In [Big Clive]’s recent grab bag of tat ordered from Chinese commerce platforms, there were two touch light control boxes that can turn any ungrounded conductive surface into a mains load dimmer control. Of course, the primary reason for the purchase was a teardown, and a teardown we got.

These unassuming little boxes are built around the Tontek TT6061A, listed as a ‘touch dimmer’, which uses a triac to control the output current. There are four levels, ranging from off to full brightness, before the next touch event turns the output off again.

With the output off, [Clive] measured 0.7 W power usage. After popping open the plastic enclosure, the circuitry turned out to largely follow the recommended application circuit from the datasheet — as can be seen in the above screenshot — with apparently a few cost optimizations, in the form of omitted diodes and a capacitor.

The problem with these devices is that they are only really suitable for dimming low-power resistive loads like incandescent lights, with LED lights likely requiring the unpopulated capacitor spot on the PCB to be populated to tweak the chip’s triac timing, among other changes. There are also the slight issues with no real concern with them radiating EMI, and the exciting possibility of getting shocked at mains voltage without at least a class-Y capacitor installed.

Perhaps using a capacitive touch controller instead that works through plastic, for example, isn’t such a crazy alternative here, especially since they’re not really much more expensive and less likely to shock you. Want to create your own triac designs? We have just the post to get you started.

After having been sent a vacuum fluorescent display (VFD) based clock for a review, [Anthony Francis-Jones] took the opportunity to explain how these types of displays work.

Although VFDs are generally praised for their very pleasant appearance, they’re also relatively low-power compared to the similar cathode ray tubes. The tungsten wire cathode with its oxide coating produces the electrons whenever the relatively low supply voltage is applied, with a positively charged grid between it and the phosphors on the anode side inducing the accelerating force.

Although a few different digit control configurations exist, all VFDs follow this basic layout. The reason why they’re also called ‘cold cathode’ displays is because the cathode doesn’t heat up nearly as hot as those of a typical vacuum tube, at a mere 650 °C. Since this temperature is confined to the very fine cathode mesh, this is not noticeable outside of the glass envelope.

While LCDs and OLED displays have basically eradicated the VFD market, these phosphor-based displays still readily beat out LCDs when it comes to viewing angles, lack of polarization filter, brightness and low temperature performance, as LC displays become extremely sluggish in cold weather. Perhaps their biggest flaw is the need for a vacuum to work, inside very much breakable glass, as this is usually how VFDs die.

Akin to the razor-and-blades model, capsule-based coffee machines are an endless grind of overpriced pods and cheaply made machines that you’re supposed to throw out and buy a new one of, just so that you don’t waste all the proprietary pods you still have at home. What this also means is a seemingly endless supply of free broken capsule coffee makers that might be repairable. This is roughly how [Mark Furneaux] got into the habit of obtaining various Nespresso VertuoLine machines for attempted repairs.

The VirtuoLine machines feature the capsule with a bar code printed on the bottom of the lip, requiring the capsule to be spun around so that it can be read by the optical reader. Upon successful reading, the code is passed to the MCU after which the brewing process is either commenced or cruelly halted if the code fails. Two of the Vertuo Next machines that [Mark] got had such capsule reading errors, leading to a full teardown of the first after the scanner board turned out to work fine.

Long story short and many hours of scrubbed footage later, one machine was apparently missing the lens assembly on top of the photo diode and IR LED, while the other simply had these lenses gunked up with spilled coffee. Of course, getting to this lens assembly still required a full machine teardown, making cleaning it an arduous task.

Unfortunately the machine that had the missing lens assembly turned out to have another fault which even after hours of debugging remained elusive, but at least there was one working coffee machine afterwards to make a cup of joe to make [Mark] feel slightly better about his life choices. As for why the lens assembly was missing, it’s quite possible that someone else tried to repair the original fault, didn’t find it, and reassembled the machine without the lens before passing the problem on to the next victim.

Following up on user-reported cases of Battle Born LiFePO4 batteries displaying very hot positive terminals, [Will Prowse] decided to buy a brand new one of these LFP batteries for some controlled cycle testing.

Starting with 30 cycles with a charging current of 49 A and a discharge current of 99 A, this put it well within the 100 A continuous rating for the battery. There is also a surge current rating of 200 A for thirty seconds, but that was not tested here.

