If your interest lies with robotics there are a multitude of different platforms for you to build. [Teemu Laurila] was frustrated with what was on offer, so designed his own with four-wheel double wishbone suspension and mecanum wheels for maximum flexibility.
It’s a design that has been through multiple revisions since its first iteration in 2015, and along the way it’s clear some thought has gone into it. That double wishbone suspension features an angle for a high ground clearance, and is fully sprung. Drive comes from small motor/gearboxes at each axle. The chassis meanwhile has plenty of space for a single-board computer, and has been specifically designed with the BeagleBone Black in mind.
This build isn’t fully DIY, as the mecanum wheels appear to be off-the-shelf items, but the rest of the project makes up for this. If you need to make your own, it’s hardly as though there aren’t any projects from which you can borrow components.
Pen plotters, those mechanical X-Y drawing machines that have in many cases been superseded by inkjet and other printer technologies, exert a fascination from a section of our community. Both analogue and digital machines are brought out of retirement for some impressive graphical effects, and we suspect that more than one of you wishes you had the space for one in your lives.
The good news is that you now no longer need room for a hefty piece of 1970s instrumentation, because the ever-inventive [Bart Dring] has produced a tiny 3D-printed plotter with an ESP32 at its heart. The ESP runs his ESP32 port of the Grbl firmware, and can handle a G-code file placed wirelessly upon the controller’s SD card.
The mechanism is particularly clever, using a single belt for both X and Y axes. The pen lift Z axis is a hinged design rather than a linear one, with a hobby servo doing the lifting. The hinge bearings are placed as close as possible to the paper surface to achieve an approximation to a vertical lift. You can see the machine in action in the video below the break, drawing its own self-portrait.
If you are a long-time reader you will recognise [Bart]’s work, he has appeared here quite a few times. His coaster-cutting machine and his CNC plotter badge are particularly memorable.
Free-form circuitry built as open wire sculpture can produce beautiful pieces of electronics, but it does not always lend itself to situations in which it might be placed under physical stress. Thus the sight of [Mile]’s free-form wristwatch is something of a surprise, as a wristwatch cam be exposed to significant mechanical stress in its everyday use.
A wire Wrencher graces the underside.
The electronic side of this watch is hardly unusual, the familiar ATmega328-AU low-power microcontroller drives a tiny OLED display. Mechanically though it is a different story, as the outline of a wristwatch shell is traced in copper wire with a very neat rendition of a Wrencher in its base, and a glass lens is installed over the screen to take the place of a watch glass. A strap completes the wristwatch, which can then be worn like any other. Power comes from a small 110 mAh lithium-polymer cell, which it is claimed gives between 6 and 7 hours of on time and over a month of standby with moderate use.
Unfortunately there does not seem to be much detail about the software in this project, but since ATmega328 clocks and watches are ten a penny we don’t think that’s a problem. The key feature is that free-form construction, and for that we like it a lot.
A hi-fi amplifier used to be a rite of passage for the home electronic constructor, back in the days when consumer electronics was still dominated by analogue entertainment. It’s unusual then to see [carbono.silício]’s stereo amplifier project, constructed in an open-wire circuit sculpture form on a log. You didn’t read that incorrectly, it’s built not on a breadboard but on a piece of Olea Maderensis, or Madiera Olive wood, complete with bark. This endangered tree was not felled, instead it was a piece blown down after a storm.
The circuit is slightly unusual for a project such as this, in that it uses a pair of LM386 audio amplifier chips. This isn’t an unusual component, but it’s one more commonly seen providing the amplification for a small speaker project than in a stereo hi-fi amplifier. But the construction is beautifully done, with very neatly routed wires, a single central volume knob, and a blue LED power light. A particularly nice touch are the aluminium electrolytic capacitors, we suspect having had their plastic sleeving removed.
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.
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.
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?
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.
