Disposable Camera Viewfinder Becomes 3D Printed Lens

December 24, 2025 by No comments

Disposable cameras are a fun way to get into classical photography. However, they can also be a valuable source of interesting parts that can be put to other uses. For example, as [Billt] demonstrates, their viewfinders can be repurposed into a rather interesting lens for more serious cameras.

[Billt] was lucky enough to score a grabbag of used disposable cameras from a local film lab, and tore them down for parts. He was particularly interested in the viewfinders, since Kodak equipped its disposable cameras with actual plastic lenses for this very purpose.

[Billt] wanted to see what these lenses would do when thrown on the front of a proper digital camera, and set about designing a mount for that purpose. The 3D printed part was designed to mount one of the viewfinder lens assemblies on the front of any Sony E-mount camera. In a rather nifty trick, [Billt] realized the lens assembly could be installed in the adapter by pausing mid-way through the 3D print to drop it in. The only unfortunate thing? The lenses didn’t really work, and all the camera could see was a haze of unfocused light.

With the aid of some cardboard experiments, [Billt] decided to make some changes. The front element of the viewfinder was dumped, with the rear element being used solo instead. This was fitted to the adapter on a simple slide mechanism so that focus could be reliably adjusted. With these changes, the lens came good, and provided some really interesting shots. It’s quite a cropped lens and it can achieve a very close focus distance, as little as 1 inch in testing. It’s quite sharp in the center of the image, while softly blurring out towards the edges—something that sounds very familiar if you’ve used one of these disposable cameras in the wild.

Sometimes it’s fun to grab a random piece of junk to see if you can turn it into something good. Video after the break.

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DIY E-Reader Folds Open Like A Book

December 24, 2025 by 7 Comments

There are plenty of lovely e-readers out on the market that come with an nice big e-paper display. There aren’t nearly as many that come with two. [Martin den Hoed] developed the Diptyx e-reader with such a design in order to better replicate the paper books of old. 

The build is based around the ESP32-S3, a powerful microcontroller which comes with the benefit of having WiFi connectivity baked in. It’s hooked up to a pair of 648×480 e-paper displays, which are installed in a fold-open housing to create the impression that one is reading a traditional book. The displays themselves are driven with custom look-up tables to allow for low-latency updates when turning pages. The firmware of the device is inspired by the epub reader from [Atomic14], and can handle different fonts and line spacing without issue. Power is from a pair of 1,500 mAh lithium-polymer cells, which should keep the device running for a good long time, and they can be charged over USB-C like any  modern gadget.

You can follow along with the project on the official website, or check it out on Crowd Supply if you’re so inclined. The project is intended to be open source, with files to be released once the design is finalized for an initial production run.

We’ve seen some great DIY e-reader builds over the years, and we’re loving the development we’re seeing in the writer deck space, too. If you’re whipping up something fun in this vein, be sure to let us know on the tipsline!

Roll Your Own Hall Effect Sensor

December 24, 2025 by 6 Comments

If you read about Hall effect sensors — the usual way to detect and measure magnetic fields these days — it sounds deceptively simple. There’s a metal plate with current flowing across it in one direction, and sensors at right angles to the current flow. Can it really be that simple? According to a recent article in Elektor, [Burkhard Kainka] says yes.

The circuit uses a dual op amp with very high gain, which is necessary because the Hall voltage with 1 A through a 35 micron copper layer (the thickness on 1 oz copper boards) is on the order of 1.5 microvolts per Tesla. Of course, when dealing with tiny voltages like that, noise can be a problem, and you’ll need to zero the amplifier circuit before each use.

The metal surface? A piece of blank PCB. Copper isn’t the best material for a Hall sensor, but it is readily available, and it does work. Of course, moving the magnet can cause changes, and the whole thing is temperature sensitive. You wouldn’t want to use this setup for a precision measurement. But for an experimental look at the Hall effect, it is a great project.

Today, these sensors usually come in a package. If you want to know more about the Hall effect, including who Edwin Hall was, we can help with that, too.

Silicon-Based MEMS Resonators Offer Accuracy In Little Space

December 24, 2025 by 1 Comment

Currently quartz crystal-based oscillators are among the most common type of clock source in electronics, providing a reasonably accurate source in a cheap and small package. Unfortunately for high accuracy applications, atomic clocks aren’t quite compact enough to fit into the typical quartz-based temperature-compensated crystal oscillators (TCXOs) and even quartz-based solutions are rather large. The focus therefore has been on developing doped silicon MEMS solutions that can provide a similar low-drift solution as the best compensated quartz crystal oscillators, with the IEEE Spectrum magazine recently covering one such solution.

Part of the DARPA H6 program, [Everestus Ezike] et al. developed a solution that was stable to ±25 parts per billion (ppb) over the course of eight hours. This can be contrasted with a commercially available TCXO like the Microchip MX-503, which boasts a frequency stability of ±30 ppb.

Higher accuracy is achievable by swapping the TCXO for an oven-controlled crystal oscillator (OCXO), with the internal temperature of the oscillator not compensated for, but rather controlled with an active heater. There are many existing OCXOs that offer down to sub-1 ppb stability, albeit in quite a big package, such as the OX-171 with a sizable 28×38 mm footprint.