What’s interesting about the results here is that instead of the positive terminal getting visibly discolored as with the previous cases that we reported on, [Will] saw severe thermal effects on the side of the negative terminal to the point where the plastic enclosure was deforming due to severe internal heating.

During testing, the first two charge-discharge cycles showed full capacity, but after that the measured capacity became extremely erratic until the battery kept disconnecting randomly. After letting the battery cool down and trying again with 80 A discharge current the negative terminal side of the enclosure began to melt, which was a good hint to stop testing. After this the battery also couldn’t be charged any more by [Will]’s equipment, probably due to the sketchy contact inside the battery.

It’s clear that the plastic spacer inside the terminal bus bar was once again the primary cause, starting a cascade which resulted in not only the enclosure beginning to char and melt, but with heat damage visible throughout the battery. Considering that the battery was used as specified, without pushing its limits, it seems clear that nobody should be using these batteries for anything until Battle Born fixes what appears to be the sketchiest terminal and bus bar design ever seen in a high-current battery.

Since the RP2040 microcontroller is available as a stand-alone component, it’s easy enough for third parties to churn out their own variations — or outright clones of — the Raspberry Pi Pico. Thus we end up with for example AliExpress sellers offering their own versions that can be significantly cheaper than the genuine article. The ones that [electronupdate] obtained for a test and decapping session cost just $2.25 a pop.

As can be seen in the top image, the board from AliExpress misses the Raspberry Pi logo on the silkscreen for obvious reasons, but otherwise appears to feature an identical component layout. The QSPI Flash IC is marked on the die as BY250156FS, identifying it as a Boya part.

Niggles about flash ROM quality aside, what’s perhaps most interesting about this teardown is what eagle-eyed commentators spotted on the die shot of the RP2040. Although on the MCU the laser markings identify the RP2040 as a B2 stepping, the die clearly identifies it as an ‘RP2 B0’ part, meaning B0 stepping. This can be problematic when you try to use the USB functionality due to hardware USB bugs in the B0 and B1 steppings.

As they say, caveat emptor.

You don’t see them much anymore, but there was a time when any hobbyist who dealt with RF probably had a grid dip meter. The idea was to have an oscillator and measure the grid current as it coupled to external circuits. At resonance, the grid current would go down or dip, hence the name. In the hands of someone who knew how to use it, the meter could measure inductance, capacitance, tuned circuits, antennas, and more. [Thomas] takes a peek inside a homebrew unit from the 1950s in a recent video you can see below.

These meters often have a few things in common. They usually have a plug-in coil near the top and a big tuning capacitor. Of course, there’s also a meter. You have to pick the right coil for the frequency of interest, which both sets the oscillator frequency range and couples to the circuit under test.

The device has an odd case for a homebrew instrument. Whoever made it was an excellent metalworker. Inside was a neatly built circuit with an EC-81 triode and a unique selenium rectifier.

It would be nice to know who the unknown builder was, but with a bit of coaxing, the device still worked just fine. Of course, these days, you have many better options, but it is amazing what all this relatively simple device could do.

We’ve covered how these meters work before, including some pictures from our own benches.

Modern passenger airliners are essentially tubes-with-wings, they just happen to be tubes that are stuffed full with fancy electronics. Some of the most important of these are related to keeping the bits of the tube with humans inside it at temperatures and pressures that keeps them alive and happy. Case in point the Boeing 777, of which [Michel] of Le Labo de Michel on YouTube recently obtained the Cabin Pressure Control System (CPCS) for a teardown.

The crucial parts on the system are the two Nord-Micro C0002 piezo resistive pressure transducers, which measure the pressure inside the aircraft. These sensors, one of which is marked as ‘backup’, are read out by multiple ADCs connected to a couple of FPGAs. The system further has an ARINC 429 transceiver, for communicating with the other avionics components. Naturally the multiple PCBs are conformally coated and with vibration-proof interconnects.

Although it may seem like a lot of hardware just to measure air pressure with, this kind of hardware is meant to work without errors over the span of years, meaning significant amounts of redundancy and error checking has to be built-in. Tragic accidents such as Helios Airways Flight 522 involving a 737-300 highlight the importance of these systems. Although in that case human error had disabled the cabin pressurization, it shows just how hard it can be to detect hypoxia before it is too late.