Sniffed Transformer Puts Wired Doorbell Online

August 6, 2019 by Tom Nardi 30 Comments

There’s certainly no shortage of “smart” gadgets out there that will provide you with a notification, or even a live audiovisual stream, whenever somebody is at your door. But as we’ve seen countless times before, not everyone is thrilled with the terms that most of these products operate under. Getting a notification on your phone when the pizza guy shows up shouldn’t require an email address, credit card number, or DNA sample.

For [Nick Touran], half the work was already done. There was already a traditional wired doorbell in his home, he just had to come up with a minimally invasive way to link it with Home Assistant. He reasoned that he could tap into the low-voltage side of the doorbell transformer and watch for the telltale fluctuations that would indicate the bell was doing its thing. The ESP8266 has an ADC to measure voltage and WiFi to connect to Home Assistant, so it seemed like the perfect bridge between old and new.

Of course, as with any worthwhile project, it ended up being a bit more complicated. Wired doorbells generally operate on 16-24 VAC, and [Nick] knew if he tried to put his Wemos D1 across the line he’d release the critical Magic Smoke. What he needed was a voltage divider circuit that would take low-voltage AC and drop it to an even lower DC voltage that the microcontroller could cope with.

The simple circuit [Nick] comes up with cuts the voltage way down and removes the negative component completely. So what was originally 18.75 VAC turned into a series of 60 Hz blips at 2.4 VDC; perfect for feeding into a microcontroller ADC. With a baseline to work from, he could then write some code that would watch for variations in this signal to determine when the bell was ringing.

Or at least, that was the idea. While the setup worked well enough on the bench, its performance in the real-world left something to be desired. If his house guest had a heavy hand, it worked great. But a quick tap of the doorbell button would tend to go undetected. After investigating the issue, [Nick] found that he needed to use some software trickery to ensure the ESP8266 was able to keep up with the speedy signal. Once he was able to reliably detect short and long button presses, the rest was just a simple matter of sending an MQTT message to his automation system.

Compared to the hoops we’ve seen other hackers have to jump through to smarten up their doorbells, we think [Nick] got off fairly easy. This project is also an excellent example of how learning about circuit design and passive components can still come in handy in the Arduino Era.

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Building A Safe ESP32 Home Energy Monitor

July 27, 2019 by Tom Nardi 45 Comments

The first step to reducing the energy consumption of your home is figuring out how much you actually use in the first place. After all, you need a baseline to compare against when you start making changes. But fiddling around with high voltage is something a lot of hackers will go out of their way to avoid. Luckily, as [Xavier Decuyper] explains, you can build a very robust DIY energy monitoring system without having to modify your AC wiring.

In the video after the break, [Xavier] goes over the theory of how it all works, but the short version is that you just need to use a Current Transformer (CT) sensor. These little devices clamp over an AC wire and detect how much current is passing through it via induction. In his case, he used a YHDC SCT-013-030 sensor that can measure up to 30 amps and costs about $12 USD. It outputs a voltage between 0 and 1 volts, which makes it extremely easy to read using the ADC of your favorite microcontroller.

Once you’ve got the CT sensor connected to your microcontroller, the rest really just depends on how far you want to take the software side of things. You could just log the current consumption to a plain text file if that’s your style, but [Xavier] wanted to challenge himself to develop a energy monitoring system that rivaled commercial offerings so he took the data and ran with it.

A good chunk of his write-up explains how the used Amazon Web Services (AWS) to process and ultimately display all the data he collects with his ESP32 energy monitor. Every 30 seconds, the hardware reports the current consumption to AWS through MQTT. The readings are stored in a database, and [Xavier] uses GraphQL and Dygraphs to generate visualizations. He even used Ionic to develop a cross-platform mobile application so he can fawn over his professional looking charts and graphs on the go.

We’ve already seen how carefully monitoring energy consumption can uncover some surprising trends, so if you want to go green and don’t have an optically coupled electricity meter, the CT sensor method might be just what you need.

