Mysterious Files PH

Solar power has gotten cheap enough that putting up panels is among the cheapest ways of providing energy. This isn’t just the case for bulk electricity on a power grid, either; even small devices are easier and cheaper to power with solar than ever before. For example, landscape lighting which once relied on 12V or 24V DC wires all over one’s yard with a transformer and power supply hidden somewhere have partially been converted to simpler individual solar-powered lights now. These small devices can also be given additional capabilities as [Mauro] demonstrates.

In this case, [Mauro]’s goal was to add on-demand lighting to a solar-powered light which was otherwise motion-activated only. To do this, they added a NRF24L01+ radio inside the light’s housing paired with an STM32 microcontroller. This secondary system is largely separated from the existing control circuitry with the exception of being able to switch the lights and receiving its power from the same solar panel. [Mauro] also created a small library to help with communicating with these new modules, whether that’s using a home automation system like Home Assistant or some other method.

Although adding in a few capabilities to inexpensive solar lighting might seem simple on the surface, a project like this is a gateway to adding in all kinds of interesting features to things with built-in solar panels and lots of free space in their cases. The best example here is the addition of a Meshtastic node to one of these lights, making it convenient and stealthy, but we could also see adding in other remote hardware to a landscape lighting module like a gate sensor or a plant health monitoring system.

A die filer is a useful tool to have if you find yourself filing parts on the regular. It’s basically a machine that reciprocates a file up and down for you so you can focus on filing the part to your desired dimensions. They’re not commonly manufactured these days, so [Richard Huberjohn] set about building his own. 

This die filer relies on a simple mechanism to turn rotational motion from a motor into reciprocating linear motion in the vertical plane. A rotating shaft is connected to a crank, which turns a pin in a slotted carrier attached to a linear bearing. As the wheel turns, the pin slides in the carrier, driving it and the linear rod up and down in turn. Attach a file to this, and you have a working die filer. In this case, the rotating shaft is driven by a pair of DC brushed motors, with output stepped down via a gearbox and then a short belt drive. Speed is varied with the aid of an off-the-shelf controller.

If you’re regularly filing small parts, a build like this could speed your work to a great degree. We’ve featured other DIY machine tool builds before, too. If you’re cooking up your own gear for the home workshop, don’t hesitate to let us know on the tipsline!

The IKEA SKAFTSÄRV is an economical LED accent lamp, but while highly affordable it has only fixed lighting options. [simoneluconi] shows how it can easily be turned into a fully-configurable, WLED-connected, WiFi-enabled RGB lamp with little more than an ESP32-based board.

To do this, the control board of the lamp gets replaced with an ESP32-C3 Super Mini board. Control and automation comes from WLED, open-source software that offers flexible automation and control for LED lights with a wide range of features, including native Android and iOS apps.

Modifying the SKAFTSÄRV lamp is fairly straightforward, but opening the unit does require breaking some glued seams to get inside. Once that’s done, the replacement board fits nicely into the housing and the unit can be closed back up. As far as WLED is concerned, the new lamp has 30 LEDs, WS281x type, GRB color order.

The end result is a stylish accent lamp with built-in diffusor and mount that can be controlled over WiFi with all the features WLED brings, such as easy integration with Home Assistant.

This isn’t the first time IKEA’s LED lighting has been given a powerup. Their pixel-style LED wall-mounted OBEGRÄNSAD, which displays a few canned animations out of the box, got considerably enhanced with a new controller.

Thanks [Crash] for the tip!

You probably flash new firmware on a variety of devices regularly, even though that’s rare for non-technical types. But what about your hard drive firmware? Most of us don’t want to touch our operating drives, so unless you are dealing with surplus drives or have a special project in mind, you may not think much about the firmware running your spinning rust storage. [I Code 4 Coffee] uses hard drives in an unusual way to exploit Xbox 360s, and wound up reverse engineering some drive firmware with an eye to making changes.

The analysis started with three hard drives and an SSD. Looking for people who’ve done similar work wasn’t as productive as you might think. There isn’t much call for modifying hard drive firmware, and what data there is can be outdated.

One thing that was available was firmware dumps taken with a PC-3000 data recovery tool. What follows is a deep dive down the hard drive rabbit hole. There are backdoor vendor commands and connections to the diagnostic RS-232 port on some drives. You can find the technical artifacts on GitHub.

