechtacular: 1970s Radio

June 21, 2025 by 10 Comments

Before YouTube, you had to watch your educational videos on film. In the 1970s, if you studied radio, you might have seen the video from Universal Education and Visual Arts, titled Understanding Electronics Basic Radio Circuitry. The video’s been restored, and it appears on the [CHAP] YouTube channel.

The video starts with a good history lesson that even covers Fessenden, which you rarely hear about. The video is full of old components that you may or may not remember, depending on your age. There’s a classic crystal radio at the start and it quickly moves to active receivers. There’s probably nothing in here you don’t already know. On the other hand, radios work about the same today as they did in the 1970s, unless you count software-defined varieties.

We expect this was produced for the “trade school” market or, maybe, a super advanced high school shop class. There were more in the series, apparently, including ones on vacuum tubes, the transistor, and the principles of television.

We were sad that the credits don’t mention the narrator. He sounded familiar. Maybe Robert Vaughn? Maybe not. A little research indicates the company was a division of Universal Studios, although the Library of Congress says it was actually produced by  Moreland-Latchford Productions in Toronto.

Maybe these videos were the next step in becoming a child radio engineer. If you like old radio videos, this one is even older.

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Cassette Data Storage From The 1970s

June 13, 2025 by 69 Comments

When home computers first appeared, disk drives were an expensive rarity. Consumers weren’t likely to be interested in punch cards or paper tape, but most people did have consumer-grade audio cassette recorders. There were a few attempts at storing data on tapes, which, in theory, is simple enough. But, practically, cheap audio recorders are far from perfect, which can complicate the situation.

A conference in Kansas City settled on a standard design, and the “Kansas City standard” tape format appeared. In a recent video, [Igor Brichkov] attempts to work with the format using 555s and op amps — the same way computers back in the day might have done it. Check out the video below to learn more.

These days, it would be dead simple to digitize audio and process it to recover data. The 1970s were a different time. The KC standard used frequency shift method with 2.4 kHz tones standing in for ones, and 1.2 kHz tones were zeros. The bit length was equal (at 300 baud), so a one had 8 cycles and a zero had 4 cycles. There were other mundane details like a start bit, a minimum stop bit, and the fact that the least significant bit was first.

The real world makes these things iffy. Stretched tape, varying motor speeds, and tape dropouts can all change things. The format makes it possible to detect the tones and then feed the output to a UART that you might use for a serial port.

There were many schemes. The one in the video uses an op-amp to square up the signal to a digital output. The digital pulses feed to a pair of 555s made to re-trigger during fast input trains but not during slower input trains. If that doesn’t make sense, watch the video!

The KC standard shows up all over the place. We’ve even used it to hide secret messages in our podcast.

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The 1972 INTERCAL Compiler Revealed

June 2, 2025 by 19 Comments

Have you ever heard of INTERCAL? If you haven’t, don’t feel bad. This relatively obscure language dates back to 1972 with the goal of being difficult to read and write. It is the intellectual parent of systems like brainf**k and other bad languages. Now, you can read the INTERCAL-72 source code thanks to a found printout. It will help if you can read SPITBOL, another obscure language that is a compiled version of SNOBOL (which is like an old-fashioned non-Unix awk program).

How strange it INTERCAL? Well, one of the statements is PLEASE. If you don’t use it enough, you’ll offend the interpreter, who will then ignore your program. But if you use it too much, then you are a suck up and, therefore, your program will be ignored again. If you think GOTO is a bad idea, you’ll just hate COME FROM, although that was from a later version of INTERCAL.

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Mark Setrakian and Adam Savage investigate a massive prop hand

17 Year Old Hellboy II Prop Still Amazes

May 30, 2025 by 7 Comments

The AI effects we know these days were once preceded by CGI, and those were once preceded by true hand-built physical props. If that makes you think of Muppets, this video will change your mind. In a behind-the-scenes look with [Adam Savage], effects designer [Mark Setrakian] reveals the full animatronic glory of Mr. Wink’s mechanical fist from Hellboy II: The Golden Army (2008) – and this beast still flexes.

Most of this arm was actually made in 2003, when 3D printing was very different than what we think of today. Printed on a Stratasys Titan – think: large refrigerator-sized machine, expensive as sin – the parts were then hand-textured with a Dremel for that war-scarred, brutalist feel. This wasn’t just basic animatronics for set dressing. This was a fully actuated prop with servo-driven finger joints, a retractable chain weapon, and bevel-geared mechanisms that scream mechanical craftsmanship.

Each finger is individually designed. The chain reel: powered by a DeWalt drill motor and custom bevel gear assembly. Every department: sculptors, CAD modelers, machinists, contributed to this hybrid of analog and digital magic. Props like this are becoming unicorns.

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