Author: Lewin Day

3476 Articles

Light Following Robot Does It The Analog Way

January 28, 2026 by 12 Comments

If you wanted to build a robot that chased light, you might start thinking about Raspberry Pis, cameras, and off-the-shelf computer vision systems. However, it needn’t be so complex. [Ed] of [Death and the Penguin] demonstrates this ably with a simple robot that finds the light the old-fashioned way.

The build is not dissimilar from many line-following and line chasing robots that graced the pages of electronics magazines 50 years ago or more. The basic circuit relies on a pair of light-dependent resistors (LDR), which are wrapped in cardboard tubes to effectively make their response highly directional. An op-amp is used to compare the resistance of each LDR. It then crudely steers the robot towards the brighter light between turning one motor  hard on or the other, operating in a skid-steer style arrangement.

[Ed] then proceeded to improve the design further with the addition of a 555 timer IC. It’s set up to enable PWM-like control, allowing one motor to run at a lower speed than the other depending on the ratio between the light sensors. This provides much smoother steering than the hard-on, hard-off control of the simpler circuit. [Ed] notes that this is about the point where he would typically reach for a microcontroller if he hoped to add any additional sophistication.

In an era where microcontrollers seem to be the solution to everything, it’s nice to remember that sometimes you can complete a project without using a processor or any code at all. Video after the break.

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The Fancy Payment Cards Of Taiwan

January 28, 2026 by 22 Comments

If you’re an old-schooler, you might still go to the local bar and pay for a beer with cash. You could even try and pay with a cheque, though the pen-and-paper method has mostly fallen out of favor these days. But if you’re a little more modern, you might use a tap-to-pay feature on a credit or debit card.

In Taiwan, though, there’s another unique way to pay. The island nation has a whole ecosystem of bespoke payment cards, and you can even get one that looks like a floppy disk!

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How HP Calculators Communicate Over Infrared

January 27, 2026 by 10 Comments

For most people, calculators are cheap and simple devices used for little more than addition and the odd multiplication job. However, when you get into scientific and graphical calculators, the feature sets get a lot more interesting. For example, [Ready? Z80] has this excellent explainer on how HP’s older calculators handle infrared communications.

The video focuses on the HP 27S Scientific Calculator, which [Ready? Z80] found in an op-shop for just $5. Introduced in 1988, the HP-27S had the ability to dump screen data over an infrared link to a thermal printer to produce paper records of mundane high-school calculations or important engineering math. In the video, [Ready? Z80] explains the communication method with the aid of Hewlett-Packard’s own journal publication from October 1987, which lays out of the details of “the REDEYE Protocol.” Edgy stuff. It’s pretty straightforward to understand, with the calculator sending out bursts of data in six to eight pulses at a time, modulated onto a 32.768KHz square wave as is the norm. [Ready? Z80] then goes a step further, whipping up custom hardware to receive the signal and display the resulting data on a serial terminal. This is achieved with a TEC-1G single-board computer, based on the Z80 CPU, because that’s how [Ready? Z80] does things.

We’ve seen other great stuff from this channel before, too. For example, if you’ve ever wanted to multitask on the Z80, it’s entirely possible with the right techniques. Video after the break.

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Smoothie Bikes Turned Into Game Controllers

January 27, 2026 by 9 Comments

Smoothie bikes are a great way to make a nutritious beverage while getting a workout at the same time. [Tony Goacher] was approached by a local college, though, which had a problem with this technology. Namely, that students were using them and leaving them filthy. They posed a simple question—could these bikes become something else?

[Tony’s] solution was simple—the bikes would be turned into game controllers. This was easily achieved by fitting a bi-color disc into the blender assembly. As the wheel on the bike turns, it spins up the blender, with the disc inside. An ESP32 microcontroller paired with a light sensor is then able to count pulses as the disc spins, getting a readout of the blender’s current RPM. Working backwards, this can then be calculated out into the bike’s simulated road speed and used to play a basic game on an attached Raspberry Pi. Notably, the rig is setup such that the Raspberry Pi and one bike connect to an access point hosted by the other bike.  This is helpful, because it means neither bike has too many dangling cables that could get caught up in a wheel or chain.

We’ve seen many amusing game peripherals over the years, from salad spinners to turntables. Video after the break.

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Regrowing Teeth Might Not Be Science Fiction Anymore

January 27, 2026 by 32 Comments

The human body is remarkably good at handling repairs. Cut the skin, and the blood will clot over the wound and the healing process begins. Break a bone, and the body will knit it back together as long as you keep it still enough. But teeth? Our adult teeth get damaged all the time, and yet the body has almost no way to repair them at all. Get a bad enough cavity or knock one out, and it’s game over. There’s nothing to be done but replace it.

Finding a way to repair teeth without invasive procedures has long been a holy grail for dental science. A new treatment being developed in Japan could help replace missing teeth in the near future.

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Running DOOM On Earbuds

January 27, 2026 by 4 Comments

In 1993, DOOM was a great game to play if you had a 486 with a VGA monitor and nothing to do all weekend. In 2026, you can play it on a set of earbuds instead, if for some reason that’s something you’ve always dreamed of doing.

The project comes to us from [Arin Sarkisian], who figured out that the Pinebuds Pro had enough processing power to run one of the seminal FPS games from the 1990s. Inside these earbuds is a Cortex-M4F, which is set to run at 100 MHz. [Arin] figured out it could easily be cranked up to 300 MHz with low power mode switched off, which would come in handy for one main reason. See, the earbuds might be able to run the DOOM engine, but they don’t have a display.

Thus, [Arin] figured the easiest way to get the video data out would be via the Cortex-M4F’s serial UART running at 2.4 mbps. Running the game at a resolution of 320 x 200 at 3 frames per second would consume this entire bandwidth. However, all those extra clock cycles allow running an MJPEG compression algorithm that allow spitting out up to 18 frames per second. Much better!

All that was left to do was to figure out a control scheme. To that end, a web server is set up off-board that passes key presses to the buds and accepts and displays the MJPEG stream to the player. If you’re so inclined you can even play the game yourself on the project website, though you might just have to get in a queue. In the meantime, you can watch the Twitch stream of whoever else is playing at the time.

Files are on GitHub—both the earbud firmware and the web interface used to play the game. It was perhaps only a matter of time until we saw DOOM on earbuds; no surprise given that we’ve already seen it played on everything from receipt printers to cookware. No matter how cliche, we’re going to keep publishing interesting DOOM ports—so keep them coming to the tipsline.

Thanks to [alialiali] for the tip!

Zombie Netscape Won’t Die

January 27, 2026 by 25 Comments

The very concept of the web browser began with a humble piece of software called NCSA Mosaic, all the way back in 1993. It was soon eclipsed by Netscape Navigator, and later Internet Explorer, which became the titans of the 1990s browser market. In turn, they too would falter. Navigator’s dying corpse ended up feeding what would become Mozilla Firefox, and Internet Explorer later morphed into the unexceptional browser known as Edge.

Few of us have had any reason to think about Netscape Navigator since its demise in 2008. And yet, the name lingers on. A zombie from a forgotten age, risen again to haunt us today.

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