We learned a few things, and we bet you will too. Another way to get into the hard drive’s firmware is via JTAG.

If you want to maximize the life of your lithium-ion batteries, proper storage voltage is critical. That is, don’t store them empty, and don’t store them completely full either. “Almost fully charged” is a sweet spot for occasional-use devices. Sadly, this is easier said than done. While many devices use integrated rechargeable batteries these days, most provide no method of limiting charge level. That’s where [DaverDavid]’s ChargeCap comes in.

ChargeCap sits between a USB charger and target device, disconnecting when it detects that recharging is 80 to 90 percent complete. This is particularly useful for maximizing the cell life of devices that see only intermittent use.

The way ChargeCap does this is clever, and relies on the fact that all lithium-ion charging curves look the same regardless of cell capacity or cell count. Charge current remains at pretty much the same level for most of the charging process, but tapers off quickly (and in a linear fashion) as cells approach their maximum capacity. That’s because charging a battery is a lot like blowing up a balloon: the first breaths are easy, but once the balloon fills out, every breath needs to push harder than the last.

ChargeCap works by sampling the peak charge current at the beginning of the charge cycle, then detecting when it drops below 50 percent of peak, at which point charging is stopped. The result is a device that reliably charges to 80 to 90 percent of capacity, and no more. ChargeCap uses an ESP32-C3 and a small OLED display that, as a nice touch, inverts colors to signal charge completion. Design files and code are at the GitHub repository.

Lithium-ion cells are fantastic devices, so flesh out your knowledge by reading [Arya Voronova]’s primer on designing them into your own projects, or a more in-depth explanation of how they work.

Three resistors in parallel: 4.7 k,Ω 22 kΩ, and 3.3 kΩ. Quick! What’s the equivalent value? You can estimate it, of course, but if you want the actual 1.8 kΩ (approximately) answer, you probably reached for some kind of calculating aid. I have two slide rules on my desk, and plenty more a few steps away, but I don’t use them much, honestly. I have a very old HP-41C — arguably the best calculator ever made — but I am usually afraid to use it as it is almost 50 years old and difficult to repair. I also have an HP-28S on my desk, a replica HP-41C, and a few others in desk drawers. There are also dozens of calculators on my desktop computer, my phone –including the official HP Prime app — and the web browser.

I often see newer calculators from HP, like the Prime G2, or “new” HP-like calculators like the ones from SwissMicros, and think I should pick one up. Well, technically, HP licensed their calculators to Moravia, so even a “real” HP calculator isn’t from HP anymore. But, in the end, I always realize that my need for a physical calculator is so diminished that I can’t justify buying anything new, and I can barely even spring for a $10 one at the thrift store unless it is a real collectible.

Mind you, I’m not talking about RPN versus algebraic. I could say the same thing for TI, Casio, or Sharp calculators. I just don’t know why I need one anymore, even though I still, for some strange reason, want them.

For the record, I did use an HP-41C to check the resistor math, but it was in the form of an app on my phone, not a real calculator. On the same computer I’m writing this on, I have HP-41C emulators, the Prime emulator, and a bunch of other calculators. Yet I still pick up my phone and use the familiar key layout of the HP-41C. I don’t know why. The replica 41C, unfortunately, has a landscape-oriented keyboard, so while I like it, it doesn’t satisfy my finger’s muscle memory.

Which leads to this Ask Hackaday. Do you use a calculator? Why? If you don’t, do you use a fake calculator on your phone or computer? Or do you just send your math to Google or Wolfram? I suspect some of the answer will be generational. I was in high school before calculators started showing up in schools, but they took over quickly.

There is something satisfying about having a purpose-built device to do your math. No long boot sequence. No switching apps. No messages coming in while you are typing in numbers. For the ultimate convenience, you could wear it on your wrist. The Apollo mission that docked with a Russian spacecraft carried an HP-65, and nine early Space Shuttle missions used an HP-41C. But even astronauts now don’t have a standard-issue calculator. Pilots sometimes use electronic E6Bs, but many still use the mechanical version.

Of course, I do collect slide rules, so maybe I just need to accept that calculators are yet another tech relic to collect. But someone is still buying them. I’d like to be one of them.

With the current state of tech, you can easily build your own calculators. There are several options.