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Building A Smarter Smoke Alarm With The ESP8266

July 26, 2019 by Tom Nardi 9 Comments

The modern hacker wields a number of tools that operate on the principle of heating things up to extremely high temperatures, so a smoke alarm is really a must-have piece of equipment. But in an era where it seems everything is getting smarter, some might wonder if even our safety gear could benefit from joining the Internet of Things. Interested in taking a crack at improving the classic smoke alarm, [Vivek Gupta] grabbed a NodeMCU and started writing some code.

Now before you jump down to the comments and start smashing that keyboard, let’s make our position on this abundantly clear. Do not try to build your own smoke alarm. Seriously. It takes a special kind of fool to trust their home and potentially their life to a $5 development board and some Arduino source code they copied and pasted from the Internet. That said, as a purely academic exercise it’s certainly worth examining how modern Internet-enabled microcontrollers can be used to add useful features to even the most mundane of household devices.

In this case, [Vivek] is experimenting with the idea of a smoke alarm that can be silenced through your home automation system in the event of a false alarm. He’s using Google Assistant and IFTTT, but the code could be adapted to whatever method you’re using internally to get all your gadgets on the same virtual page. On the hardware side of things, the test system is simply a NodeMCU connected to a buzzer and a MQ2 gas sensor.

So how does it work? If the detector goes off while [Vivek] is cooking, he can tell Google Assistant that he’s cooking and it’s a false alarm. That silences the buzzer, but not before the system responds with a message questioning his skills in the kitchen. It’s a simple quality of life improvement and it’s certainly not hard to imagine how the idea could be expanded upon to notify you of a possible situation even when you’re out of the home.

We’ve seen how a series of small problems can cascade into a life-threatening situation. If you’re going to perform similar experiments, make sure you’ve got a “dumb” smoke alarm as a backup.

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Homekit Compatible Sonoff Firmware Without A Bridge

July 14, 2019 by Tom Nardi 38 Comments

Generally speaking, home automation isn’t as cheap or as easy as most people would like. There are too many incompatible protocols, and more often than not, getting everything talking requires you to begrudgingly sign up for some “cloud” service that you didn’t ask for. If you’re an Apple aficionado, there can be even more hoops to jump through; getting your unsupported smart home devices working with that Cupertino designed ecosystem often involves running your own HomeKit bridge.

To try and simplify things, [Michele Gruppioni] has developed a firmware for the ubiquitous Sonoff WIFI Smart Switch that allows it to speak native HomeKit. No more using a Raspberry Pi to act as a mediator between your fancy Apple hardware and that stack of $4 Sonoff’s from AliExpress, they can now talk to each other directly. In the video after the break you can see that the iPad identifies the switch as unofficial device, but since it’s compliant with the HomeKit API, that doesn’t prevent them from talking to each other.

Not only will this MIT licensed firmware get your Sonoff Basic, Sonoff Slampher, or Sonoff S26 talking with your Apple gadgets, but it also provides a web interface and REST API so it retains compatibility with whatever else you might be running in your home automation setup. So while the more pedestrian users of your system might be turning the porch light on with their iPhones, you can still fire it up with a Bash script as nature intended.

Of course, if you don’t mind adding a Raspberry Pi bridge to the growing collection of devices on your network, we’ve got plenty of other HomeKit-enabled projects for you to take a look at.

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Reverse Engineering WyzeSense Hardware

June 11, 2019 by Lewin Day 6 Comments

Wyze are a company that produces a variety of home automation products. Their Wyze Sense package is a system of contact and PIR home security sensors, that piggy backs off their Wyze Cam product. In the interests of being able to use this hardware outside the prescribed corporate ecosystem, [Xuan Xing] got down to hacking.

The project starts by tearing down the Wyze Cam, and getting serial console access. This was made easier by an existing Github project, which develops custom firmwares for smart cameras. With that in place he was able to see what was going on under the hood, and read the camera’s system logs.

