The Joy Of Properly Designed Embedded Systems

March 20, 2019 by Maya Posch 32 Comments

The ages-old dream of home automation has never been nearer to reality. Creating an Internet of Things device or even a building-wide collection of networked embedded devices is “easy” thanks to cheap building blocks like the ESP8266 WiFi-enabled microcontroller. Yet for any sizable project, it really helps to have a plan before getting started. But even more importantly, if your plan is subject to change as you work along, it is important to plan for flexibility. Practically, this is going to mean expansion headers and over-the-air (OTA) firmware upgrades are a must.

I’d like to illustrate this using a project I got involved in a few years ago, called BMaC, which grew in complexity and scope practically every month. This had us scrambling to keep up with the changes, while teaching us valuable lessons about how to save time and money by having an adaptable system architecture.

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Whirling Sawblades Turn Foam Packaging Into Wall Insulation

March 19, 2019 by Dan Maloney 60 Comments

If you’re like us, the expanded polystyrene (EPS) foam inserts that protect many packages these days are a source of mixed feeling. On the one hand, we’re glad that stuff arrives intact thanks to the molded foam inserts. But it seems so wasteful, especially when chucking it in the garbage can. If only it could be effectively recycled.

It turns out that it can be, if you equip yourself with this spinning “sawblades of doom” EPS recycler. It comes by way of [HowToLou], who was looking for a way to insulate a wall on the cheap. Almost all commercially available insulating materials – fiberglass batts, blown-in cellulose, expanding polyisocyanurate – are pretty pricey. Foam packing pieces are pretty easy to come by, though, and usually free for the taking. [Lou]’s method of turning them into insulation is a box containing four circular saw blades mounted to a piece of threaded rod and spun by a cordless drill. The blades are mounted askew on the rod for better reduction of the foam; [Lou] chose to use wire to hold the blades down, while we’d have printed up some slanted arbors and bolted the blades down more firmly. A chicken wire prefilter keeps the big chunks from clogging a blower made from an old bathroom exhaust fan, which does a great job of filling the wall cavities with pulverized EPS nuggets. The video below has all the details.

Honestly, the box is a little scary, and we have doubts that [Lou] will be able to get enough foam to finish the job, but it’s still a clever little hack. Grinding things up seems to be a theme for him; check out his leaf collector or his apple cider press.

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The Heat Is On With This ESP8266 Controlled Sauna

March 8, 2019 by Tom Nardi 14 Comments

We’ll be perfectly honest: sitting inside a heated box sounds just a bit too much like torture for our tastes. But if we did somehow find ourselves in possession of a fancy new sauna, we’d more than likely follow in the footsteps of [Al Betschart] and make the thing controllable with the ESP8266. After all, if you’re going to be cooked alive, you might as well do it on your own terms.

The sauna itself was purchased as a kit, and included an electric heater controlled by a thermostat. As explained in his detailed documentation, [Al] integrated a Sonoff TH16 into the original heater circuit so he could control power to the coils remotely. The TH16 also includes support for a thermal sensor, which allowed him to get a reading on the sauna’s internal temperature. The new electronics were mounted in a weather-proof box on the back of the sauna, complete with an external WiFi antenna to help get a good signal back to the house.

At this point the project could technically be done if all you wanted was remote control, but [Al] wanted to create a replacement firmware for the Sonoff that was specifically geared towards the sauna. So he came up with some code that uses MQTT to connect the heater to his home automation system, and allows configuring things like the maximum temperature and how long the sauna will run before turning itself off.

Interestingly, the company who makes these saunas thought the work [Al] did to integrate their product into his home automation system was so impressive they actually interviewed him about it and put it up on their site for others who might be inspired by his work. We’ve covered a lot of hacks to consumer devices here at Hackaday, and it’s exceedingly rare for a company to be so supportive of customers fiddling around with their products (especially in a case like this where there’s a real chance of burning your house down), so credit where credit is due.

The last time we brought you a sauna hack it was quite literally in a van down by the river, so the addition of an ESP8266 certainly brings this more into our comfort zone. Figuratively, if not literally.

[Thanks to Jon for the tip.]

Forget The Kiln, These Tiles Were Made On A Prusa

March 5, 2019 by Tom Nardi 22 Comments

Where does your mind go when you think of 3D printed parts? Running off hard to find replacement components? Maybe spinning up a bespoke electronics enclosure? Occasionally the little boat that you can compare to the little boats of others online? All reasonable enough answers. But thanks to the work of [Matthew Wentworth], you might have a new mental image to associate with the smell of melting PLA: decorative Portuguese Azulejo tiles.

As difficult as it might be to believe, the tiles you’re seeing here weren’t made on some exotic ceramic printer, but a standard Prusa i3 MK3. Well, at least they started on the 3D printer. As you might have guessed, there’s a bit more involved than that.

