A Few New Car Owners Will Join The 48V Future

December 1, 2023 by Jenny List 135 Comments

Leaving aside all the annoying hype surrounding Tesla’s Cybertruck, there’s a little technical detail which might be of more interest to readers than the automotive behemoth itself. It’s one of very few vehicles on the road to eschew 12 volt electrics for not 24 volt, but 48 volt. This has been one of those automotive innovations promised as just around the corner for many years, and it seems finally we’ll see it in practice.

The reason that there’s nothing new in the prospect of moving on from 12 volt electrics has been brewing for decades now. A typical car has plenty of motorized gadgets from seat adjusters to sunroofs, as well as at least one heated windscreen or other surface. These devices take a lot of power, and at the lower voltage require significant current to operate. The 48 volt system will require much less in the way of copper to get the power where it’s needed, so the surprise is that we’ve not yet seen it in run-of-the-mill vehicles from the likes of Ford or Volkswagen.

What we’re guessing is that other manufacturers will be watching from the sidelines as to whether 48 volt electrics cause any problems for the Tesla, and it’s not impossible we could see it becoming the new hotness. There are many choice words we could say relating to the hype around Tesla and its supposed level of innovation, but it could be that this time they’ve really been first with something the whole industry will go for. If so we should rejoice, because it’s likely to push down the prices of 48 volt lithium-ion packs.

Header image: Mliu92, CC BY-SA 3.0.

The Minimum Required For A Film Camera

November 30, 2023 by Jenny List 13 Comments

Film cameras can be complex and exquisitely-crafted masterpieces of analogue technology. But at their very simplest they need be little more than a light-proof box with a piece of film at the back of it, and some kind of lens or pinhole with a shutter. [ChickenCrimpy] adds the most basic of 35 mm cartridge to create what he calls the Minimum Viable Camera. It’s a half-frame 35 mm pinhole film camera with the simplest possible construction.

It can be built from almost any flat light-proof 3 mm thick stock, though something that you can run through a laser cutter is probably ideal. Once snapped together to make to box-like structure, tape is added along the joins for light-proofing. The film is reeled from a full 35 mm cartridge to an empty one, and cranked back frame-by-frame by means of a wooden key that engages with the spindle.

There’s no lens, instead this is a pinhole camera, and the shutter is a piece of the stock held on the front of the camera with bolts and butterfly nuts. Taking a photo is as simple as pointing the device at the subject and lifting the shutter away for a few seconds. There’s a video overview for the project which we’ve placed below the break.

It’s true that this camera needs a moment in the darkroom to load, but we like its extreme simplicity and the ethereal and grainy pictures it produces. If you fancy an introduction to 35 mm photography you could definitely do worse.

Continue reading “The Minimum Required For A Film Camera” →

Noise Cancelling Isn’t As Easy As You’d Think

November 28, 2023 by Jenny List 14 Comments

On the face of it, producing a set of noise cancelling headphones should be a relatively straightforward project. But as [Pete Lewis] found out, things are not always as they seem. The result is a deep dive into microphone specifications, through which most of us could probably learn something.

Noise cancelling headphones have a set of microphones which provide anti-phase noise through an amplifier to the ‘phones, thus in theory cancelling out the external noise. Since [Pete] is a musician this pair would have to be capable of operating at high noise levels, so he checked the spec for his microphone and with an acoustic overload point at 124 dB for a 115 environment he was ready to go.

Unfortunately these ‘phones showed distortion, which brings us back to the acoustic overload point. This is the sound level at which the microphone has 10% distortion, which is a very high figure, and certainly meant there was enough distortion to be audible at the lower level. After a search for a higher spec microphone and a move to a digital codec-based solution with an ESP32 he eventually cracks it though, leading to an inexpensive set of noise cancelling headphones for high-noise environments.

If distortion interests you, it’s a subject we’ve visited in the past.

Header image: fir0002, GFDL 1.2.

