When we met our contact from MNT in the coffee shop, he was quietly working away on his laptop. Jet black and standing thick it was like an encyclopedia that didn’t quite blend in with the sea of silver MacBook lookalikes on the surrounding tables. After going through all the speeds and feeds we eagerly got our 64 piece driver kit out to open it up and see what made this marvel tick, but when the laptop was turned over it became clear that no tools were needed. The entire bottom of the machine was a single rectangle of transparent acrylic revealing everything from sharp white status LEDs on the bare mainboard to individual 18650 LiFePO4 battery cells in a tidy row. In a sense that’s the summary of the entire product: it’s a real laptop you can use to get work done, and every element of it from design to fabrication is completely transparent.
The MNT Reform
The device pictured here is called the Reform and is designed and manufactured by MNT, a company in Berlin, Germany (note MNT stands for MNT, it’s not an acronym). The Reform is a fully open source laptop which is shipping today and available via distribution through Crowd Supply. If the aesthetic doesn’t make it clear the Reform is an opinionated product designed from the ground up to optimize for free-as-in-freedom: from it’s solid metal chassis to the blob-free GNU/Linux distribution running inside.
We’re here to tell you that we’ve held one, it’s real, and it’s very well built.
[Petteri Aimonen] presents for us a modular differential probe, as his entry into the 2021 Hackaday Prize.
This project shows a simple and well polished implementation of a differential-to-single-ended preamplifier, which allows a differential signal to be probed and fed to an oscilloscope via a BNC cable.
PCB Spark gap for primary ESD protection
It implements a classic instrumentation amplifier, where we have two amplifier stages. The first gives us the options for a gain of either 1 or 10, if we need it, with the second stage having a gain of 2.
The remaining circuit is a power supply to generate the necessary dual-rail supplies to feed the opamps. There is a lot of filtering on those output rails as well as on the USB power input side to try keep all that switched-mode power supply noise out of the signal path.
There are a couple of interesting design choices including the use of PCB material for the long removable probe arms, that integrate PCB spark gaps to offer a first defence against ESD reaching the more delicate parts of the system.
Why This Is Useful
There are two main classes of signals we electronics engineers care about: single-ended and differential-mode.
With the first kind, the signal is carried on a single wire, which is defined as being referenced to the common system ground. Current flows along the wire and returns to its source along the path of least resistance, at least at low frequencies. At higher frequencies, the path of least inductance is more relevant. This is all well and good, so long as you design the PCB correctly.
Coupling from adjacent wires due to mutual capacitance and inductance, as well as noise in the reference ground all conspire to mangle the signal we want to pass down the wire.
As the frequencies increase, and especially if you’re dealing with sharp edges, with all that extra odd-harmonic power, things start to get bad real fast. The way we deal with this is by utilising differential-mode signalling. This is where instead of a single wire, referenced to some notion of ground, we send the signal down a pair of wires, where the voltage difference between the wires forms the signal. Any external noise that leaks into the pair, will (hopefully!) affect both wires equally, forming what we call a common-mode component. When you look at the difference, this common mode noise disappears. (Our own [Bil Herd] covered this some time ago.)
When probing a circuit, it pays to have the right kind of probe as well as an understanding of the effect the probe will have on the circuit in operation. If you have a single-ended signal and you want to view it on your scope, your choice is either a passive or active probe. Usually some kind of passive probe will be most available. These commonly come in 50 Ω and 1 MΩ versions, and you need to be careful to use the correct probe type for your application.
For probing differential signals, it is possible to use a pair of probes, one for each signal wire, and then utilise the scope’s math difference function to show the signal. This is quite often a desperate measure, and what you really want is a differential front-end in hardware. You need a differential active probe.
The circuit may be simple, but don’t underestimate how much tweaking it needs to have good performance – a little slip with the PCB layout, as the author describes, caused some annoying resonances which can be hard to track down.
The project is still under active development, with the author showing the process as the project progresses, but its looking pretty good already, if you ask us.
Sources can found on his GitHib, which uses all Open Source tools, so its pretty accessible too.
There was an urban legend back in the days of mechanical electricity meters, that there were “lucky” appliances that once plugged in would make the meter go backwards. It probably has its origin in the interaction between a strongly capacitive load and the inductance of the coils in the meter but remains largely apocryphal for the average home user. That’s not to say that a meter can’t be fooled into doing strange things though, as a team at the University of Twente have demonstrated by sending some more modern meters running backwards. How have they performed this miracle? Electromagnetic interference from a dimmer switch.
Reading the paper (PDF link) it becomes apparent that this behavior is the result of the dimmer switch having the ability to move the phase of the current pulse with respect to the voltage cycle. AC dimmers are old hat in 2021, but for those unfamiliar with their operation they work by switching themselves on only for a portion of the mains cycle. The cycle time is varied by the dimming control. Thus the time between the mains zero-crossing point and their turn-on point is equivalent to a phase shift of the current waveform. Since electricity meters depend heavily upon this phase relationship, their performance can be tuned. Perhaps European stores will now brace themselves for a run on dimmer switches.
