A Guard Bot For Your Home Assistant

While fixed sensors, relays, and cameras can be helpful in monitoring your home, there are still common scenarios you need to physically go and check something. Unfortunately, this is often the case when you’re away from home. To address this challenge, [PriceLessToolkit] created a guardian bot that can be controlled through Home Assistant.

The robot’s body is made from 3D printed components designed to house the various modules neatly. The ESP32 camera module provides WiFi and video capabilities, while the Arduino Pro Mini serves as the bot’s controller. Other peripherals include a light and radar sensor, an LED ring for status display, and a speaker for issuing warnings to potential intruders. The motor controllers are salvaged from two 9-gram servos. The onboard LiPo battery can be charged wirelessly with an integrated charging coil and controller by driving the bot onto a 3D printed dock.

This build is impressive in its design and execution, especially considering how messy it can get when multiple discrete modules are wired together. The rotating caster wheels made from bearings add an elegant touch.

If you’re interested in building your own guard bot, you can find the software, CAD models, and schematics on GitHub. If you’re looking to add other gadgets to your Home Assistant setup, we’ve seen it connect to boilers, blinds, beds and 433 MHz sensors.

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Home Heating With Bitcoin Miners Is Now A Real Thing

If you were reading this post a month ago, you could have been forgiven for thinking it was an April Fools post. But we assure you, this is no joke. A company called HeatBit has recently opened preorders for their second generation of Bitcoin miner that doubles as a space heater.

The logic goes something like this: if you’re going to be using an electric space heater anyway, which essentially generates heat by wasting a bunch of energy with a resistive element, why not replace that element with a Bitcoin miner instead? Or at least, some of the element. The specs listed for the HeatBit Mini note that the miner itself only consumes 300 watts, which is only responsible for a fraction of the device’s total heat output. Most of the thermal work is actually done by a traditional 1000 watt heater built inside the 46 cm (18 inch) tall cylindrical device.

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Reverse Engineering An Oil Burner Comms Board, With A Few Lucky Breaks

Here’s a question for you: How do you reverse engineer a circuit when you don’t even have it in hand? It’s an interesting problem, and it adds a level of difficulty to the already iffy proposition that reverse engineering generally presents. And yet, not only did [themole] find a way to replicate a comms board for his oil burner, he extended and enhanced the circuit for integration into his home automation network.

By way of backstory, [themole] has a wonky Buderus oil burner, which occasionally goes into safety mode and shuts down. With one too many cold showers as a result, he looked for ways to communicate with the burner controller. Luckily, Buderus sells just the thing — a serial port module that plugs into a spare slot in the controller. Unluckily, the board costs a bundle, and that’s even if you can find it. So armed with nothing but photos of the front and back of the board, the finding of which was a true stroke of luck, he set about figuring out the circuit.

With only a dozen components or so and a couple of connectors, the OEM board gave up its secrets pretty easily; it’s really just a level shifter to make the boiler talk RS-232. But that’s a little pass√© these days, and [the78mole] was more interested in a WiFi connection. So his version of the card includes an ESP32 module, which handles wireless duties as well as the logic needed to talk to the burner using the Buderus proprietary protocol. The module plugs right into the burner controller and connects it to ESPHome, so no more cold showers for [themole].

We thought this one was pretty cool, especially the way [themole] used the online photos of the board to not only trace the circuit but to get accurate — mostly — measurements of the board using an online measuring tool. That’s a tip we’ll keep in our back pocket.

Thanks to [Jieffe] for the tip.

Tiny Microcontroller Uses Real-Time Operating System

Most of the computers we interact with on a day-to-day basis use an operating system designed for flexibility. While these are great tools for getting work done or scrolling your favorite sites, they have a weakness when it comes to interacting quickly with a real-world environment. For these kinds of low-latency, high-reliability systems you may want to turn to something like freeRTOS which is optimized for this kind of application and which [Parikshit Pagare] has used to build his home automation system.

This build is based around an ESP32 for which freeRTOS, designed specifically for embedded systems, is uniquely suited. There are several channels built in capable of monitoring temperature, functioning as a smoke alarm, and sensing whether someone is at the front door. All of these are reported to a small OLED screen but are also updated on an Android app as well, which happens nearly instantaneously thanks to the real-time operating system. There are a number of user-controllable switches as well that are capable of turning lights or fans on and off.

