Bench Supplies Get Smaller Thanks To USB-C

October 19, 2020 by Bryan Cockfield 17 Comments

Bench power supplies are an indispensable tool when prototyping electronics. Being able to set custom voltages and having some sort of current limiting feature are key to making sure that the smoke stays inside all of the parts. Buying a modern bench supply might be a little too expensive though, and converting an ATX power supply can be janky and unreliable. Thanks to the miracle of USB-C, though, you can build your own fully-featured benchtop power supply like [Brian] did without taking up hardly any space, and for only around $12.

USB-C can be used to deliver up to 100W but is limited to a few set voltage levels. For voltages that USB-C doesn’t support, [Brian] turns to an inexpensive ZK-4KX buck-boost DC-DC converter that allows for millivolt-level precision for his supply’s output. Another key aspect of using USB-C is making sure that your power supply can correctly negotiate for the amount of power that it needs. There’s an electronic handshake that goes on over the USB connection, and without it there’s not a useful amount of power that can be delivered. This build includes a small chip for performing this negotiation as well.

With all the electronics taken care of, [Brian] houses all of this in a 3D-printed enclosure complete with a set of banana plugs. While it may not be able to provide the wattage of a modern production unit, for most smaller use cases this would work perfectly. If you already have an ATX supply around, though, you can modify [Brian]’s build using that as the supply and case too.

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USB-C Where It Was Never Intended To Be

July 24, 2020 by Jenny List 25 Comments

The USB-C revolution is well under way, as first your new phone, then your single-board computer, and now your laptop are likely so sport the familiar reversible round-cornered connector. We’re still in the crossover period of requiring to keep micro USB, proprietary laptop, and USB-C power supplies at hand, but the promise of a USB-C-only world is tantalisingly close. For [Purkkaviritys] that’s a little bit closer now, as he’s modified his Thinkpad T440s to take a USB charger instead of its proprietary Lenovo square-plug part. (Video, embedded below.)

At its heart is a USB-PD emulator module that does all the hard work of negotiation with the power supply, giving the laptop the DC voltage it needs. It’s not quite that simple though, because a resistor is required to reassure the laptop that it’s got a genuine power supply. The module is encased in a carefully-designed surround that neatly takes the space vacated by the original connector, and since this laptop has its internal power connector on a short cable it is made very straightforward to fit into the case. If you didn’t know it was a home-made upgrade, you could be forgiven for thinking that this laptop left the factory with a USB-C power socket.

The USB-C module used here is a versatile part. We’ve previously seen it in a soldering iron conversion.

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A DIY Electronics Lab You Can Show Off With Pride

May 25, 2020 by Tom Nardi 27 Comments

It’s hardly a secret that getting into a serious electronics habit can be detrimental to your bank account. A professional grade lab is simply unobtainable for many a tinkerer, and even mid-range hardware can set you back considerably. Which is why many folks just starting out will attempt to salvage or build as much of their equipment as possible. It might not always be pretty, but it’ll get the job done.

But this project by [Chrismettal] could end up completely reinventing the home electronic workspace. Using 3D printed frames, low-cost components, and a sprinkling of custom PCBs, this modular electronics workbench has all the bells and whistles an aspiring hardware hacker could need. As an added bonus, it looks like something that came off the International Space Station.

Inside the resistor substitution module.

This is one of those projects that simply can’t be done justice in a few paragraphs. If you’ve ever wanted to put together a dedicated electronics workbench but were put off by the cost of individual components, read though the fantastic documentation [Chrismettal] has prepared for the EleLab_v2. Is it all top-of-the-line hardware? No, of course not. But it’s more than suitable for the kind of work people in this community usually find themselves involved in on a weekend.

So what’s included? Naturally [Chrismettal] has created a power supply module, in both variable and fixed flavors. But there’s also a module for a resistor substitution, a component tester, and even a digital storage oscilloscope. You can mix and match the modules suit your needs, and if you want to create entirely new ones, the FreeCAD sources are available to get you started.

We’ve seen low-cost power supply modules before, and naturally we’re no strangers to cheap DSO kits. But this project wraps those devices and gadgets up into a form factor that anyone would be happy to have on their bench. We’re exceptionally interested in seeing new modules developed for the EleLab_v2, and doubt this is the last time you’ll see this impressive project grace these pages.

[Thanks to BrunoC for the tip.]

Side-Channel Attack Turns Power Supply Into Speakers

May 11, 2020 by Dan Maloney 12 Comments

If you work in a secure facility, the chances are pretty good that any computer there is going to be stripped to the minimum complement of peripherals. After all, the fewer parts that a computer has, the fewer things that can be turned into air-gap breaching transducers, right? So no printers, no cameras, no microphones, and certainly no speakers.

