an analog CO2 gauge with a cute face

Cute CO2 Gauge Tells You When To Crack A Window

March 19, 2024 by 25 Comments

[Cyrill] has a good home automation scheme going: there are a number of physical switches set around the place that control the essential functions. The only problem is that in the winter time, this results in a great deal of phone checking as [Cyrill] tries to monitor the CO2 level. Tired of all this screen time, [Cyrill] set about to create an incredibly cute (and useful) Co2 monitor that plainly shows the current level and how bad it is, relatively speaking.

A large servo and an ESP32-S2 make up the guts of an analog CO2 sensor.

Behind that adorable face is a DS3225 servo being driven by a Wemos S2 mini, both of which [Cyrill] happened to have handy. Although the 25 Kg servo may be complete overkill for the situation, [Cyrill] reports that it is quieter than your average AliExpress alternatives, which makes it well worth it in our book. Then it was on to Inkscape to make the gauge itself. [Cyrill] says they’re an Inkscape noob, but that face could have fooled us.

Finally, it was time to integrate it into Home Assistant to get readings from the CO2 sensors. This was easier said than done, but [Cyrill] does a nice job of explaining how to get the ESP32-S2 up and working.

If you’re out there monitoring CO levels in your home, beware of fake sensors that cropped up during the height of the pandemic and are likely still at large.

2024 Home Sweet Home Automation: A Piano-Controlled Smart Home

March 19, 2024 by 7 Comments

There’s a scene in Willy Wonka and the Chocolate Factory where a little flap in the wall flips down to reveal a small organ embedded there. Gene Wilder plays a bit of Rachmaninoff on the organ, and the giant door to the chocolate room slowly creaks open.

Once [Nathan Orick] got this into his head, he couldn’t get it out, and had to give it a go in his own home. Regrettably there’s no chocolate rooms in the house, so he’s using various chords and melodies to do things like control the lights and the TV, as you’ll see in the video after the break. Although this one may have started as a joke of a home automation scheme, [Nathan] thinks it turned out pretty solid, and so do we.

He already had the piano and a Raspberry Pi Zero lying around, so getting this up and running was mostly about connections and code. Speaking of connections, [Nathan] was hard-pressed to find a micro-USB to USB-B cord, so he ended up splicing one together. Simple enough. The harder part was getting Linux to recognize the keyboard, but all it took was touching all the pins with a multimeter, evidently. What’s a project without a little magic?

And not only did it show up, Linux went to the trouble of registering it as a MIDI device all on its own. Once [Nathan] obtained the port number, he had data printing to the console every time he played a note. Then it was mostly a matter of writing code to interact with MIDI data and track the notes as they’re played, and put it all together with Home Assistant. Be sure to check out the brief demo after the break.

Continue reading “2024 Home Sweet Home Automation: A Piano-Controlled Smart Home” →

PCB Design Review: ESP32-S3 Round LCD Board

March 19, 2024 by 6 Comments

For our next installment, I have a lovely and daring PCB submitted by one of our readers, [Vas]. This is an ESP32-S3 board that also has an onboard round TFT display, very similar to the one we used on the Vectorscope badge. The badge is self-sufficient – it has an ESP32, it has a display, a programming connector, two different QWIIC ports you could surely use as GPIOs – what’s not to love?

This is a two-layer board, and I have to admit that I seriously enjoy such designs. Managing to put a whole lot of things into two layers is quite cool in my book, and I have great fun doing so whenever I get the opportunity. There’s nothing wrong with taking up more layers than needed – in fact, if you’re concerned about emitted/received noise or you have high-speed interfaces, four-layer is the way to go. But making complex boards with two layers is a nice challenge, and, it does tend to make these boards cheaper to manufacture as a very nice bonus.

Let’s improve upon it, and support [Vas]’s design. From what I can see looking at this board, we can help [Vas] a lot with ease of assembly, perhaps even help save a hefty amount of money if they go for third-party PCBA instead of sitting down with a stencil – which you could do with this board pretty easily, since all of the components on it, save for the display, are the ones you’d expect JLCPCB to stock.

