The Isetta TTL Computer Makes Some Noise

October 24, 2025 by Jenny List 5 Comments

Our Hackaday colleague [Bil Herd] is known for being the mind behind the Commodore 128, a machine which famously had both a 6502 and a Z80 processor on board. The idea of a machine which could do the job of both those processors in hardware while containing neither would have blown the mind of any 1980s computer enthusiast, yet that’s exactly what [Roelh]’s Isetta TTL computer does. It’s an extremely clever design whose targeted microcode allows the processor-swap trick, and since he’s brought it from prototype to production and has it running SymbOS since we last saw it, it’s time we gave it another look.

A diagram showing chip placement on the Isetta PCB. — All the functions on what is a surprisingly compact board.

The video below the break shows the machine in action, with the Windows 95-like SymbOS GUI running a series of sound tests in the emulated AY-3-8910 sound generator, as well as a Lemmings-like game. It also runs Sinclair ZX Spectrum software, giving it access to a huge library.

We were lucky enough to see some of this in person when we encountered it for a second time on our travels during the summer — and it’s just as impressive in the real as it looks in the video. The feeling really hits you of how this would have blown away anything on the 8-bit market in 1985, made more impressive by the silicon in use being not too far from what was available at the time.

We’re told you can now buy one for yourself as a kit, and we’re looking forward to seeing it generate an ecosystem. We’re particularly curious as to whether that retargetable microcode could allow it to support other archetctures of the day.

Our original coverage can be read here, and we’ve also touched upon SymbOS.

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Tommy Flowers: How An Engineer Won The War

October 24, 2025 by Jenny List 26 Comments

Back in 2016, we took you to a collection of slightly dilapidated prefabricated huts in the English Home Counties, and showed you a computer. The place was the National Museum of Computing, next to the famous Bletchley Park codebreaking museum, and the machine was their reconstruction of Colossus, the world’s first fully electronic digital computer. Its designer was a telephone engineer named Tommy Flowers, and the Guardian has a piece detailing his efforts in its creation.

The front of the museum's Colossus MkII. — TNMOC’s Colossus MkII.

It’s a piece written for a non-technical audience so you’ll have to forgive it glossing over some of the more interesting details, but nevertheless it sets out to right a long-held myth that the machine was instead the work of the mathematician Alan Turing. Flowers led the research department at the British Post Office, who ran the country’s telephone system, and was instrumental both in proposing the use of electronic switches in computing, and in producing a working machine. The connection is obvious when you see Colossus, as its racks are the same as those used in British telephone exchanges of the era.

All in all, the article makes for an interesting read for anyone with an interest in technology. You can take a look at Colossus as we saw it in 2016 here, and if your interest extends to the only glimpse the British public had of the technology behind it in the 1950s, we’ve also taken a look at another Tommy Flowers creation, ERNIE, the UK Premium Bond computer.

British Train Departures As They Should Be Viewed

October 21, 2025 by Jenny List 33 Comments

The first generation of real-time train information screens for British railways came in the form of suspended color CRTs in familiar rounded fiberglass housings. They were a ubiquitous sight across the network for years, until of course suddenly, they weren’t. Can they be brought back? [Heliomass] has come about as close as it’s possible to be, with a modern emulation that runs from live data feeds.

The screens were recognizably using the same graphics standards as Teletext, and thus it was no surprise back in the day to see from time to time an Acorn boot screen in a railway station.

We remember some debate at the time as to whether they were running Archimedes of BBC Micro hardware behind the scenes, though it seems likely it might have been the industrial BBC Micro derivative.

The modern recreation uses an emulated BBC Micro for the signage, with a serial connection to a server component running in Python on more modern hardware. This handles grabbing the data and sending it to the Beeb for display. The result is an unexpected bit of nostalgia for anyone who spent the 1980s or ’90s in south east England.

Broken Phone To Cinema Camera With A Lens Upgrade

October 18, 2025 by Jenny List 8 Comments

The advent of the mobile phone camera has caused a revolution in film making over the last couple of decades, lowering the barrier to entry significantly, and as the cameras have improved, delivering near-professional-grade quality in some cases. Mobile phone manufacturers hire film makers to promote their new flagship models and the results are very impressive, but there is still a limitation when it comes to the lenses. [Evan Monsma] has broken through that barrier, modifying an iPhone to take C-mount cinema lenses.

It’s likely many of us have one or two broken mobile phones around, and even if they aren’t flagship models they’ll still have surprisingly good camera sensors. This one is an iPhone that’s seen better days, with a severely cracked glass back and a dislodged lens cover on one of its cameras. Removing the back and the lens cover reveals the sensor. The video below the break has a lot of woodwork and filing away of the phone, as he modifies a C-to-CS ring to serve as a C-mount. In reality the flange distance makes it a CS mount so his C-mount lenses need an adapter, but as anyone who’s used a Raspberry Pi camera will tell you, that’s no hardship.