A Flasher Mac, 25 Years Later

November 28, 2023 by Jenny List 6 Comments

Apple Macintosh computers of the 1990s came with a system ROM containing an Open Firmware implementation and the Mac Toolbox required to start the operating system. In many cases this was on a SIMM-like daughter board, and it would have been a true ROM that was unable to be reprogrammed. This is not the end of the story though, and [Doug Brown] set out on the trail of a Flash-based ROM module allowing the firmware on these machines to be updated.

The trail was warm thanks to an Apple developer utility found on a secondhand Mac prototype, allowing ROM flashing. A little disassembly allowed a list of valid IDs to be made, and this info coupled with a bit of reverse engineering from online photos of a real Apple Flash ROM from the ’90s allowed a new board to be created with four Am28F020 chips. He can now flash at will, with such oddities as running ROMs from different machines with the “wrong” startup chime. It’s an interesting little piece of 1990s Mac trivia, settled.

This isn’t the first time we’ve peered at Apple ROMs, indeed some of the older ones had plenty of Easter eggs hidden within.

A 48 Volt Battery Pack With Carefully Balanced Cells

November 28, 2023 by Jenny List 60 Comments

Many readers will have at some time or another built their own lithium-ion battery packs, whether they are using tiny cells or the huge ones found in automotive packs. A popular choice it to salvage ubiquitous 18650 cylindrical cells, as [limpkin] has with this 48 volt pack. It’s based around an off-the-shelf kit aimed at the e-bike market, but it’s much more than a simple assembly job.

Faced with a hundred salvaged cells of unknown provenance, the first thing to do was ensure that they were all balanced and showed the same voltage. Some might do this the inefficient way by hooking each one up to a charger and a programmable load, but in this case a much more radical route was taken. A huge PCB was designed with sockets for all hundred cells, connected in parallel through individual series resistors. This allowed them to balance to a common voltage before being discharged to a safe voltage for assembly. Their individual ESRs were the measured, and the best performing examples were then spot-welded into the final 13s-6p final pack.

We all use lithium-ion batteries, but how many of us know how they work?

A Tube Guitar Amp For A Modest Budget

November 27, 2023 by Jenny List 17 Comments

There’s a mystique among both audiophiles and musicians about vacuum technology, thus having a tube amp still carries a bit of a cachet. New ones can be bought for eye-watering prices and old ones can be had for the same price with the added frisson of unreliability. Happily it’s surprisingly straightforward to build your own, as [_electroidiot] shows us with a fairly inexpensive build.

The design is inspired by the guitar amps of the 1950s and 1960s so it’s not for audiophiles. The circuit is a pretty conventional single-ended one with a two stage double triode preamp and a single power output tube. The transformers are usually the difficult part of a build like this one, and here instead of resorting to using a mains transformer for audio they come from a defunct 1960s Phillips radio. We especially like the old-school construction technique with a folded aluminium chassis and liberal use of tag strips on which to build the circuits.

The result is something that would have been in no way out of place in the 1960s, and proves that tube circuitry isn’t beyond the constructor in 2023. If it’s whetted your appetite for more, we can help you there.

Could North Korea’s New Satellite Have Spied On Guam So Easily?

November 27, 2023 by Jenny List 29 Comments

Earlier this week, another nation joined the still relatively exclusive club of those which possess a satellite launch capability. North Korea launched their Malligyong-1 spy satellite, and though it has naturally inflamed the complex web of political and military tensions surrounding the Korean peninsula, it still represents something of a technical achievement for the isolated Communist state. The official North Korean news coverage gleefully reported with much Cold War style rhetoric, that Kim Jong-Un had visited the launch control centre the next day and viewed intelligence photographs of an American base in Guam. Could the satellite have delivered in such a short time? [SatTrackCam Leiden] has an interesting analysis. Continue reading “Could North Korea’s New Satellite Have Spied On Guam So Easily?” →