Continue reading “PCB Design Review: ESP32-S3 Round LCD Board” →

Running Power And Data Over Just Two Wires

March 19, 2024 by 50 Comments

When you’re hooking up equipment across a vehicle, you’re often stuck sending power and data to and from things like sensors or actuators. The more wires you have to run, the more hassle, so it’s desirable to get this number as low as possible. That’s an especially big deal in the world of cycling electronics, where every additional gram is considered a drawback. To this end, companies have developed two-wire methods of sending power and data together, and now, [Keith Wakeham] has devised his own way of doing so.

[Keith] was inspired by Shimano’s E-Tube system which is fairly fancy in its encoding schemes, but he went his own way. His concept relied on old-school On-Off Keying methods to take a signal and capacitively couple a signal into power lines. He explains the theory behind the method, and shares schematics that can be used to actually communicate over power lines. Then, he shows off the real hardware that he built to test the concept for himself.

The results? Good! [Keith] was able to maintain speeds of 57,600 bits/second even with an electrically-noisy gear motor operating on the lines. That’s more then enough for all kinds of applications.

If you’ve got your own data-over-powerline hacks, don’t hesitate to let us know. Continue reading “Running Power And Data Over Just Two Wires” →

The Greenhouse Effect Isn’t For Greenhouses

March 19, 2024 by 22 Comments

Think of a greenhouse. It’s a structure with glass walls that lets light in and traps heat, all for the benefit of the plants inside. As for how it works, that’s elementary! It’s all down to the greenhouse effect… right?

Alas, no. So many of us have been mislead. Let’s rexamine how we think greenhouses work, and then explore what’s actually going on.
Continue reading “The Greenhouse Effect Isn’t For Greenhouses” →

Photoresistors Provide Air Gap Data Transfer, Slowly

March 19, 2024 by 50 Comments

One of the simplest ways of keeping a computer system secure is by using an air gap — that is, never actually connecting the system to the network. This can often include other peripherals like USB drives and other removable storage as well, so getting information to and from secure (or compromised) systems behind air gaps can often present a challenge. But assuming you have local access to the computer and your parts bin handy, these optical solutions from [Nikolay] can allow  data transfer to or from such off-line computers.

[Nikolay]’s specific use case for this project is to transfer small amounts of information to or from computers that may be compromised in some way, or computers that might otherwise be dangerous to connect to other equipment. There’s actually several methods described in the project, the first involves temporarily attaching a photoresistor to the computer’s screen which has been wired into the remains of a USB keyboard. A script running on the compromised machine translates data into a series of white and black squares. The sensors can detect these patterns much like playing Duck Hunt on an old CRT television and transmit the data across the air gap with reasonable certainty nothing harmful crossed with it.

Continue reading “Photoresistors Provide Air Gap Data Transfer, Slowly” →

Modern Microcontroller Boosts Classic Logic Analyzer To New Heights

March 19, 2024 by 5 Comments

[Ted Fried] recently found a beautiful HP 1600A/1607A logic analyzer set. State of the art in 1975, it looks like glorious Space Age equipment today. He decided to hook it up some modern gear to put it through its paces.

Wanting to give the equipment a proper shakedown, he enlisted a Teensy 4.1 to spit a deluge of logic at the HP unit. The microcontroller was tasked with generating 32 data signals along with two clock outputs to give the analyzer plenty to analyze. The HP 1600A handled this no problem, so [Ted] kept tinkering.

His next feat was to explore the addressable “MAP” function of the unit, which allowed writing to the 64×64 pixel display. The Teensy 4.1 was easily able to send images to the display, but [Ted] isn’t stopping there. He’s got plans to do the usual thing and get Bad Apple going on the hardware.

Getting a logic analyzer to analyze logic isn’t much of a hack, sure. But it’s instructive of how to approach working with such hardware. If you want to spit a bunch of logic out fast, a Teensy 4.1 is a great choice because it’s got a ton of IO and a ton of clock cycles to tickle it with.

We enjoyed seeing this old piece of hardware light up the phosphors once more. If you’ve got your own projects going on with classic bits of HP test gear, don’t hesitate to let us know!