The Hot Chocolate Effect Explained

December 17, 2023 by 19 Comments

This is the time of year when people in the Northern Hemisphere like to enjoy hot beverages like hot chocolate. [The Action Lab] uses hot chocolate to demonstrate an odd acoustic effect. Tapping a container of hot chocolate — or even just hot water — will make a sound at a certain frequency. But if you keep tapping, the frequency of the sound will gradually increase. Don’t know why? Don’t worry, neither did scientists until around 1980.

The secret is bubbles and the speed of sound through air vs a liquid. The speed of sound in the liquid and the height of the liquid in the cup set the frequency. However, the speed of sound changes based on the bubbles, which alters the frequency.

Continue reading “The Hot Chocolate Effect Explained” →

Hackaday Links Column Banner

Hackaday Links: December 17, 2023

December 17, 2023 by 16 Comments

Disappointing news from the US Senate this week as the “AM Radio for Every Vehicle Act” failed to advance in the sausage-making legislative process. We’ve previously covered this bill, which aims to force vehicle manufacturers to provide the means to receive terrestrial AM broadcasts in their cars and trucks without the need for extra subscriptions or charges. The bill’s sponsors tried to get it through on a “unanimous consent” maneuver, but Senator Rand Paul decided he didn’t like the idea of the government mandating what equipment cars should have. The coverage we’ve seen on this bill leads us to believe its sponsors are missing the point. Instead of pitching this as an issue of freedom of choice in entertainment, what they should be concentrating on is the safety aspect of AM radio. We’ve seen how much the government has invested in keeping AM stations on the air in just about any foreseeable emergency, so it’s only natural to look at a car’s AM radio as essential safety equipment like airbags, antilock brakes, and backup cameras. Seems like that’s something that everyone can agree on.  Continue reading “Hackaday Links: December 17, 2023” →

Second Life UPS Mark II: A UPS For Low-Voltage DC Applications

December 17, 2023 by 17 Comments

When you have a whole stack of devices and appliances that all have an AC to DC adapter and which you’d like to put on an uninterruptable power supply (UPS), you could do the obvious thing and get an off-the-shelf UPS with myriad AC outputs. In the case of a 19″ rack this means wrangling a power strip or two and any combination of differently sized AC/DC adapters into the rack, with questionable efficiency and waste heat dumped into the rack. This is where a DC-only UPS like [Maciej Grela]’s Second Life UPS Mark II provides an interesting alternative.

At its core it’s a pretty simple concept: A single 400Watt power supply handles the AC/DC conversion from mains to 24 VDC, which feeds the battery charger as well as the outputs. These outputs include 5 VDC, 12 VDC and Vrail, with the latter being either the output from the PSU, or the battery voltage. In case of AC power failure, an LT4416 dual power path controller handles the switch-over from the PSU output to the internal batteries. In the article, [Maciej] covers how the buck modules for the 12 & 5 VDC rails were sized, along with the conversion of an old rack-mounted network switch into a UPS. Continue reading “Second Life UPS Mark II: A UPS For Low-Voltage DC Applications” →

Mind Control… No, Not Like That

December 17, 2023 by 6 Comments

[Vintage Geek] found an interesting device from 1996 called “MindDrive” which claims you can control your computer with your brain. Oddly, though, it doesn’t connect to your head. Instead, it has a little finger sensor that looks like a pulse-ox sensor. Did it work? The video below will show you what it can and can’t do.

The company claims the device is the result of seven years of research. We suspect it is little more than a galvanometer, like a kid’s toy lie detector. There is a gold sensor and a Velcro strap. It is hard to imagine that it was feasible that “thinking left” would cause a change in your finger that the device can interpret.

Continue reading “Mind Control… No, Not Like That” →

The Dark Side Of Hacking XMas Lights, Literally

December 17, 2023 by 18 Comments

When looking at the piles of cheap RGB, Bluetooth-controlled LED strips you can find for sale just about anywhere these days, integrating them into a home-automation setup is very tempting. Normally these strips are controlled via a special smartphone app, that speaks whatever dodgy protocol was thrown together for the LED strip controller in question. Reverse-engineering this Bluetooth protocol is fairly easy these days, as [Will Cooke] describes in a recent tutorial, although for him there was a bit of a tragic ending with one particular RGB set.

With previous experiences reverse-engineering the Bluetooth protocol with Wireshark under his belt and having published the BJ_LED repository for LED strips that use the MohuanLED app, reverse-engineering this new LED strip with the associated “iDeal LED” app seemed fairly routine. Initially it was indeed routine, with just a curveball in the form of some encryption that the Jadx decompiler used on the app couldn’t help with. Fortunately the key ended up floating around on the internet, and the protocol was wide open. That’s when disaster struck.

While trying to throw payloads at the LED controller to find hidden modes and settings, [Will] found that he could indeed increase the brightness beyond what the app supported, but poking at lighting modes beyond the 10 presets gave a nasty shock. Modes 1 through 10 worked fine, 11 also did something new, but when the controller was asked to switch to mode 12, it shut off. Permanently. Whether this corrupted the firmware or caused some other issue is unknown, but it’s a clear warning that reverse-engineering comes with potentially fried hardware.

We hope that [Will] can get an autopsy performed on this controller to see the cause of this seemingly permanent failure that persisted across hard resets and disconnecting from power overnight. The protocol for this controller has been published on GitHub for those who’d like to take their chances.

LED lights: LadyAda, CC BY-SA 4.0.

Calculation Before We Went Digital

December 17, 2023 by 18 Comments

We have to like [Nicola Marras]. First, he wrote a great mini-book about analog computers. Then he translated it into English. Finally, he opened with a picture of Mr. Spock using an E6-B flight slide rule. What’s not to like? We suggest you settle in when you want to read it — there are almost 60 pages of text, photos, and old ads for things like slide rules and adding machines.

There is a lot of research here. We couldn’t think of anything missed. There’s a Pascalina, Ishango’s bone, a Babylonian spreadsheet, an abacus, and even Quipu. Toward the end, he gets to nomographs, adding machines, and the early calculators.

Continue reading “Calculation Before We Went Digital” →

The Laptop Every British Kid Would Have Wanted For Christmas 1983

December 17, 2023 by 12 Comments

How can we convey to a world in which a 64-bit laptop can be a near-throwaway item, just how amazing a miniature laptop version of the 1980s Sinclair ZX Spectrum could have been? perhaps we don’t need to, because here in 2023 there’s a real one for all middle-aged geeks who had the original to drool over.

8-bit home computers were super-exciting for the kids of the day, but they were in no way portable and relied on a TV, frequently the family model in the living room. It’s safe to say that a portable version of one of those home computers, not in an Osborne-style luggable case but in a clamshell palmtop, would have been mind-blowing, so four decades later we’re fascinated by [Airrr17]’s portable Sinclair ZX Spectrum.

At its heart is a dev board using one of the STM32F4 series microcontrollers, and running the Spectrum as an emulator. Alongside that is an LCD, and perhaps what is physically the best part of this, a Spectrum keyboard complete with BASIC keyword decals, made with large-button tactile switches that have we think, printed paper on top. Add in a small lithium-polymer cell and associated electronics in a cute little palmtop case, and it’s about as good a portable Sinclair as we could have imagined. All the details can be found in a GitHub repository, and as if that weren’t enough there’s an assembly video we’ve placed below the break.

Continue reading “The Laptop Every British Kid Would Have Wanted For Christmas 1983” →