We love depth-sensing cameras and every neat hack they enabled, but this technological novelty has yet to break through to high volume commercial success. So it was sad but not surprising when CRN reported that Intel has decided to wind down their RealSense product line.
As of this writing, one of the better confirmations for this report can be found on the RealSense SDK GitHub repository README. The good news is that core depth-sensing RealSense products will continue business as usual for the foreseeable future, balanced by the bad news that some interesting offshoots (facial authentication, motion tracking) will be declared “End of Life” immediately and phased out over the next six months.
This information tells us while those living out on the bleeding edge will have to scramble, there is no immediate crisis for everyone else, whether they be researchers, hobbyists, or product planners. But this also means there will be no future RealSense cameras, kicking off many “What’s Next?” discussions in various communities. Like this thread on ROS (Robot Operating System) Discourse.
Three popular alternatives offer distinctly different tradeoffs. The “Been Around The Block” name is Occipital, with their more expensive Structure Pro sensor. The “Old Name, New Face” option is Microsoft Azure Kinect, the latest non-gaming-focused successor to the gaming peripheral that started it all. And let’s not forget OAK-D as the “New Kid On The Block” that started with a crowdfunding campaign and building an user community by doing things like holding contests. Each of these will appeal to a different niche, and we’ll keep our eye open in the future. Let’s see if any of them find the success that eluded the original Kinect, Google’s Tango, and now Intel’s RealSense.
Hackaday Prize 2021 entry FlowIO Platform promises to be to pneumatics what Arduino is to Electronics. The modular platform comprises a common controller/valve block, a selection of differently sized pumps, and a few optional connectivity and sensing blocks. With Arduino software support as well as as Javascript and web-GUI, there’s a way to program this no matter what the level of experience the user has.
This last point is a critical one for the mission [Ali Shtarbanov] from the MIT Media Lab is setting out for this project. He reminds us that in decades gone by, there was a significant barrier to entry for anyone building electronics prototypes. Information about how to get started was also much harder to by before the internet really got into gear.
It’s a similar story for software, with tools like Scratch and Python lowering the barrier to entry and allowing more people to get their toes wet and build some confidence.
But despite some earlier work by projects like the Soft Robotics Toolkit and Programmable-Air, making a start on lowering the bar for pneumatics support for soft robotics, and related applications, the project author still finds areas for further improvement. FlowIO was designed from the ground-up to be wearable. It appears to be much smaller, more portable and supports more air ports and a greater array of sensing and connectivity than previous Open Source work to date.
Creative Commons Hardware
Whilst you can take all the plans (free account signup required) and build yourself a FlowIO rig of your very own, the project author offers another solution. Following on from the Wikipedia model of free sharing and distribution of information, FlowIO offers its hardware for free, for the common good. Supported by donations to the project, more hardware is produced and distributed to those who need it. The only ask is that redundant kits are passed on or returned to base for upgrade, rather than landfill.
An SMU or Source Measurement Unit works a bit like a power supply, in that it can source current into a load and a bit like an electronic load, in that it can sink current from a power source. It includes a crossover circuit, so that it cleanly and predictably swaps between sink and source modes automatically. This makes it terribly useful for testing all manner of power circuits, charging and characterizing batteries or just saving bench space by replacing two separate boxes.
This DIY-SMU from analog electronics guru [Dave Erikson] is a full four-quadrant design, meaning that it can operate with both positive and negative voltages. The design shows excellent performance, comparable to commercial instruments that cost serious money, which is testament to [Dave]’s skill and experience.
Source: Wikipedia
The quadrants can be understood if you imagine a graph with voltage on the horizontal axis, and current on the vertical. Both axes can swing to both polarities, with quadrants I & III indicating power delivered into a load and quadrants II & IV power absorbed from a source.
The very detailed project logs show every gory detail, every problem found and the work to solve it. Its a long read, which for those interested in such devices, will be time well spent in this scribe’s humble opinion.
The DIY-SMU is mostly analog in nature, with the control portion courtesy of a Teensy 3.2, with a Nextion TFT display with touch for the user interface. The firmware even supports SCPI over USB to allow remote control and data gathering, so its ready to drop right into your test and measurement stack. For more reading goodness, checkout JSMU, a related project, taking inspiration from the DIY-SMU. Details can be found on this project GitHub repo.
Many power supply projects have graced these pages over the years, like this 2015 Hackaday Prize Entry but this is one of the few four-quadrant designs to be found, so hats off!
Steam branding is strong. Valve Corporation has turned their third-party marketplace into the first place millions choose to buy their PC games. The service has seen record-breaking numbers earlier this year with over 25 million concurrent users, so whatever they are doing is clearly working. Yet with all those software sales, last month Valve announced a new piece of hardware they call the Steam Deck.
Use the colloquialism you’d like, “not resting on your laurels” or “Mamba Mentality”, it’s not as if competitors in the handheld PC space are boasting ludicrous sales numbers. At their core, Valve is in the business of selling computer games. So why venture into making hardware? Continue reading “Valve Sells Software, So What’s With All The Hardware?”→
