Arduino Powered Heat Pump Controller Helps Warm Your Toes

September 8, 2021 by Dave Rowntree 39 Comments

Heat pump heating technology is starting to pop up more and more lately, as the technology becomes cheaper and public awareness and acceptance improves. Touted as a greener residential heating system, they are rapidly gaining popularity, at least in part due to various government green policies and tax breaks.

[Gonzho] has been busy the last few years working on his own Arduino Powered Open Source heat pump controller, and the project logs show some nice details of what it takes to start experimenting with heat pumps in general, if that’s your game. Or you could use this to give an old system a new lease of life with an Arduino brain transplant.

In essence they are very simple devices; some kind of refrigerant is passed through a source of heat, absorbing some of it, it then flows elsewhere, and is compressed, which increases its temperature, before that increased heat is lost where the increase in temperature is desired.

This heat source could be a river, a mass of pipes buried in the ground, or simply the air around you. The source and quality of the heat source as well as the desired system operating temperature dictate the overall efficiency, and with ground-source systems it’s even possible to dump excess heat directly into the ground and store it for when required later. This could be the result of a residential cooling system, or even directly sourced from a solar heated setup.

This heat pumping process is reversible, so it is possible to swap the hot and cold ends, just by flipping some valves, and turn your space heater into a space cooler. This whole process can trace its roots back to the super talented Scottish professor, William Cullen who in 1748 was the first person on record to demonstrate artificial refrigeration.

The power needed to run the compressor pump and control gear is usually electrically derived, at least in non-vehicular applications, but the total power required is significantly less than the effective heating (or cooling) power that results.

We’ve covered a few heat pump hacks before, like this guy who’s been heating his house geothermally for years, but not so many platforms designed for experimentation from the ground up.

The associated GitHub project provides the gerber files as well as the Arduino code, so you’ve got a great starting point for your own heat pumping builds.

100% display from filter screen and the responsible mod chip

Clearing The Air About Proprietary Consumables With A Xiaomi Filter DRM Resetter

August 28, 2021 by Brian McEvoy 16 Comments

The “razor and blades model” probably set a lot of young hackers on their current trajectory. If we buy a widget, we want to pick our widget refills instead of going back to the manufacturer for their name-brand option. [Flamingo-Tech] was having none of it when they needed a new filter for their Xiaomi air purifier so they set out to fool it into thinking there was a genuine replacement fresh from the box. Unlike a razor handle, the air purifier can refuse to work if it is not happy, so the best option was to make a “mod-chip.”

The manufacturer’s filters have a Near-Field Communication (NFC) chip and antenna which talk to the base station. The controller receives the filter data via I₂C, but the mod-chip replaces that transmitter and reassures the controller that everything is peachy in filter town. On top of the obvious hack here, [Flamingo-Tech] shows us how to extend filter life with inexpensive wraps, so that’s a twofer. You can create your own mod-chip from the open-source files or grab one from [Flamingo-Tech’s] Tindie store.

We usually hear about mod-chips in relation to games, but we are happy to extend that honor to 3D printers. Have you ever fooled a “razor?”

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Hands-On: MNT Reforms The Laptop

August 26, 2021 by Kerry Scharfglass 122 Comments

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.

a view of the inside of a MNT Reform laptop, showing screen and keyboard — 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.

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This Modular Differential Probe Shows Great Attention To Detail

August 25, 2021 by Dave Rowntree 14 Comments

[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.

Electromagnetic Interference For Fun And Profit

August 22, 2021 by Jenny List 24 Comments

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.

If you’re curious about these old-style dimmers, take a look at some of their basic functionality.

Thanks [Dorus] for the tip.

RealSense No Longer Makes Sense For Intel

August 20, 2021 by Roger Cheng 15 Comments

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.

[via Engadget]

Get Your Flex On With The FlowIO Platform

August 20, 2021 by Dave Rowntree 7 Comments

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.

flowIO exploded view from http://www.softrobotics.io/flowio

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.

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