Like many of us, [Tim]’s seen online videos of circuit sculptures containing illuminated LED filaments. Unlike most of us, however, he went a step further by using graph theory to design glowing structures made entirely of filaments.

The problem isn’t as straightforward as it might first appear: all the segments need to be illuminated, there should be as few powered junctions as possible, and to allow a single power supply voltage, all paths between powered junctions should have the same length. Ideally, all filaments would carry the same amount of current, but even if they don’t, the difference in brightness isn’t always noticeable. [Tim] found three ways to power these structures: direct current between fixed points, current supplied between alternating points so as to take different paths through the structure, and alternating current supplied between two fixed points (essentially, a glowing full-bridge rectifier).

To find workable structures, [Tim] represented circuits as directed graphs, with each junction being a vertex and each filament a directed edge, then developed filter criteria to find graphs corresponding to working circuits. In the case of power supplied from fixed points, the problem turned out to be equivalent to the edge-geodesic cover problem. Graphs that solve this problem are bipartite, which provided an effective filter criterion. The solutions this method found often had uneven brightness, so he also screened for circuits that could be decomposed into a set of paths that visit each edge exactly once – ensuring that each filament would receive the same current. He also found a set of conditions to identify circuits using rectifier-type alternating current driving, which you can see on the webpage he created to visualize the different possible structures.

We’ve seen some artistic illuminated circuit art before, some using LED filaments. This project doesn’t take exactly the same approach, but if you’re interested in more about graph theory and route planning, check out this article.

My colleague Lewin on the other side of the world has recently bought himself a new camera. It’s a very cute little thing, a Kodak Charmera, the latest badge-engineered device to carry the venerable photography company’s name. It’s a keyring camera, not much bigger than my thumb, and packing a few-megapixel sensor and a little fixed-focus camera module. They’re all the rage and thus always sold out, so when I saw something similar on AliExpress for just under a tenner I was curious enough to drop in an order. How bad could it be?

A Blatant-Knock-Off With Interesting Internals

My G6 Thumb Camera arrived a few days later, as straightforward a copy of a branded product as I have seen, and while it’s by any measure not a high quality camera, I am pleasantly surprised how bad it isn’t. I’ve received a three megapixel camera with image and movie quality that’s far better than that of the kids toy cameras I’ve played with before at a similar price, and that’s something I find amazing. This isn’t a review of a cheap camera, instead it’s an investigation of what goes into a camera like this one. How can they make a camera that’s almost useful, for under a tenner?

If I were setting out to make this camera, I would reach for a microcontroller and one of the variety of cheap all-in-one camera modules on the market. You can buy just that for a similar price, the so-called ESP32-cam module, which pairs the Tensilica version of the microcontroller with a parallel-interface camera module. You can do all manner of hacks with an ESP32-cam and I have too, but unlike my knock-off Kodak it’s not quite fast enough for usable video. Plus, it doesn’t come with a battery and screen.

The little thumb camera is easy enough to crack open, and doing so reveals a small PCB with as expected a camera module dangling from it on a flexible PCB. It’s got a lens with an M8 mount which technically makes it an interchangeable lens camera, but we doubt anyone’s going to change lenses on this thing. Undoing a couple of screws, the board comes out along with the battery, speaker, and display connection, and on the reverse is the SoC, and a Flash memory chip. It’s an HX-Tech HX3302B, a dedicated IC for small cameras which appears in so many of these devices, but one which is sadly one of those Chinese chips for which almost no info can be found online. Oddly some of the best info comes from a familiar source, Sprite_TM has done a little hacking here and discovered that it has an openRISC 1000 core and the firmware is usually accessible, but beyond that no handy data sheets are to be had.

Just Good Enough To Be A Camera-As-A-Module

My camera then can be software-hacked, but not easily. If that were all then we’d be at the end of it, and I’d have merely another trinket. But there’s another reason I bought this thing, and that’s because I wanted a hardware hackable camera, not a software one. I want to use a small sensor like this behind all manner of custom lenses and mirrors in projects featuring repurposed 1970s snapshot cameras, and while I can and have used Raspberry Pi cameras and those ESP32s to do the job, that introduces annoying things like software and power systems to the equation. This camera has the germ of a digital camera as a module; I can take away the M8 lens and surround to replace it with my own optics, and in an instant I have a digital camera of my own without the hassle. Suddenly a just-good-enough novelty camera becomes rather interesting.

So my knock-off novelty integrates a package I would struggle to replicate for the price, and holds the promise of many creative camera hacks to come. I’ll probably follow the path I have with Pi cameras of fitting an M12 macro lens, and rear-focusing on the focal plane of a full-frame film camera for retro digital fun.

In the ten days or so since the work for this article started, the G6 Thumb Camera has been removed from AliExpress in Europe. You can still find it by switching your country to somewhere far-flung, but given that as you can see from the photos above it really is a blatant knock-off of the Kodak product it is hardly surprising that some lawyers have probably made a call. The good news is though that for hacking it doesn’t matter what the case says. I’ll be looking out for the inevitable follow-up, a thumb camera that’s not such a knock-off but which packs the same internals, and if you’re enjoying camera hacking, I suggest you do too.