If you’ve heard the high-pitched whine or buzz from an electronic device when a current-carrying inductor is vibrating, you’ll know how unpleasant it can be. It’s common in all kinds of equipment, but it’s become a particular annoyance of late in hardware like PC power supplies, GPUs, and cooling pumps. There is plenty of hearsay on the web about which parts whine and which don’t, and [Lowell Wood] wants to get to the bottom of it. 

To track the issue, [Lowell] has put together the Coil Whine Database. It accepts user reports on hardware, regarding the level at which coil whine is present. A score of 0 is given to a part that is inaudible in a quiet room, with higher scores representing higher sound levels. A part scored at 2 is audible working at a desk with the computer under load; a part scored at 4 is audible even when the machine or device is at idle.

For now, the database is largely empty—[Lowell] has just opened submissions, adding a report on their own ROG Astral RTX 5080 card for good measure. If you want to submit a report on a unit, either silent or noisy, that’s simple enough—just fill in the coil whine report form. Over time, submissions will hopefully grow, and it will be easier to get a good idea of what equipment whines and what is likely to operate silently out of the box.

The database aims to present a guide to what parts whine, and how much, noting that any given population of devices tends to vary. To that end, any given device won’t be reported on publicly until it receives at least 5 reports. To counter bias, reports of silent parts will be weighted higher, since it’s unlikely that people happy with their quiet hardware will be rushing to research this issue or report it to a database. Relevant files to the project are available on GitHub for the curious.

This database could be a great boon to the brigade of PC builders out there who like their machines to be as silent as possible. If that sort of thing appeals to you, it’s probably time you started researching passive cooling as well…

Modern heat pumps, of which air conditioners are a subset, seem like simple machines in theory. They just move heat from one place to another. But in order to operate efficiently, they need specific temperatures and humidities on either side of the pump or they can behave in non-ideal ways. [GreatScott!] noticed this when his air conditioner worked well during a heatwave, but started acting anemic once the outside air temperature cooled down. At once point it was barely able to bring his indoor house temperature below the temperature outside, and he went on a deep dive to investigate why this would be and then found a way trick his air conditioner into working outside its designed temperature range.

Many things can cause this behavior, and some of them are indicative of malfunctions like low refrigerant levels or problems with the compressor or control circuitry. But [GreatScott!]’s unit is pretty new so it was unlikely to be something like that. To investigate, he built a circuit with a small heater which is paired to the outdoor heat exchanger’s temperature probe, tricking the control circuitry into working in a different mode. With a few temperature sensors inside and outside, this was enough to kick the air conditioner into high gear and start outputting cold air again.

While noting that we aren’t HVAC experts, there are a few things that could cause this. One of which is high indoor humidity which might be likely for Germany in the summer, or the outdoor condenser needing a certain temperature or pressure range to operate efficiently. Whatever the case, [GreatScott!] decided to remove his creation to keep from inadvertently damaging his air conditioner. It is possible, however, to use a bit of machine learning to find out more about why one’s HVAC system isn’t behaving as well as it should.

There’s plenty of substances that can theoretically be extruded from a nozzle, but only a regrettably small subset of them can actually be used for 3D printing. One limiting factor is the liquid range: too high a melting point and it’s hard to reliably extrude, too low and it tends to ooze and flow once extruded. Embedded 3D printing offers a way around this: it submerges the entire print in a shear-thinning support gel which keeps liquids in place until they solidify. [Riley] of Riley’s Lab recently built such a 3D printer and used it to print in silicone and epoxy.

In place of the extruder, [Riley] mounted a mostly 3D printed syringe pump, which allowed him to squirt out almost any liquid. For a test, he printed a tardigrade model out of cream cheese. This was a good test material for several reasons: it’s cheap, easy to extrude, and holds it shape well after extrusion. Silicone and epoxy, however, won’t hold their shape, which is where the support bath comes it. This was a mixture of mineral and vegetable oil, with some fumed silica added to make it thick yet shear-thinning. This lets it contain the extruded liquid, yet flow as the extrusion needle slices through it.

For the first test, [Riley] printed a Benchy out of Sylgard 184. The outcome looked good in the bath, bar some stringing, but it seemed to have limited adhesion between layers, and disintegrated upon removal from the bath. A second test with a two-part epoxy worked much better; it also had some stringing, but it held together while the bath was washed away in isopropyl alcohol, and even seemed decently shock-resistant afterwards.

It’s great to see a hacker working on this technology; we’ve previously covered a commercial take on it, as well as some of the research that led to it.