By poring over these logs, and examining the disassembled Wyze Sense dongle, he’s well on the way to discovering how the sensors communicate with the Wyze Cam. The end goal is to enable the Wyze security sensors to be used with the Raspberry Pi platform, and to share the code on Github for other makers to experiment with.

Home automation platforms come and go quicker than the seasons change. This makes the hardware a popular target for hackers trying to get things running independently of any one company’s servers.

HestiaPi: A Stylish Open Hardware Thermostat

June 11, 2019 by Tom Nardi 20 Comments

A common complaint about open hardware and software is that the aesthetic aspects of the projects often leave something to be desired. This isn’t wholly surprising, as the type of hackers who are building these things tend to be more concerned with how well they work than what they look like. But there’s certainly nothing wrong with putting a little polish on a well designed system, especially if you want “normal” people to get excited about it.

For a perfect example, look no further than the HestiaPi Touch. This entry into the 2019 Hackaday Prize promises to deliver all the home automation advantages of something like Google’s Nest “smart” thermostat without running the risk of your data being sold to the highest bidder. But even if we take our tinfoil hat out of the equation, it’s a very slick piece of hardware from a functional and visual standpoint.

As you probably guessed from the name, the thermostat is powered by the Raspberry Pi Zero, which is connected to a custom PCB that includes a couple of relays and a connector for a BME280 environmental sensor. The clever design of the 3D printed case means that the 3.5 inch touch screen LCD on the front can connect directly to the Pi’s GPIO header when everything is buttoned up.

Of course, the hardware is only half the equation. To get the HestiaPi Touch talking to all the other smart gadgets in your life, it leverages the wildly popular OpenHAB platform. As demonstrated in the video after the break, this allows you to use the HestiaPi and its mobile companion application to not only control your home’s heating and air conditioning systems, but pretty much anything else you can think of.

The HestiaPi Touch has already blown past its funding goal on Crowd Supply, and the team is hard at work refining the hardware and software elements of the product; including looking at ways to utilize the unique honeycomb shape of the 3D printed enclosure to link it to other add-on modules.

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Smarten Up Your Air Conditioning With The ESP8266

June 11, 2019 by Tom Nardi 14 Comments

If you’re looking for “smart” home appliances, there’s no shortage of options on the market. Even relatively low-end gadgets are jumping on the Internet of Things bandwagon these days (for better or for worse). But what if you’re not looking to purchase a brand new major appliance right now? In that case, you might be interested in seeing how [Giulio Pons] added some high-tech features to his existing air conditioner on the cheap.

Since his AC unit had an infrared remote control, the first thing [Giulio] needed to do was come up with a way to emulate it. An easy enough project using the ESP8266 and an IR LED, especially when he found that somebody had already written a IR communications library for his particular brand of AC. From there, he could start tacking on sensors and functionality.

With the addition of a DHT11 sensor, [Giulio] can have the AC turn on and off based on the current room temperature. It also gives him an easy way to verify the AC is actually on and operating. By checking to see if the room starts cooling off after sending the IR command to start the AC, his software can determine whether it should try resending the code, or maybe send a notification to alert him that something doesn’t seem right. Of course, it wouldn’t be a proper ESP8266 project without some Internet connectivity, so he’s also created a smartphone application that lets him control the system while away from home.

Now admittedly nothing in this project is exactly new, we’ve seen plenty of hackers switch on their AC with the ESP8266 at this point. But what we particularly liked was how well thought out and documented the whole process was. The rationale behind each decision is explained, and he even documented things like his network topology to help illustrate how the whole system comes together. Even if the techniques are well known by many of us, this is the kind of project documentation that makes it accessible to newcomers. Our hats off to [Giulio] for going the extra mile.

In the past we’ve seen a similar project that allowed you to control your AC from Slack, and our very own [Maya Posch] took us on a whirlwind tour of the very impressive ESP8266-powered environmental monitoring system she helped develop.