The final camera has a thick plywood back with a tripod mount installed, the other two cameras work with their Apple lenses, and the C-mount gives great results with a cinema lens. We’re concerned that the Super Glue he uses to fix it all together might not hold up to the weight of bigger lenses, but we’re here for this project and we love it.

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2025 Component Abuse Challenge: Boosting Voltage With Just A Wire

October 17, 2025 by Jenny List 13 Comments

Switching power supplies are familiar to Hackaday readers, whether they have a fairly conventional transformer, are a buck, a boost, or a flyback design. There’s nearly always an inductor involved, whose rapid change in magnetic flux is harnessed to do voltage magic. [Craig D] has made a switching voltage booster that doesn’t use an inductor, instead it’s using a length of conductor, and no, it’s not using the inductance of that conductor as a store of magnetic flux.

Instead it’s making clever use of reflected short pulses in a transmission line for its operation. Electronics students learn all about this in an experiment in which they fire pulses down a length of coax cable and observe their reflections on an oscilloscope, and his circuit is very similar but with careful selection of pulse timing. The idea is that instead of reflected pulses canceling out, they arrive back at the start of the conductor just in time to meet a pulse transition. This causes them to add rather than subtract, and the resulting higher voltage pulse sets off down the conductor again to repeat the process. We can understand the description, but this is evidently one to sit down at the bench and experiment with to fully get to grips with.

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2025 Component Abuse Challenge: An LED As A Light Dependent Capacitor

October 16, 2025 by Jenny List 15 Comments

The function of an LED is to emit light when the device is forward biased within its operating range, and it’s known by most people that an LED can also operate as a photodiode. Perhaps some readers are also aware that a reverse biased LED also has a significant capacitance, to the extent that they can be used in some RF circuits in the place of a varicap diode. But how do those two unintentional properties of an LED collide? As it turns out, an LED can also behave as a light dependent capacitor. [Bornach] has done just that, and created a light dependent sawtooth oscillator.

The idea is simple enough, there is a capacitance between the two sides of the depletion zone in a reverse biased diode, and since an LED is designed such that its junction is exposed to the external light, any photons which hit it will change the charge on the junction. Since the size of the depletion zone and thus the capacitance is dependent on the voltage and thus the charge, incoming light can thus change the capacitance.

The circuit is a straightforward enough sawtooth oscillator using an op-amp with a diode in its feedback loop, but where we might expect to find a capacitor to ground on the input, we find our reverse biased LED. The video below the break shows it in operation, and it certainly works. There’s an interesting point here in that and LED in this mode is suggested as an alternative to a cadmium sulphide LDR, and it’s certainly quicker responding. We feel duty bound to remind readers that using the LED as a photodiode instead is likely to be a bit simpler.

This project is part of the Hackaday Component Abuse Challenge, in which competitors take humble parts and push them into applications they were never intended for. You still have time to submit your own work, so give it a go!

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Keep That Engine Running, With A Gassifier

October 15, 2025 by Jenny List 53 Comments

Every now and then in histories of the 20th’s century’s earlier years, you will see pictures of cars and commercial vehicles equipped with bulky drums, contraptions to make their fuel from waste wood. These are portable gas generators known as gasifiers, and to show how they work there’s [Greenhill Forge] with a build video.

A gasifier on a vintage tractor. Per Larssons Museum, CC BY 2.5.

When you burn a piece of wood, you expect to see flame. But what you are looking at in that flame are the gaseous products of the wood breaking down under the heat of combustion. The gasifier carefully regulates a burn to avoid that final flame, with the flammable gasses instead being drawn off for use as fuel.

The chemistry is straightforward enough, with exothermic combustion producing heat, water vapour, and carbon dioxide, before a further endothermic reduction stage produces carbon monoxide and hydrogen. He’s running his system from charcoal which is close to pure carbon presumably to avoid dealing with tar, and at this stage he’s not adding any steam, so we’re a little mystified as to where the hydrogen comes from unless there is enough water vapour in the air.

His retort is fabricated from sheets steel, and is followed by a cyclone and a filter drum to remove particulates from the gas. It relies on a forced air draft from a fan or a small internal combustion engine, and we’re surprised both how quickly it ignites and how relatively low a temperature the output gas settles at. The engine runs with a surprisingly simple gas mixer in place of a carburetor, and seems to be quite smooth in operation.

This is one of those devices that has fascinated us for a long time, and we’re grateful for the chance to see it up close. The video is below the break, and we’re promised a series of follow-ups as the design is refined.

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