Author: Jenny List

3429 Articles

A Capacitive Soil Sensor Hack For Lower Voltage Supplies

July 27, 2019 by 24 Comments

A frequent beginner project involves measuring soil moisture levels by measuring its resistance with a couple of electrodes. These electrodes are available ready-made as PCBs, but suffer badly from corrosion. Happily there is a solution in the form of capacitive sensor probes, and it is these that [Electrobob] is incorporating in to a home automation system. Unfortunately the commercial capacitive probes are designed to run from a 3.3 V supply and [Bob]’s project is using a pair of AA cells, so a quick hack was needed to enable them to be run from the lower voltage.

The explanation of the probe’s operation is an interesting part of the write-up, unexpectedly it uses a 555 configured as an astable oscillator. This feeds an RC low pass filter of which the capacitor is formed by the soil probe, which in turn feeds a rectifier to create a DC output. This can be measured to gain a reading of the soil moisture level.

The probe is fitted with a 3.3 V LDO regulator, which is simply bypassed. Measurements show its output to be linear, so if the supply voltage is also measured an accurate reading can be gleaned. These probes are still a slightly unknown quantity to many who might find a use for them, so it’s extremely useful to be given this insight into them.

Retrotechtacular: The Floppy Disk Orphaned By Linux

July 26, 2019 by 105 Comments

About a week ago, Linus Torvalds made a software commit which has an air about it of the end of an era. The code in question contains a few patches to the driver for native floppy disc controllers. What makes it worthy of note is that he remarks that the floppy driver is now orphaned. Its maintainer no longer has working floppy hardware upon which to test the software, and Linus remarks that “I think the driver can be considered pretty much dead from an actual hardware standpoint“, though he does point out that active support remains for USB floppy drives.

It’s a very reasonable view to have arrived at because outside the realm of retrocomputing the physical rather than virtual floppy disk has all but disappeared. It’s well over a decade since they ceased to be fitted to desktop and laptop computers, and where once they were a staple of any office they now exist only in the “save” icon on your wordprocessor. The floppy is dead, and has been for a long time.

The save icon in LibreOffice and other desktop software is probably the last place the floppy exerts a hold over us.
The save icon in LibreOffice and other desktop software is probably the last place the floppy exerts a hold over us.

Still, Linus’ quiet announcement comes as a minor jolt to anyone of A Certain Age for whom the floppy disk and the computer were once inseparable. When your digital life resided not in your phone or on the cloud but in a plastic box of floppies, those disks meant something. There was a social impact to the floppy as well as a technological one, they were a physical token that could contain your treasured ephemeral possessions, a modern-day keepsake locket for the digital age. We may have stopped using them over a decade ago, but somehow they are still a part of our computing DNA.

So while for some of you the Retrotechtacular series is about rare and unusual technology from years past, it’s time to take a look at something ubiquitous that we all think we know. Where did the floppy disk come from, where is it still with us, and aside from that save icon what legacies has it bestowed upon us?

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HDMI From Your Arduino

July 26, 2019 by 29 Comments

Creating a video signal from a computer, a job that once required significant extra hardware, is now a done deal with a typical modern microcontroller. We’ve shown you more NTSC, PAL, and VGA projects than you can shake a stick at over the years. Creating an HDMI video signal however is not so straightforward. It’s not a loosely defined analogue standard but a tightly controlled digital one upon which the clever hacks that eke full colour composite video from a single digital I/O pin will have little effect. Surely creating them from a simple microcontroller will be impossible! Not according to [techtoys], who has created an Arduino shield that creates an HDMI output from an SPI control input.

At its heart are two interesting integrated circuits that give us a little bit of insight into creating graphics at this level. First up is an RA8876 MIPI TFT controller which is a full graphics engine that produces a digital RGB output, followed by a CH7035B HDMI encoder that produces an HDMI output from the RGB. This combination of chips is particularly interesting one, because the RA8876 supports a variety of different interfaces that between them should be able to talk to most microcontrollers. In the Arduino world the only other HDMI options come via the use of an FPGA.

This is a project that seems to have been around for a couple of years, but which is still an active one. The classic Arduino shield form factor may now seem a little past its zenith, but as this board shows it’s still capable of being used for interesting new applications.

Thanks [th_in_gs] for the tip.

CampZone 2019 Badge Is Begging To Become A Huge Billboard

July 25, 2019 by 16 Comments

What has 256 full-colour LEDs, everyone’s favorite Lithium battery form factor, wireless connectivity, and hangs around your neck? It’s the CampZone 2019 badge that turns all attendees into a really fun billboard — but can the attendees hack themselves into one massive display?