That said, the idea is actually quite simple. The printed “tile” is just the base plate, plus the raised elements that will eventually be seen on the surface. Everything else is just a void, which naturally saves a lot on printing time and material. Once the print is done, premixed spackling paste is pushed into all of the open areas and the top is made as smooth as possible with a putty knife. The filled tile is then left to dry for 24 hours or so.

Once it’s dried, you take the tile outside and sand the top down with a palm sander (or by hand, if you have the patience). This not only smooths out the spackle, but eventually will expose and then smooth the top parts of the print. Once everything is nice and silky, it gets sprayed with a semi-gloss clear coat to both protect it and give it that authentic looking shine.

[Matthew] actually created his designs based on images of real Azulejo tiles he found online, but really any sort of image that has raised elements like this could be made to work. If anyone out there decorates their home with 3D printed Jolly Wrencher tiles, you know where to send the pictures. Interestingly, these aren’t the first tiles we’ve seen made out of plastic, but we’ve got to admit these ones would look quite a bit more appealing on your kitchen walls.

Hack My House: Raspberry Pi As A Touchscreen Thermostat

February 27, 2019 by Jonathan Bennett 51 Comments

Your thermostat is some of the oldest and simplest automation in your home. For years these were one-temperature setting and nothing more. Programmable thermostats brought more control; they’re alarm clocks attached to your furnace. Then Nest came along and added beautiful design and “learning features” that felt like magic compared to the old systems. But we can have a lot more fun. I’m taking my favorite single-board computer, the Raspberry Pi, and naming it keeper of heat (and cool) by building my own touchscreen thermostat.

Mercury thermostats started it all, and were ingenious in their simplicity — a glass capsule containing mercury, attached to a wound bi-metal strip. As the temperature changes, the contraption tilts and the mercury bead moves, making or breaking contact with the wiring. More sophisticated thermostats have replaced the mercury bead with electronics, but the signaling method remains the same, just a simple contact switch.

This makes the thermostat the prime target for an aspiring home automation hacker. I’ve had this particular project in mind for quite some time, and was excited to dive into it with simple raw materials: my Raspberry Pi, a touchscreen, and a mechanical relay board.

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A Modern Solution To Tea Bag Inventory Management

February 20, 2019 by Lewin Day 13 Comments

Britain is famously known as a land of manners and hospitality. Few situations could make an Englishman’s stiff upper lip quiver, short of running out of tea bags while entertaining house guests. Thankfully, [The Gentleman Maker] is here and living up to his name – with a helpful tea monitor to ensure you’re never caught out again.

The Intelli-T, as it has been dubbed, monitors tea inventory by weight. An Arduino Uno combined with a HX711 IC monitors a load cell mounted under a canister, with a reed switch on the lid. Upon the canister being open and closed, the Arduino takes a measurement, determining whether tea stocks have dipped below critical levels. If the situation is dire, a Raspberry Pi connected over the serial port will sound an urgent warning to the occupants of the home. If there is adequate tea, the Raspberry Pi will instead provide a helpful tea fact to further educate the users about the hallowed beverage.

It’s a fun project, and one that has scope for further features, given the power of the Raspberry Pi. A little more work could arrange automatic ordering of more tea online, or send alerts through a service like IFTTT. We’ve seen [The Gentleman Maker]’s uniquely British hacks before, such as the umbrella that tells you the weather. Video after the break.

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Hack My House: Garage Door Cryptography Meets Raspberry Pi

February 13, 2019 by Jonathan Bennett 57 Comments

Today’s story is one of victory and defeat, of mystery and adventure… It’s time to automate the garage door. Connecting the garage door to the internet was a must on my list of smart home features. Our opener has internet connection capabilities built-in. As you might guess, I’m very skeptical of connecting a device to the internet when I have no control over the software running on it.

The garage door is controlled by a button hung on the garage wall. There is only a pair of wires, so a simple relay should be all that is needed to simulate the button press from a Raspberry Pi. I wired a relay module to a GPIO on the Pi mounted in the garage ceiling, and wrote a quick and dirty test program in Python. Sure enough, the little relay was clicking happily– but the garage door wasn’t budging. Time to troubleshoot. Does the push button still work? *raises the garage door* yep. How about the relay now? *click…click* nope.

You may have figured out by now, but this garage door opener isn’t just a simple momentary contact push button. Yes, that’s a microcontroller, in a garage door button. This sort of scenario calls for forensic equipment more capable than a simple multimeter, and so I turned to Amazon for a USB oscilloscope that could do some limited signal analysis. A device with Linux support was a must, and Pico Technology fit the bill nicely.

Searching for a Secret We Don’t Actually Need

My 2 channel Picotech oscilloscope, the 2204A, finally arrived, and it was time to see what sort of alien technology was in this garage door opener. There are two leads to the button, a ground and a five volt line. When the button is pressed, the microcontroller sends data back over that line by pulling the 5 V line to ground. If this isn’t an implementation of Dallas 1-wire, it’s a very similar concept.

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