Solving The Mysteries Of Grounding While Improving A Power Supply

February 4, 2020 by Bryan Cockfield 22 Comments

Grounding problems and unwanted noise in electrical systems can often lead to insanity. It can seem like there’s no method to the madness when an electrical “gremlin” caused by one of these things pops its head out. When looking more closely, however, these issues have a way of becoming more obvious. In a recent video, [Fesz Electronics] shows us how to investigate some of these problems by looking at a small desktop power supply, modelling it in LTSpice, and reducing the noise on the power supply’s output.

While everything in this setup is properly grounded, including the power supply and oscilloscope, the way the grounding systems interact can contribute to the high amount of noise. This was discovered by isolating the power supply from earth ground using electrical tape (not recommended as a long-term solution) and seeing that the noise was reduced. However, the ripple increased substantially, so a more permanent fix was needed. For that, the power supply was modelled in LTSpice. This is where a key discovery was made: since all the parts of the power supply aren’t ideal, noise can be introduced from the actual real-life electrical behavior of some of the parts. In this case, it was non-ideal capacitance in the transformer.

According to the model, this power supply could be improved by adding a larger capacitor across the output leads, and also by increasing their inductance. A large capacitor was soldered in the power supply and an iron ferrule was added, which decreased the noise level from 100 mV to around 20. Still not perfect, but a much needed improvement to the simple power supply. If, on the other hand, you want to make sure you eliminate that transformer’s capacitance completely, you can always go with a transformerless power supply. That carries other risks, though.

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Peek Inside These Same-But-Different Power Supplies

December 28, 2019 by Donald Papp 5 Comments

When [Kerry Wong] found an Amrel PPS 35-2 Programmable Power Supply from the late 90s on eBay, he recognized it as the single-channel version of another unit he owned, the dual-channel Amrel PPS-2322. Naturally, he purchased it and did a compare and contrast of the two models.

From the outside, they look fairly different but weigh about the same. But the similarities on the inside make it quite clear that they share a common design. There are a few things that grab your eye and the 35-2 doesn’t seem quite as well thought out, with some components being soldered into awkward-looking places. Capacitors bristle like barnacles where they are soldered directly to a connector, and a blob of hot glue anchors two resistors that rise up out of the board like a couple of weeds.

The link above shows some high resolution side-by-side photos between the two models, and [Kerry] thoughtfully provides a link to the manual for the PPS series as well as a dump of the firmware (.zip) for the 35-2. A teardown video is embedded below.

Benchtop power supplies are important tools, but we’ve also seen how modern breadboard power supplies are remarkably full-featured.

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Restoring A Dead Commodore 128DCR

December 4, 2019 by Tom Nardi 11 Comments

Another day, another retro computer lovingly restored to like-new condition by [Drygol]. This time, the subject of his attention is a Commodore 128DCR that earned every bit of the “For Parts, Not Working” condition it was listed under. From a spider infestation to a cracked power supply PCB, this computer was in quite a state. But in the end he got the three decade old machine back in working condition and even managed to teach it a few new tricks along the way.

Obviously the shattered PSU was the most pressing issue with the Commodore. Interestingly, the machine still had its warranty seal in place on the back, so whatever happened to this PSU seems to have occurred without human intervention.

Rather than just replacing the PSU, [Drygol] first pieced the board back together with the help of cyanoacrylate glue, and then coated the top with an epoxy resin to give it some mechanical strength. On the back side the traces were either repaired or replaced entirely with jumper wires where the damage was too severe.

With the PSU repaired and tested, he moved on to cleaning the computer’s main board and whitening all the plastic external components. Even the individual keycaps took a bath to get them looking like new again. This put the computer in about as close to like-new condition as it could get.

But why stop there? He next installed the JiffyDOS modification to improve system performance, and wired in an adapter that lets the computer output a crisp 80 columns over S-Video. It’s safe to say this particular Commodore is in better shape now than it was when it rolled off the assembly line.

While an impressive enough final result, this is still fairly tame for [Drygol]. If you want to see a real challenge, take a look at the insane amount of work that went into recreating this smashed Atari 800XL case.

ATX2AT Makes Retrocomputing Safer, Heads To Kickstarter

November 25, 2019 by Donald Papp 21 Comments

It’s easy to take power supplies for granted in modern computing, but powering vintage hardware is not always so simple or worry-free. The power supplies for old electronics are themselves vintage, and the hardware being powered can be quite precious. A power problem can easily cause fried components and burned traces on a board. As [Doc TB] observes, by the time you hear crackling, it’s already far too late.

