LED Driver Circuit For Safety Hat Sucks Single AAA Cell Dry

[Petteri Aimonen] created an omnidirectional LED safety light to cling to his child’s winter hat in an effort to increase visibility during the dark winter months, but the design is also great example of how to use the Microchip MCP1640 — a regulated DC-DC step-up power supply that can run the LEDs off a single AAA cell. The chip also provides a few neat tricks, like single-button on/off functionality that fully disconnects the load, consuming only 1 µA in standby.

[Petteri]’s design delivers 3 mA to each of eight surface-mount LEDs (which he says is actually a bit too bright) for a total of about 20 hours from one alkaline AAA cell. The single-layer PCB is encased in a clear acrylic and polycarbonate enclosure to resist moisture. A transistor and a few passives allow a SPST switch to act as an on/off switch: a short press turns the unit on, and a long press of about a second turns it back off.

One side effect is that the “off” functionality will no longer work once the AAA cell drained too badly, but [Petteri] optimistically points out that this could be considered a feature: when the unit can no longer be turned off, it’s time to replace the battery!

The usual way to suck a battery dry is to use a Joule Thief, and while this design also lights LEDs, it offers more features and could be adapted for other uses easily. Interested? [Petteri] offers the schematic, KiCAD file for the PCB, and SVG drawing of the enclosure for download near the bottom of the project page.

A Very Tidy ATX Bench PSU

If there’s one thing that for decades of desktop PCs have given us, it’s a seemingly endless supply of relatively capable power supplies. If you need 5 volts or 12 volts at a respectable current they’re extremely useful, so quite a few people have used them as bench power supplies. Some of these builds box up the mess of wires into a set of more useful connectors, but [Joao Pinheiro] has taken his to the next level with a very neat 3D printed case and a set of variable switching regulators to make a variable bench supply with a top voltage of 60 volts.

In many ways it’s a straightforward wiring job to build, but there’s an unexpected power resistor involved. It’s sinking the 5 volt line, and we’re guessing that some current is required here for the PC power supply to run reliably. The thought of a high power resistor dumping heat into a 3D printed case leads us to expect that things might become a little melty though.

ATX power supplies are so numerous as to be expendable, so it’s always worth regarding them as a source of parts as well as a power supply.

Simple ATX Bench Power Supply Adds Variable Output

A benchtop power supply is a key thing to have for any aspiring electronics hacker. While you can always buy one, plenty of us have old computer PSUs lying around that could do a fine job themselves. [Frugha] decided to whip up a neat 3D-printed design for converting any ATX PSU into a usable bench unit.

The design features banana plugs outputting +12V, -12V, +5V, and +3.3V, with all outputs appropriately fused for safety. There’s also a fused stepdown converter used to supply variable voltages as needed. Its original trimpot was replaced with a multi-turn pot for ease of control. To make everything work, a load resistor on the 5V circuit makes the power supply think it’s hooked up to a motherboard. It’s all wrapped up in a neat slant-sided 3D-printed case that fits onto the ATX power supply itself.

The result is a neat and tidy power supply built out of readily-available components. We particularly like the addition of the stepdown converter – most ATX-based projects don’t offer variable output, which can nonetheless come in handy.

We’ve seen some other great builds along these lines before, too. If you’ve been cooking up your own homebrew power supply, don’t hesitate to share it on the tipsline! 

Rescue That Dead Xbox With An External PSU

There is nothing worse than that sinking feeling as a computer or other device fails just after its warranty has expired. [Robotanv] had it with his Xbox Series S whose power supply failed, and was faced with either an online sourced PSU of uncertain provenance, or a hefty bill from Microsoft for a repair. He chose to do neither, opening up his console and replacing the broken PSU with a generic external model. See the video below the break.

The Xbox appears surprisingly well designed as a modular unit, so accessing and unplugging its PSU was quite easy. To his surprise he found that the connections were simply two wires, positive and negative lines for 12 V. The solution was to find a suitably beefy 12 V supply and wire it up, before continuing gaming.

Beyond that simple description lies a bit more. The original was a 160 W unit so he’s taken a gamble with a 120 W external brick. He’s monitoring its temperature carefully to make sure, but with his gaming it has not been a problem. Then there’s the board wiring, which he appears to have soldered to pads on the PCB. We might have tried to find something that fit the original spade connectors instead, but yet again it hasn’t caused him any problems. We’d be curious to see what has failed in the original PSU. Meanwhile we’re glad to see this Xbox ride again, it’s more than can be said for one belonging to a Hackaday colleague.