Unfortunately, deleting such peripherals does you little good when [Mordechai Guri] is able to turn a computer power supply into a speaker that can exfiltrate data from air-gapped machines. In an arXiv paper (PDF link), [Guri] describes a side-channel attack of considerable deviousness and some complexity that he calls POWER-SUPPLaY. It’s a two-pronged attack with both a transmitter and receiver exploit needed to pull it off. The transmitter malware, delivered via standard methods, runs on the air-gapped machine, and controls the workload of the CPU. These changes in power usage result in vibrations in the switch-mode power supply common to most PCs, particularly in the transformers and capacitors. The resulting audio frequency signals are picked up by a malware-infected receiver on a smartphone, presumably carried by someone into the vicinity of the air-gapped machine. The data is picked up by the phone’s microphone, buffered, and exfiltrated to the attacker at a later time.

Yes, it’s complicated, requiring two exploits to install all the pieces, but under the right conditions it could be feasible. And who’s to say that the receiver malware couldn’t be replaced with the old potato chip bag exploit? Either way, we’re glad [Mordechai] and his fellow security researchers are out there finding the weak spots and challenging assumptions of what’s safe and what’s vulnerable.

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Go The Extra Mile For Your LED Driver

May 4, 2020 by Kerry Scharfglass 7 Comments

Addressable RGB LED strips may be all the rage, but that addressability can come at a cost. If instead of colors you expect to show shades of white you may the find less flickery, wider spectrum light from a string of single color LEDs and a nice supply desirable. Of course there are many ways to drive such a strip but this is Hackaday, not Aliexpressaday (though we may partake in the sweet nectar of e-commerce). [Niklas Fauth] must have really had an itch to scratch, because to get the smoothest fades for his single color LED strips, he built an entire software defined dual 50W switched-mode AC power supply from scratch. He calls it his “first advanced AC design” and we are suitably impressed.

Switched-mode power supplies are an extremely common way of converting arbitrary incoming AC or DC voltage into a DC source. A typical project might use a fully integrated solution in the form of a drop-in module or wall wart, or a slightly less integrated controller IC and passives. But [Niklas] went all the way and designed his from scratch. Providing control he has the ubiquitous ESP-32 to drive the control nodes of the supply and giving the added bonus of wireless connectivity (one’s blinkenlights must always be orchestrated). We can’t help but notice the PCBA also exposes RS485 and CAN transceivers which seem to be unused so far, perhaps for a future expansion into wired control?

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In-Depth Design Of A Flyback Converter

April 25, 2020 by Jenny List 13 Comments

It is tempting to think of analogue and digital domains as entirely distinct, never to touch each other except like a cold war Checkpoint Charlie, through the medium of an ADC or DAC. In reality there are plenty of analogue effects upon digital circuitry which designers must be aware of, but there is one field in which the analogue and the digital are intricately meshed. Switch mode power supplies use digital techniques to exploit the analogue properties of components such as inductors and capacitors, and can be astoundingly clever in the way they do this to extract the last fraction of a percent efficiency from their conversion. Thus their design can be something of a Dark Art, so it’s always interesting to have a good read explaining some of the intricacies. [James Wilson] has built a flyback step-up converter to power Nixie tubes, and his write-up follows the whole process in great depth.

This type of converter seems at first glance to be a simple step-up design with a transformer that has a primary and secondary, where in fact it relies on the collapse in magnetic field during the off period of its duty cycle to provide a spike in voltage and thus a step-up beyond that you’d expect from the transformer alone. The write-up takes us through all this starting from a theoretical perspective, and then goes further into the realm of component selection and the effects of component properties on the waveforms involved. If you have ever battled ringing in a switch mode power supply you may recognise some of this.

If this field interests you, then there is probably no better place to send you for a start than Jim Williams’ 1987 app note 25 for Linear Technology: “Switching Regulators for Poets“.

Fixing An Agilent Oscilloscope Power Supply

April 18, 2020 by Jenny List 22 Comments

We should all be so lucky as [Salvaged circuitry], who scored a cheap Agilent oscilloscope from an online auction. Of course, its low price had a reason behind it, the ‘scope didn’t work. At fault was its power supply, the repair of which was documented in the video below.

These ‘scopes have relatively straightforward 12 V power supplies, extremely similar to off-the-shelf parts. The video is an interesting primer in switch-mode power supply repair, as the obvious failure of the filter capacitor and a MOSFET is traced further to the PSU controller chip. We see a new capacitor mounted proud of the board to reduce the risk of heat damage, and then some careful solder rework to save some lifted pads.

The result, a working oscilloscope. Maybe we’d have hacked in another 12 V supply, but given that this is a piece of test equipment perhaps it’s best to stay as close to the original spec as possible. As a parting shot he shows us an equivalent power supply, and promises us a side-by-side test in a future video.

These ‘scopes aren’t as popular in our circles as the cheaper Rigol range, but it’s worth remembering that they also have a budget model.

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