For a home automation system, it’s one of the most low-cost and fully-featured we’ve seen and if you’re still having trouble coming across a Raspberry Pi as they sort out supply issues, something like this might make an excellent substitute at a fraction of the price. If you’re looking to expand even beyond this build, one of the gold standards for ESP32-based automation design is this build from [Marcus] which not only demonstrates how to build a system like this but goes into great detail on the ESPHome environment.

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Moisture Duck Gives You A Green Thumb

Around the Hackaday bunker, any plant other than a cactus has a real chance of expiring due to thirst. Perhaps we should build some of [MakersFunDuck]’s Moisture Duck boards. As you can see in the video below, the simple PCB with an ATtiny13A tells you when it is time to water the plants. The video also covers several exotic methods of determining the watering status, some of which are pretty complex.

The board is simple because the operation of the device is simple. A fixed resistor creates a voltage divider with the soil, and dry soil has higher resistance than moist soil. A pot sets a threshold, and the microcontroller measures the voltages.

Of course, if you can’t remember to water the plants, you probably can’t remember to change batteries either. So the device sleeps most of the time, and only wakes up every eight seconds to conserve battery. It would be nice to alarm on a low battery, and, honestly, we would probably have made the sleep time longer.

The video covers how he minimizes corrosion, but we aren’t sure how well the board will survive in damp soil, but with a little protection, it might last a while. Besides that, you could probably just consider them almost disposable.

If you are really lazy, you can also automate the actual watering. You can even build that into a smart flower pot.

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My Great-Great-Grandad, The Engineer Who Invented A Coffee Pot

In the study of genealogy it’s common to find people who will go to great lengths involving tenuous cross-links to establish royalty or famous figures such as George Washington or William Shakespeare in their family tree. There’s no royal blood and little in the way of fame to be found in my family tree, but I do have someone I find extremely interesting. One of my great-great-grandfathers was a Scottish engineer called James R Napier, and though his Wikipedia entry hasn’t caught up with this contribution to 1840s technology, he was the inventor of the vacuum coffee pot.

James R NapierHe was born in Glasgow in 1821 and was the son of a successful shipbuilder, Robert Napier, into whose business he followed once he’d received his education. He’s probably most well known today for his work in nautical engineering and for inventing Napier’s Diagram, a method for computing magnetic deviance on compass readings, but he was also a prolific engineer and author whose name crops up in fields as diverse as air engines, weights and measures,¬† drying timber, and even the analysis of some dodgy wine. The coffee percolator was something of a side project for him, and for us it’s one of those pieces of family lore that’s been passed down the generations. It seems he was pretty proud of it, though he never took the trouble to patent it and and thus it was left to others to profit from that particular invention.

Vacuum Coffee Pots: Impressive, But Slooow

Just what is a vacuum coffee pot, and what makes it special? The answer lies in the temperature at which it infuses the coffee. We take for granted our fancy coffee machinery here in the 21st century, but a century and a half ago the making of coffee was a much simpler and less exact process. Making coffee by simply boiling grounds in water can burn it, imparting bitter flavours, and thus at the time a machine that could make a better cup was seen as of some importance. Continue reading “My Great-Great-Grandad, The Engineer Who Invented A Coffee Pot”

When Your Smart Light Switches Stop Working, Build Your Own

If you want smart light switches in your house, you can buy from any one of hundreds of manufacturers. [Brian Boyle] had kitted out his home with TP Link devices, but after a few years of use, he found they all suddenly failed within a few months of each other. Decrying the state of things, he set about building his own instead.

[Brian]’s switches use the ESP32 for its handy in-built WiFi hardware. His aim was to produce smart switches that would fit neatly into standard “Decor” style switch boxes. The design uses two PCBs. One is charged with handling the mains power side of things. It carries an SPDT relay for switching AC power, and a DC power supply to run the ESP32 itself. The controller board holds the microcontroller, a Neopixel as a status indicator, and a pair of buttons — one for switching the lights on and off, the other for resetting to default settings. The physical housing is 3D printed, and looks great with the glowing status indicator in the middle of the switch.

[Brian]’s switches are triggerable via MQTT, a web interface, and the physical button onboard the device itself. Having built the devices on his own, he’ll be well-placed to troubleshoot any usability or reliability issues that crop up in the future. That’s a lot more than we can say about most smart devices on the market!