Over on his YouTube channel [Aaron Danner] explains biasing transistors with current sources in the 29th video of his Transistors Series. In this video, he shows how to replace a bias resistor (and consequently an additional capacitor) with a current source for both common-emitter and common-collector amplifiers.
A current source provides electrical energy with a constant current. The implication is that if the resistance of the load changes the current source will vary the voltage to compensate. In reality, this is exactly what you want. The usual resistor biasing arrangement just simulates this over a narrow voltage range, which is generally good enough, but not as good as a true current source.
At Hackaday, it is always clock time, and clock time is a great time to check in with [shiura], whose 3D Printed Perpetual Calendar Clock is now at Version 2. A 3D printed calendar clock, well, no big deal, right? Grab a few steppers, slap in an ESP32 to connect to a time server, and you’re good. That’s where most of us would probably go, but most of us aren’t [shiura], who has some real mechanical chops.
There’s also a 24-hour dial, because why not?
This clock isn’t all mechanical. It probably could be, but at its core it uses a commercial quartz movement — you know, the cheap ones that take a single double-A battery. The only restriction is that the length of the hour axis must be twelve millimeters or more. Aside from that, a few self-tapping screws and an M8 nut, everything else is fully 3D printed.
From that simple quartz movement, [shiura]’s clock tracks not only the day of the week, the month and date — even in Febuary, and even compensating for leap years. Except for the inevitable drift (and battery changes) you should not have to adjust this clock until March 2100, assuming both you and the 3D printed mechanism live that long. Version one actually did all this, too, but somehow we missed it; version two has some improvements to aesthetics and usability. Take a tour of the mechanism in the video after the break.
Water is an excellent coolant, but the flip side is that it is also an excellent solvent. This, in short, is why any water cooling loop is also a prime candidate for an interesting introduction to the galvanic metal series, resulting in severe corrosion that commences immediately. In a recent video by [der8aer], this issue is demonstrated using a GPU cold plate. The part is made out of nickel-plated copper and features many small channels to increase surface area with the coolant.
The surface analysis of the sample cold plate after a brief exposure to distilled water shows the deposited copper atoms. (Credit: der8auer, YouTube)
Theoretically, if one were to use distilled water in a coolant loop that contains a single type of metal (like copper), there would be no issue. As [der8auer] points out, fittings, radiators, and the cooling block are nearly always made of various metals and alloys like brass, for example. This thus creates the setup for galvanic corrosion, whereby one metal acts as the anode and the other as a cathode. While this is desirable in batteries, for a cooling loop, this means that the water strips metal ions off the anode and deposits them on the cathode metal.
The nickel-plated cold plate should be immune to this if the plating were perfect. However, as demonstrated in the video, even a brief exposure to distilled water at 60°C induced strong galvanic corrosion. Analysis in an SEM showed that the imperfect nickel plating allowed copper ions to be dissolved into the water before being deposited on top of the nickel (cathode). In a comparison with another sample that had a coolant with corrosion inhibitor (DP Ultra) used, no such corrosion was observed, even after much longer exposure.
This DP Ultra coolant is mostly distilled water but has glycol added. The glycol improves the pH and coats surfaces to prevent galvanic corrosion. The other element is benzotriazole, which provides similar benefits. Of course, each corrosion inhibitor targets a specific environment, and there is also the issue with organic films forming, which may require biocides to be added. As usual, water cooling has more subtlety than you’d expect.
China played host to what, presumably, was the world’s first robot and human half-marathon. You can check out the action and the Tiangong Ultra robot that won in the video below. The event took place in Beijing and spanned 21.1 km. There was, however, a barrier between lanes for humans and machines.
The human rules were the same as you’d expect, but the robots did need a few concessions, such as battery swap stops. The winning ‘bot crossed the finish line in just over 160 minutes. However, there were awards for endurance, gait design, and design innovation.
We appear to be edging ever closer to a solid statement of “We are not alone” in the universe with this week’s announcement of the detection of biosignatures in the atmosphere of exoplanet K2-18b. The planet, which is 124 light-years away, has been the focus of much attention since it was discovered in 2015 using the Kepler space telescope because it lies in the habitable zone around its red-dwarf star. Initial observations with Hubble indicated the presence of water vapor, and follow-up investigations using the James Webb Space Telescope detected all sorts of goodies in the atmosphere, including carbon dioxide and methane. But more recently, JWST saw signs of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), organic molecules which, on Earth, are strongly associated with biological processes in marine bacteria and phytoplankton.
Forth is popular on small computers because it is simple to implement, yet quite powerful. But what happens when you really need to shrink it? Well, if your target is the 6502, there’s milliForth-6502.
This is a port of milliForth, which is a fork of sectorforth. The sectorforth project set the standard, implementing a Forth so small it could fit in a 512-byte boot sector. The milliForth project took sectorforth and made it even smaller, weighing in at only 336 bytes. However, both milliForth and sectorforth are for the x86 architecture. With milliForth-6502, [Alvaro G. S. Barcellos] wanted to see how small he could make a 6502 implementation.
Despite the best efforts of the RepRap community over the last twenty years, self-replicating 3D printers have remained a stubbornly elusive goal, largely due to the difficulty of printing electronics. [Brian Minnick]’s fully-printed 3D printer could eventually change that, and he’s already solved an impressive number of technical challenges in the process.
[Brian]’s first step was to make a 3D-printable motor. Instead of the more conventional stepper motors, he designed a fully 3D-printed 3-pole brushed motor. The motor coils are made from solder paste, which the printer applies using a custom syringe-based extruder. The paste is then sintered at a moderate temperature, resulting in traces with a resistivity as low as 0.001 Ω mm, low enough to make effective magnetic coils.
