RF Noise Floor Concerns From Both Sides Of The Atlantic

July 20, 2017 by Jenny List 47 Comments

Our feed is full of stories about the RF noise floor today, and with good reason. The ARRL reports on the International Amateur Radio Union Region 1 president, [Don Beattie, G3BJ] warning that in densely populated parts of Europe there is a danger that parts of the RF spectrum have become so swamped with noise as to be rendered unusable, while on the other side of the Atlantic we have RadioWorld reporting on similar problems facing AM broadcasting in the USA.

At issue are the usual suspects, interference from poorly shielded or suppressed domestic electronic devices, VDSL broadband, power-over-Ethernet, solar and wind power systems, and a host of other RF-spewing electronics. The combined emissions from all these sources have raised the noise level at some frequencies to the point at which it conceals all but the strongest signals. Any radio amateur will tell you that a station in a rural location will be electrically much quieter than one in a city, it seems that this effect has now reached a crescendo.

In the RadioWorld article, the author [Tom F. King] and his collaborator [Jack Sellmeyer] detail a series of tests they performed on a selection of lighting products from a quality brand, bought at a local Home Depot store. They were gathering data for a submission to the FCC enquiry on the noise floor issue we reported on last year. What they found was unsurprising, significant emissions from all the products they tested. They make some stiff recommendations to the FCC and other bodies concerned with radio spectrum to get tough with offending devices, to stay on top of future developments, and for operators of AM stations to pursue sources of interference.

It could be that there is so much equipment contributing to the noise floor that this battle is lost, but it doesn’t have to be this way. Anyone who has had to prepare a product to pass a properly carried out EMC test will tell you that the requirements are stringent, and it is thus obvious that many manufacturers are shipping products unworthy of the certification they display. It is to be hoped that the authorities will begin to take it seriously before it becomes an order of magnitude worse.

Compliance label image, Moppet65535 [CC BY-SA 3.0].

Take Control Of Your Cheap Laser Cutter

July 19, 2017 by Jenny List 24 Comments

The relatively inexpensive K40 laser cutter/engraver machines from China have brought laser cutting to the masses, but they are not without their faults. Sure, they’re only powerful enough for the lightest cutting tasks, but on top of that, their bundled software is inflexible and disappointing. If your workshop or hackspace has one of these machines languishing in the corner, then the release of a new piece of software, K40 Whisperer from [Scorch], is an interesting and welcome development.

He tells us that the reverse engineering process required to understand the K40’s protocol was non-trivial, given that it does not use handy decimal numbers to issue commands. A spreadsheet was used to collate data packets and spot repeating patterns to analyse the inner workings. Feature-wise, the software reads SVG and DXF files, and can split SVGs by colour. It has a halftone algorithm for rendering grey scales, and cuts from the inside of each shape first to avoid pieces of work dropping out of the piece of material. Currently it works with the stock M2 Nano controller board and is available as a Windows download, though it can also be compiled for Linux distributions, or MacOS, and he is asking owners to test it with as many machines as possible to ensure compatibility with other boards.

He has posted a video of K40 Whisperer in action, which you can see below the break.

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Lethal LED Lantern Leaks Lotsa ‘Leccy

July 19, 2017 by Jenny List 40 Comments

When you take an item with you on a camping trip and it fails, you are not normally in a position to replace it immediately, thus you have the choice of fixing it there and then, or doing without it. When his LED camping lantern failed, [Mark Smith] was in the lucky position of camping at a friend’s compound equipped with all the tools, so of course he set about fixing it. What he found shocked him metaphorically, but anyone who handles it while it is charging can expect the more literal variation.

The lamp was an LED lantern with built-in mains and solar chargers for its Ni-Cd battery pack, and a USB charger circuit that provided a 5 volt output for charging phones and the like. The problem [Mark] discovered was that the mains charger circuit did not have any mains isolation, being a simple capacitive voltage dropper feeding a rectifier. These circuits are very common because they are extremely cheap, and are perfectly safe when concealed within insulated mains-powered products with no external connections. In the case of [Mark]’s lantern though the USB charging socket provided that external connection, and thus access to a potential 120 VAC shock for anyone touching it while charging.

Plainly this lamp doesn’t conform to any of the required safety standards for mains-powered equipment, and we’re guessing that its design might have come about by an existing safe lamp being manufactured with an upgrade in the form of the USB charger. The write-up gives it a full examination, and includes a modification to safely charge it from a wall-wart or similar safe power supply. Definitely one to watch out for!

If you were wondering what the fault was with Mark’s lamp, it was those cheap NiCd batteries failing. He replaced them, but there are plenty of techniques to rejuvenate old NiCds, both backyard, and refined.

Almost An Amiga For Not A Lot

July 18, 2017 by Jenny List 36 Comments

If you ask someone old enough to have been a computer user in the 16-bit era what machine they had, you’ll receive a variety of answers mentioning Commodore, Atari, Apple, or even PC brands. If your informant lay in the Commodore camp though, you’ll probably have an impassioned tale about their Amiga, its capabilities, and how it was a clearly superior platform whose potential was wasted. The Amiga was for a while one of the most capable commonly available computers, and became something of a cult within its own lifetime despite the truly dismal performance of the various companies that owned it. Today it retains one of the most active retro computer scenes, has an active software community, and even sees new hardware appearing.

For Amiga enthusiasts without the eye-watering sums required to secure one of the new Amiga-compatible machines with a PowerPC or similar at its heart, the only option to relive the glory beside finding an original machine is to run an emulator. [Marco Chiapetta] takes us through this process using a Raspberry Pi, and produces an Amiga that’s close enough to the real thing to satisfy most misty-eyed enthusiasts.

