A Close Look At USB Power

It’s not a stretch to say that most devices these days have settled on USB as their power source of choice. While we imagine you’ll still be running into the occasional wall wart and barrel jack for the foreseeable future, at least we’re getting closer to a unified charging and power delivery technology. But are all USB chargers and cables created equal?

The answer, of course, is no. But the anecdotal information we all have about dud USB gear is just that, which is why [Igor Brkić] wanted to take a more scientific approach. Inspired by the lighting bolt icon the Raspberry Pi will flash on screen when the voltage drops too low, he set out to make a proper examination of various USB chargers and cables to see which ones aren’t carrying their weight.

In the first half of his investigation, [Igor] tests four fairly typical USB chargers with his TENMA 72-13200 electronic load. Two of them were name brand, and the other just cheap clones. He was surprised to find that all of the power supplies not only met their rated specifications, but in most cases, over-performed by a fair amount. For example the Lenovo branded charger that was rated for only 1 A was still putting out a solid 5 V at 1.7 A. Of course there’s no telling what would happen if you ran them that high for hours or days at a time, but it does speak to their short-term burst capability at least.

He then moved onto the USB cables, were things started to fall apart. The three generic cables saw significant voltage drops even at currents as low as 0.1 A, though the name brand cable with 20 AWG power wires did fare a bit better. But by .5 A they were all significantly below 5 V, and at 1 A, forget about it. Pulling anything more than that through these cables is a non-starter, and in general, you’ll need to put at least 5.2 V in if you want to actually run a USB device on the other side.

Admittedly this might not be groundbreaking research, but we appreciate [Igor] taking a scientific approach and tabulating all the information. If you’re still getting low voltage warnings on the Pi after swapping out your cheapo cables, then maybe the problem is actually elsewhere.

New Part Day: Three-dimensional USB Connectors

There’s an old joke that says USB cables do not exist in three-dimensional Euclidian space. Try to plug a USB cable in a socket, and the first try will always be wrong. Flip it, try to plug it in, and that will also be wrong. You will only succeed on the third try, and this is proof that USB connectors exist in higher planes of reality with arcane geometries. The joke is as old as the Pythagoreans, who venerated USB connectors as gods.

The waveform has collapsed, the gods profaned, and USB connectors that exist in only three dimensions have arrived. We’re talking, of course, about reversible USB Type A connector that will plug in the first time, every time. No need for electromancy or the “looking on the cable for the USB logo and plugging it in with that side up” method used by tech plebeians.

This discovery came after going through my daily roundup of crowdfunding press releases, eventually landing me on this idiotic project. It’s a USB charge cable that’s supposed to charge your phone twice as fast, despite the fact that charging speed is a function of current, and that’s determined by whatever you’re charging from, not the cable. Terrible idea, but they do have something interesting: a three-dimensional USB connector.

connUSBThe connector isn’t the brand new USB 3.1 Type C connector that will eventually find its way into phones, laptops, wearables of all types. This is your standard Type A USB plug you’ve known and loved for the past eighteen years. The difference here is that the chunky block of plastic that has made the common USB cable non-reversible for so many years is gone. In its place is a tiny strip of plastic that has contacts on both sides. Yes, it took nearly two decades for someone to figure out this would be a marketable idea.

While searching for a source for these three-dimensional USB connectors, the only source I could come up with was Wurth Elektronik, With Farnell/Element14 carrying a selection of connectors, a few available on Digikey, and some available on Mouser. There are even a few pre-made reversible cables available, with Tripp Lite leading the game right now.

For integrating one of these connectors into your build, there’s only one thing to watch out for: the pinout for these plugs is mirrored on each side of the thin strip of plastic going down the middle of the connector. This means your VCC and GND pins will be right next to each other, your D+ and D- signal pins right next to each other, and now you have to do your layout with eight pins instead of only four.

While it may not be groundbreaking and it makes for some confusing PCB layout work, but as told by a highly successful crowdfunding campaign, this can be a real feature for a product.

If you’ve recently come across a component, connector, or part that’s unique, interesting, or downright cool everyone should know about, send it on in and we’ll take a look at it.

Hackaday Links Column Banner

Hackaday Links: December 7, 2014

Have some .40 cal shell casings sitting around with nothing to do? How about some bullet earbuds? If you’ve ever wondered about the DIY community over at imgur, the top comment, by a large margin, is, “All of these tools would cost so much more than just buying the headphones”

Here’s something [Lewin] sent in. It’s a USB cable, with a type A connector on one end, and a type A connector on the other end. There is no circuitry anywhere in this cable. This is prohibited by the USB Implementors Forum, so if you have any idea what this thing is for, drop a note in the comments.

Attention interesting people in Boston. There’s a lecture series this Tuesday on Artificial Consciousness and Revolutionizing Medical Device Design. This is part two in a series that Hackaday writer [Gregory L. Charvat] has been working with. Talks include mixed signal ASIC design, and artificial consciousness as a state of matter. Free event, open bar, and you get to meet (other) interesting people.

Ghostbusters. It’s the 30th anniversary, and to celebrate the event [Luca] is making a custom collectors edition with the BluRay and something very special: the Lego ECTO-1.

Let’s say you need to store the number of days in each month in a program somewhere. You could look it up in the Time Zone Database, but that’s far too easy. How about a lookup table, or just a freakin’ array with 12 entries? What is this, amateur hour? No, the proper way of remembering the number of days in each month is some bizarre piece-wise function. It is: f(x) = 28 + (x + ⌊x8⌋) mod 2 + 2 mod x + 2 ⌊1x⌋. At least the comments are interesting.

Arduinos were sold in the 70s! Shocking, yes, but don’t worry, time travel was involved. Here’s a still from Predestination, in theatres Jan 9, rated R, hail corporate.