With a MEMS silicon-based oscillator in OXCO configuration [Yutao Xu] et al. were able to achieve a frequency stability of ±14 ppb, which puts it pretty close to the better quartz-based oscillators, yet within a fraction of the space. As these devices mature, we may see them eventually compete with even the traditional OCXO offerings, though the hyperbolic premise of the IEEE Spectrum article of them competing with atomic clocks should be taken with at least a few kilograms of salt.

Thanks to [anfractuosity] for the tip.

Nixie Tube Dashboard Is Period-Appropriate Hack To Vintage Volvo

December 24, 2025 by 8 Comments

There’s no accounting for taste, but it’s hard to argue with The Autopian when they declare that this Nixie tube dash by [David Forbes] is “the coolest speedometer of all time” — well, except to quibble that it’s also the coolest tachometer, temperature gauge, oil pressure indicator, and voltmeter. Yeah, the whole instrument cluster is on [David]’s Volvo PV544 is nixified, and we’re here for it.

He’s using a mixture of tubes here– the big ones in the middle are the speedo and tachometer, while the ovals on either side handle the rest. There’s a microcontroller on the front of the firewall that acts a bit like a modern engine control unit (ECU) — at least for the gauges; it sounds like the Volvo’s engine is stock, and that means carbureted for a car of that vintage.

The idea that this hack could have been done back in the 50s when the car was new just tickles us pink. Though you’d have probably needed enough valves to fill up the boot, as our British friends would say. Translate that to “enough vacuum tubes to fill the trunk” if you’re in one of the rebellious colonies.

We’ve featured [David]’s projects previously, in the form of his wearable video coat. But his best known work is arguably the Nixie Watch, famously the timepiece of choice for Steve Wozniak.

Thanks to [JohnU] for the tip!

All images by Griffin Riley via The Autopian

Exploring Modern SID Chip Substitutes

December 23, 2025 by 8 Comments
The SIDKick Pico installed on a breadboard. (Credit: Ben Eater)
The SIDKick Pico installed on a breadboard. (Credit: Ben Eater)

Despite the Commodore 64 having been out of production for probably longer than many Hackaday readers have been alive, its SID audio chip remains a very popular subject of both retrocomputing and modern projects. Consequently a range of substitutes have been developed over the decades, all of which seek to produce the audio quality of one or more variants of the SID. This raises the question of which of these to pick when at first glance they seem so similar. Fret not, for [Ben Eater] did an entire video on comparing some modern SID substitutes and his thoughts on them.

First is the SIDKick Pico, which as the name suggests uses a Raspberry Pi Pico board for its Cortex-M0+ MCU. This contrasts with the other option featured in the video, in the form of the STM32F410-based ARMSID.

While the SIDKick Pico looks good on paper, it comes with a number of different configurations, some with an additional DAC, which can be confusing. Because of how it is stacked together with the custom PCB on which the Pi Pico is mounted, it’s also pretty wide and tall, likely leading to fitment issues. It also doesn’t work as a drop-in solution by default, requiring soldering to use the SID’s normal output pins. Unfortunately this led to intense distortion in [Ben]’s testing leading him to give up on this.

Meanwhile the ARMSID is about as boring as drop-in replacements get. After [Ben] got the ARMSID out of its packaging, noted that it is sized basically identical to the original SID and inserted it into the breadboard, it then proceeded to fire right up with zero issues.

It’s clear that the SIDKick Pico comes with a lot of features and such, making it great for tinkering. However, if all you want is a SID-shaped IC that sounds like a genuine SID chip, then the ARMSID is a very solid choice.

Thanks to [Mark Stevens] for the tip.

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Breathe Easy While Printing With This VOC Calculator

December 23, 2025 by 1 Comment

We love 3D printing here, but we also love clean air, which produces a certain tension. There’s no way around the fact that printing produces various volatile organic compounds (VOCs), and that we don’t want to breathe those any more than necessary. Which VOCs, and how much? Well, [Jere Saikkonen] has created a handy-dandy calculator to help you guesstimate your exposure, or size your ventilation system, at least for FDM printing.

The emissions of most common FDM filaments are well-known by this point, so [Jere] was able to go through the literature and pull out values for different VOCs of concern like styrene and formaldehyde for ABS, PLA, Nylon, HIPS and PVA. We’re a bit disappointed not to see PETG or TPU on there, as those are common hobbyist materials, but this is still a great resource.

If you don’t like the numbers the calculator is spitting out, you can play with the air exchange rate setting to find out just how much extra ventilation you need. The one limitation here is that this assumes equilibrium conditions, which won’t be met save for very large prints. That’s arguably a good thing, since it errs on the side of over- rather than underestimating your exposure.

If you want to ground-truth this calculator, we’ve featured VOC-sensing projects before. If you’re convinced the solution to pollution is dilution, check out some ventilated enclosures. If you don’t want to share chemistry with the neighborhood, perhaps filtration is in order. 

Thanks to [Jere] for the tip!