He starts with a cutesy Amiga-themed Raspberry Pi case that while it’s not essential for the build, makes an entirely appropriate statement about his new machine, We’re taken through the set-up of the Amibian emulator distro, then locating a set of Amiga ROMs. Fortunately that last step is easier than you might think, even without trawling for an illicit copy.

The result is an Amiga. OK, it’s not an Amiga, but without the classic Commodore logo is it any more not an Amiga than some of the other non-branded Amiga-compatible boards out there? Less talking, more classic gaming!

We’ve covered quite a few Amigas on these pages. Getting an A500 online was the subject of a recent post, and we brought you news of a new graphics card for the big-box Amiga’s Zorro slot.

The Acorn Archimedes At 30

July 17, 2017 by Jenny List 25 Comments

The trouble with being an incidental witness to the start of something that later becomes world-changing is that at the time you are rarely aware of what you are seeing. Take the Acorn Archimedes, the home computer for which the first ARM processor was developed, and which has just turned 30. If you were a British school pupil in 1987 who found a pair of the new machines alongside the row of BBC Micros in the school computer lab, for sure it was an exciting event, after all these were the machines everyone was talking about. But the possibility that their unique and innovative processor would go on to spawn a line of successors that would eventually power so much of the world three decades later was something that probably never occurred to spotty ’80s teens.

[Computerphile] takes a look at some of the first Archimedes machines in the video below the break. We get a little of the history and a description of the OS, plus a look at an early model still in its box and one of the last of the Archimedes line. Familiar to owners of this era of hardware is the moment when a pile of floppies is leafed through to find one that still works, then we’re shown the defining game of the platform, [David Braben]’s Lander, which became the commercial Zarch, and provided the template for his Virus and Virus 2000 games.

The Trojan Room Coffee Cam Archimedes, on display at the Cambridge University Computing Department.

We see the RiscOS operating system booting lightning-fast from ROM and still giving a good account of itself 20 years later even on a vintage Philips composite monitor. If you were that kid in 1987, you were in for a shock when you reached university and sat down in front of the early Windows versions, it would be quite a few years before mainstream computers matched your first GUI.

The Archimedes line and its successors continued to be available into the mid 1990s, but faded away along with Acorn through the decade. Even one being used to power the famous Trojan Room Coffee Cam couldn’t save it from extinction. We’re told they can still be found in the broadcast industry, and until fairly recently they powered much of the electronic signage on British railways, but other than that the original source of machines has gone. All is not lost though, because of course we all know about their ARM joint venture which continues to this day. If you would like to experience something close to an Archimedes you can do so with another computer from Cambridge, because RiscOS is available for the Raspberry Pi.

Sit back and enjoy the video, and if you were one of those kids in 1987, be proud that you sampled a little piece of the future before everyone else did.

Continue reading “The Acorn Archimedes At 30” →

Laser Exposing PCBs With A Blu-Ray Laser

July 14, 2017 by Jenny List 24 Comments

For those of us whose introduction to PCB making came decades ago and who share fond memories of permanent markers and crêpe paper sticky tape, the array of techniques available to PCB artists of today seem nothing short of magical. Toner transfer and peroxide etchant mixtures might seem run-of-the-mill to many readers, but even they are streets ahead of their predecessors from times past.

Photographic exposure of etch-resist coating has traditionally been performed with a UV lamp through a sheet of acetate film, but there is no reason why that should be the only way it can be performed. There have been plenty of projects using lasers or LEDs to draw a PCB design onto the coating as a raster, and a rather nice example from [Terje Io] using a Blu-Ray laser diode is the subject of the video below the break.

The diode is mounted on a gantry with a THK KR33 linear actuator that he tells us was unsuitable for his CNC mill due to backlash. This gives a claimed 1200 dpi resolution, over a 100 mm x 160 mm exposure area. Software is provided in a GitHub repository, taking a PNG image exported through a PDF printer. And since it’s got a UV laser, it can be used in a second pass to process UV-responsive soldermask film. ([Terje] cheats and uses a separate CNC mill to drill out the holes.) The result looks great.

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Hackaday Prize Entry: Open Narrowband RF Transceiver

July 14, 2017 by Jenny List 5 Comments

We have so many options when we wish to add wireless control to our devices, as technology has delivered a stream of inexpensive devices and breakout boards for our experimentation. A few dollars will secure you all your wireless needs, it seems almost whatever your chosen frequency or protocol. There is a problem with this boundless availability though, they can often be rather opaque and leave their users only with what their onboard firmware chooses to present.

The Open Narrowband RF Transceiver from [Samuel Žák] promises deliver something more useful to the experimenter: an RF transceiver for the 868 or 915MHz allocations with full control over all transmission parameters. Transmission characteristics such as frequency, bandwidth, and deviation can be adjusted, and the modulation and encoding schemes can also be brought under full control. Where a conventional module might simply offer on-off keying or frequency shift keying, this module can be programmed to deliver any modulation scheme its chipset is capable of. Spread-spectrum? No problem!

Onboard, the device uses the TI CC1120 transceiver chip, paired with the CC1190 front end and range extender. Overseeing it all is an ST Microelectronics STM32F051 microcontroller, which as you might expect is fully accessible to programmers. Interfaces are either USB, through an FTDI serial chip, or directly via a serial port.

There are a host of transceiver chips on the market which just beg to be exploited, so it is very good indeed to see a board like this one. It’s worth noting though that the CC1120 has a much wider frequency band than that of the CC1190, and with a different front end and PA circuitry, this could cover other allocations including some amateur bands.