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USB Power Isolator Keeps Smoke In

Anyone who’s done an electronics project knows the most important part of any good design is making sure to keep the magic smoke inside of all of the components. There are a lot of ways to make sure the smoke stays in there, but one of the most important is making sure that the power supply is isolated. If you’re using a USB port on a computer as your power source, though, it can be a little more complicated to isolate it from the computer.

The power supply is based around a small transformer with a set of diodes to act as a rectifier. Of course, while a transformer is great at isolating power supplies, it isn’t much good at DC. That’s what the ATtiny microcontroller is for. It handles the high-speed switching of the MOSFETs, which drive the transformer and handle some power regulation. There are two different power supplies created as part of this project as well — the first generates +5V much like a normal USB plug would have, and the other creates both +5V and -5V. It will be important not to mix these two up, or that tricky blue smoke may escape.

The project page goes into extensive details on the operation of the device, so if electrical theory is of interest, this will definitely be worth a read. Isolating a valuable computer from a prototype circuit is certainly important, but if you’re looking for a way to isolate a complete USB connection, look at this build which includes isolation for a USB to FTDI adapter.

The LCD being replaced in an old laptop

Hackaday Prize 2022: Repairing A Vintage Laptop With Modern Components

Laptop computers may be ubiquitous today, but there was a time when they were the exclusive preserve of rich businesspeople. Back in the early ’90s, the significant added cost of portability was something that few were willing to pay. As a result, not many laptops from those days survive; for those that do, keeping them running can be quite a challenge due to their compact construction and use of non-standard components.

[Adalbert] ran into these problems when he got his hands on a Toshiba T3200SXC from 1991. As the first laptop ever to feature a color TFT display, it’s very much worth preserving as an historical artifact. Sadly, the original display was no longer working: it only displayed a very faint image and went completely blank soon after. Leaky capacitors then destroyed the power supply board, leaving the laptop completely dead. [Adalbert] then began to ponder his options, which ranged from trying to repair the original components to ripping everything out and turning this into a modern-computer-in-an-old-case project.

In the end he went for an option in between, which we as preservationists can only applaud: he replaced the display with a modern one of the correct size and resolution and built a new custom power supply, keeping the rest of the computer intact as far as possible. [Adalbert] describes the overall process in the video embedded below and goes into lots of detail on his hackaday.io page.

Connecting a modern LCD screen was not as difficult as it might seem: where the old display had an RGB TTL interface with three bits per color, the new one had a very similar system with six bits per color. [Adalbert] made an adapter PCB that simply connected the three bits from the laptop to the highest three bits on the screen. A set of 3D-printed brackets ensured a secure fit of the new screen in the classic case.

The internal power supply module of a laptopFor the power supply [Adalbert] took a similar approach. He designed a PCB with several DC/DC converters that fit easily inside the computer’s case, leaving enough space to add a battery. This made the old Toshiba more portable than it ever was — believe it or not, the original T3200SXC could only be used with a mains connection.

Once the laptop was restored to working order, [Adalbert] added a few finishing touches: a sound card and speakers made it suitable as a gaming platform, and a network card gave it rudimentary online capabilities. The end result is a T3200SXC that looks and feels exactly the way it did when it was new, but with a few added features. That’s a really satisfying result: many classic laptop projects add modern computing hardware, or even completely replace the original contents. You might also want to check out [Adalbert]’s unusual 3D printer based PCB manufacturing technique that he used for the new power supply.

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Dual Power Supply In A Pinch

Recently I needed a dual voltage power supply to test a newly-arrived PCB, but my usual beast of a lab power supply was temporarily at a client’s site. I had a FNIRSI programmable power supply which would have been perfect, but alas, I had only one. While digging around in my junk box I found several USB-C power-delivery “trigger” boards which I bought for an upcoming project. These seemed almost too small for the task at hand, but after a little research I realized they would work quite well.

The ones I had used the Injoinic IP2721 USB-C power delivery chip, commonly used in many of these boards. Mine had been sold pre-configured for certain output voltages, but they were easy to re-jumper to the voltages I needed, +5 VDC  and +20 VDC. The most challenging aspect was physically using them — they are the size of a fingernail. This version had through-hole output pads on 0.1″ centers, so I decided to solder them to the base of a standard MTA pin header. A few crimps later and I was up and running, along with the requisite pair of USB-C cables and power adapters.

For just a few dollars each, these trigger boards are useful to have in your toolbox, both for individual projects and for use in a pinch. We reviewed these modules a couple of years ago, and check out the far more flexible PD Micro that we covered last year.