To address this, [Doc TB] designed the ATX2AT Smart Converter as an open source project and recently decided to make it available through a Kickstarter campaign. ATX2AT is a way to safely and securely replace some vintage power supplies with a standard PC ATX power supply, and adds a large number of protection features such as current monitoring and programmable reaction time for overcurrent protection. All of this can help prevent a retrocomputer enthusiast’s precious vintage hardware from being damaged in the event of a problem. It’s not just for powering known-good hardware; it can be invaluable when testing or repairing hardware that might be in an unknown state.

When we first came across [Doc TB]’s ATX2AT project we recognized it as a well-made device to address a specific niche, and to do it well. Assessing risk takes into account not only the probability of a problem occurring, but also just how bad things would be if it did happen. If your old hardware is precious enough to warrant the extra protection, or you are into repairing or assessing old hardware, then an ATX2AT might be just what you need. You can see it in action in the video embedded below.

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USB Power Delivery For All The Things

October 18, 2019 by Tom Nardi 25 Comments

The promise of USB Power Delivery (USB-PD) is that we’ll eventually be able to power all our gadgets, at least the ones that draw less than 100 watts anyway, with just one adapter. Considering most of us are the proud owners of a box filled with assorted AC/DC adapters in all shapes and sizes, it’s certainly a very appealing prospect. But [Mansour Behabadi] hasn’t exactly been thrilled with the rate at which his sundry electronic devices have been jumping on the USB-PD bandwagon, so he decided to do something about it.

[Mansour] wanted a simple way to charge his laptop (and anything else he could think of) with USB-PD over USB-C, but none of the existing options on the market was quite what he wanted. He looked around and eventually discovered the STUSB4500, a a USB power delivery controller chip that can be configured over I2C.

With a bit of nonvolatile memory onboard, it can retain its settings so he didn’t have to include a microcontroller in his design: just program it once and it can be used stand-alone to negotiate the appropriate voltage and current requirements when its plugged in.

The board that [Mansour] came up with is a handy way of powering your projects via USB-C without having to reinvent the wheel. Using the PC configuration tool and an Arduino to talk to the STUSB4500 over I2C, the board can be configured to deliver from 5 to 20 VDC to whatever device you connect to it. The chip is even capable of storing three seperate Power Delivery Output (PDO) configurations at once, so you can give it multiple voltage and current ranges to try and negotiate for.

In the past we’ve seen a somewhat similar project that used USB-PD to charge lithium polymer batteries. It certainly isn’t happening overnight, but it looks like we’re finally starting to see some real movement towards making USB-C the standard.

Hacking The IKEA TRÅDFRI LED Power Supply

October 8, 2019 by Donald Papp 22 Comments

Just because something is being actively documented and tampered with by enthusiastic hackers doesn’t mean the information is handily centralized. There can be a lot of value in gathering disparate resources in one place, and that’s exactly what [Trammell Hudson] has done with his resource page for hacking the IKEA TRÅDFRI LED power supply with wireless interface. Schematic teardown, custom firmware images, it’s all there in one convenient spot.

Back in 2017, the IKEA TRÅDFRI hacking scene was centered around the LED light bulbs but as the group of products expanded, the rest of the offerings have also gotten some attention.

Why bother tampering with these units? One reason is to add features, but another is to make them communicate over your own MQTT network. And MQTT is the reason you are only a Raspberry Pi and a trip to IKEA away from the beginnings of a smart home that is under no one’s control or influence but your own.

Atomic Pi Gets A 3D-Printed Mac Makeover

September 15, 2019 by Tom Nardi 6 Comments

The Atomic Pi is a pretty impressive piece of kit for the price, but it’s not exactly a turn-key kind of product. Even to a greater extent than what you might normally expect with a “dev” board like this, the user is responsible for putting together the rest of the pieces required to actually utilize it. But with this design by [Renri Nakano], you can turn the Atomic Pi into something that’s dangerously close to being a practical computer, and a trendy one at that.

Inspired by the 2019 Apple Mac Pro “Cheese Grater”, this 3D printable enclosure for the Atomic Pi is equal parts form and function. It integrates the necessary power supply to get things up and running without the need for the official breakout board or power module, which is good, since at the time of this writing they don’t seem to be available anyway. Plus it has a cool looking power button, so that’s got to count for something.

There’s also an integrated USB hub to give the Atomic Pi a bit more expandability, and a short HDMI extension cable that puts a video port on the back of the case. [Renri] even thought to leave an opening so you could run the wires for your wireless antennas.

At this point, we’ve seen several projects that mimic the unique case design of the 2019 Mac Pro. The level commitment ranges from recreating the design in CAD and milling it out of aluminum to just sticking a Raspberry Pi inside of a literal cheese grater from the kitchen. Naturally we enjoy a well executed Internet meme as much as the next hacker, but all the same, we were glad to see [Renri] put in the effort to make sure this case was more than just a pretty face.

[Thanks to baldpower for the tip.]