One of Europe’s larger events for the gaming community,  CampZone is hosted in Netherlands and runs from July 26th to August 5th. It’s a typical large summer camp, and caters for those who intersect gaming and hacking with HackZone, a decent sized hacker camp within a camp. I’ve been fortunate enough to get my hands on a CampZone 2019 badge, dubbed the I-Pane, let’s take a look at what they managed to pack into this electronic conference badge.

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Forget The Walkman: It’s The Headphones

July 22, 2019 by 27 Comments

Forty years ago this month, a product was launched  in Japan that would have such a huge impact on the consumer electronics market that we are still using its descendants today. The story goes that one of the Sony founders would listen to music while traveling for the business, and found the company’s existing products cumbersome and awkward so asked his engineers to design something more convenient.

The resulting prototype became the Sony MDL-3L2, a set of miniaturised hi-fi headphones with distinctive foam earpads and a sliding metal headband that in total weighed an astoundingly svelte 45 g. It was paired with a cassette player called a “Walkman” derived from the company’s existing recorder that had been intended for journalists, and went on to sell in the millions. The market for headphones would never be the same again, and if you have a set of lightweight cans in your possession then this was their revolutionary progenitor.

But Hang On, What’s So Special About Headphones?

You probably won’t have heard the Walkman’s 40th anniversary described in those terms in the various reports covering the event, because of course the social impact of the portable music player rather than its headphones is what people remember. The joy of making a mix tape, of listening to The Human League on the bus, and of the adult disapproval of anything involving Kids Having Fun. Previously, music had been a static affair involving bulky record players, but now it could be taken anywhere. The other youth audio icon of that era, the boombox, simply couldn’t match the Walkman, and everybody wanted one.
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Making Instant Ramen A Bit More Instant

July 21, 2019 by 32 Comments

Instant ramen, the favoured repast of the impecunious would-be tech genius! It’s cheap, of dubious nutritional value, and it only takes a minute to cook. But what if you are in the creative Zone to the extent that five minutes to boil water is too much? For that you need an automatic ramen cooker, which is what [Mayermakes] has created from an upcycled electric filter coffee maker.

A filter coffee maker is a surprisingly effective instant ramen cooker without modification, in that it already contains a hotplate and water boiler to dribble hot water on some noodles. But it lacks any means of adding the seasoning or the essential hot sauce, so he created a 3D-printed rotating hopper driven by a stepper motor, and a servo driven syringe, while coffee maker itself is given a solid state relay to switch it on.

Controlling the show is an Arduino MKR board, which serves up a web interface with the option of ramen as it comes, or ramen with hot sauce. The result is an automated pot of $0.49 noodles that will set no gourmet’s heart a-flutter. Then again, fine dining is not why instant ramen exists.

This appears to be our first ramen-cooking coffee pot, but we have seen a guitar made from noodles!

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A New Motherboard For Amiga, The Platform That Refuses To Die

July 21, 2019 by 34 Comments

If you go out and buy a computer right now, how many choices do you really have? Generally speaking, there’s PC or Mac. If we were being generous you could consider Chromebook and perhaps even mobile, but let’s be honest, computing is a two-party system with the ability to dump the OS and run Linux as the obvious third-party disruptor. It wasn’t always like this.

In the early years of personal computing there were a slew of serious contenders. A PC, a Mac, an Atari ST, an Amiga, and several more that all demanded serious consideration on the general purpose desktop computer market. Of all these platforms, the Amiga somehow stubbornly refuses to die. The Amiga 1200+ from [Jeroen Vandezande] is the latest in a long procession of post-Commodore Amigas, and as its name suggests it provides an upgrade for the popular early-1990s all-in-one Amiga model.

It takes the form of a well-executed open-source PCB that’s a drop-in replacement for the original A1200 motherboard. CPU, RAM, and video are broken out onto daughterboards, with PCMCIA replaced by an SD card slot. The catch: it does require all the custom Amiga chips from a donor board.

The original Amiga 1200 was a significant upgrade to the architecture of the 1980s originals, and this certainly provides a much-needed enhancement to its underwhelming 68EC020 processor. It’s fair to say that this is the Amiga upgrade we’d all have loved to see in about 1996 rather than waiting until 2019. It’s still a delight for a retrogaming enthusiast; many of those who keep it alive remember the Amiga was the best multimedia platform that could be had for a few glorious years.

We’ve brought you a host of Amiga projects over the years, including the resurrection of an A500 and of course another A1200 PCB.

Thanks to [Eric Hill] for the tip.