Control Sonoff Switches with Google Home (Part 1)

Getting into home automation doesn’t have to cost a fortune, if you’re willing to do a little bit of work!

Building your own IoT ecosystem will keep you immune from planned obsolescence, disappearing back-end services,  all while minimize vulnerabilities.  In this series, we’re going to show you how to build some devices that will let you say “Hey Google, turn off the lights!”  (Yes, just like Captain Picard from Star Trek, saying “Tea. Earl Grey. Hot.” and having your automated home make it for you, is not an impossibility. )

There are a few components needed to make this work.  The relays and the voice device, mainly, (Google Home, Siri, Alexa, Etc.) I’m starting with Google Home, since that fills an immediate need I have.

You’ll need an Internet-connected server of some sort, with a port open to the world.  A Raspberry Pi is powerful enough for this task.  It can be a remote server, if you like, even an obscure corner of an existing web site—we’ll just need to install a few PHP scripts to serve as webhooks for IFTTT.  If you’re using a Raspberry Pi, you can also host your own MQTT server.  If not, you can use a public one to get started. More on that later. First, let me introduce you to a remarkable bit of kit, the Sonoff!

The Sonoff is an Internet of Things component that you really need to be aware of:

Sold as a “WiFi Smart Switch,” its a nicely-packaged Internet-controlled relay.

Here’s a look inside:

The green terminal blocks at each end are such that you could chop a lamp cord, strip off 1/8″ of insulation, screw them in to the terminal blocks and have an Internet-controlled lamp. The yellow thing is a transformer, which, along with the capacitors and the varistor, form a 3.3v power supply that powers the device. (No USB cables and adapters needed!)

The relay is the black block with a white label, just below “worth” on the Way Cool Beans coaster.  (Way Cool Beans is the coffee shop where we dream up all of this stuff.  It’s a great place to get coffee, they do all their own roasting, by hand, on site and run their web server from a Raspberry Pi inside a glass head. They also host all of our classes. How cool is that?)

Here’s the back of the board:

There’s a couple of things that stand out here.  See those heavy solder traces?  That’s where the housecurrent (mains) power crosses the board.  The upper trace is the neutral and the lower one is the live current.  The two are nicely separated, even to the extent that there is a gap cut into the board, to keep it from shorting out.

It’s important to keep in mind that this board is designed to handle AC voltages that can kill you—never power it it up when it’s outside of its protective housing! (We’ll be programming it later, which requires you to feed it DC 3v with the case off, but that’s safe enough.) Use common sense and have a responsible adult handy, if you don’t happen to be one yet.

In the bottom left, you can see the “squiggle” of the onboard wifi antenna.

So why is this thing so special?  It’s got a built-in ESP8266! That means we can easily reprogram this thing to do all sorts of cool stuff, using open-source code that we can easily inspect and modify!  Here’s a package (Programmed with the Arduino IDE) that I absolutely adore for turning the Sonoff into a really great, easily-configured relay that we can control via MQTT!

There are a bunch of different ways to put your code onto an ESP8266, but by far, the easiest is to use the Arduino’s IDE, or “Integrated Development Environment.” Here’s a tutorial that explains how to install and configure your Arduino Environment. (Scroll down to “Installing and Configuring.”)

You’ll need to get yourself a USB to TTL Serial Adapter if you don’t have one already.  Be sure it’s set to 3.3v when programming ESP8266 devices!

Jonathan at SuperHouseTV on YouTube has an episode where he shows how to flash your own firmware onto the Sonoff.  (Jump to 17:35 to get right to that section, or watch the whole thing, if you have time.) Keep in mind that we’ll be flashing a different package onto the Sonoff.

OK – That’s going to do it for the first part of this tutorial.

A Morse Code Application for MQTT

1878 Bunnell Telegraph Set

[Github Repo of the Code – see for this script.]

Telegraphy and Morse Code were the first instantaneous long distance form of communication.  Invented in 1844, for the first time, you could communicate in real time with someone you could neither see nor hear.

Telegraphy was huge.  It was the Internet of its day.  But the truth is, it was actually pretty simple:

A telegraph is something you can build in an afternoon.  The basic principle is electro-magnetism.  If you wrap wire around an iron nail, it becomes a magnet when you run electricity through it.

A telegraph sounder like the one below works by becoming magnetic electrically, which causes a spring-loaded tapper to click against it audibly.

1878 Bunnell Telegraph Set
1878 Bunnell Telegraph Set

In the age of Internet communications, this may all seem obsolete, but there are thousands of people around the world who still communicate via Morse code, primarily over radio.  These amateur radio operators, or HAMs, as they are called, don’t need Internet to communicate around the world, so they become of vital importance in times of natural disaster, or any time other forms of communication don’t work, both with voice radio and Morse Code.

In the photo is a pair of telegraph stations manufactured by J. H. Bunnell & Co., in 1878.

Now, many people would put something like that in a nice display case and never play with it, but where’s the fun in that?

Raspberry Pi to the rescue!

The Raspberry Pi has a bank of pins known as General Purpose Input/Output (GPIO) pins that we can use to send a bit of electricity to light up an LED.  It’s not much, only around 3 volts, but we thought it might be just enough to make the sounder click.  With careful adjustment of the sounder’s springs and set screws, we were able to get a good click.

With that first test out of the way, it’s time to write some code!

I started, as all good programmers do, by Googling for some code to steal borrow to save me some of the heavy lifting.  I came across a tutorial from Cambridge University in England.  Linked from that was a Python script that would get us started.

What this script does is ask you to type something and hit enter, then it blinks it out as code on an LED.  That’s close, but to make this interesting, let’s get it hooked up to the Internet, so we can receive Morse messages from anywhere in the world!

MQTT is a server protocol that’s a lot of fun to play with.  It’s a simple way to send messages from one device to any number of other devices.  You can also do a kind of chat with it, since it’s so fast and simple.

Let’s go get the code!  On your Pi, open the terminal.

Pi Terminal
Type the following commands:


This command takes you to your home directory. It’s a good place to work. Next, we’re going to go grab the code from Github:

git clone

You should see output that looks like this:

cd electrobrain

to change to the project’s directory. Next, type

idle ~/electrobrain/

to open the program in the Idle Python Editor:


Once you have the project open in Idle, try running it by hitting the F5 key on your keyboard, or by clicking “Run > Run Module” with your mouse.

You may get an error.  That’s OK, it’s probably just a missing library.  Probably the MQTT library we use.  To install Python libraries, we use a program called “pip”.  First, let’s make sure we have pip.  We ask Linux if it knows pip:

which pip

It should come back with:


If you just get a blank line when you hit enter, it means it isn’t installed.  Let’s install it!

sudo apt-get update
sudo apt-get install -y python-pip

OK, pip should be installed now.  We should only need to do that once.

OK, now type:

sudo pip install paho-mqtt

Now try running the script again from Idle. If everything is working, it will say:

Connected to:
with result code: 0

If you get that, pat yourself on the back.  (Seriously.  You’ve actually accomplished quite a bit.)


Now it’s time to hook something up to the Pi’s GPIO.  In the program, I’ve specified pin 25 as the one that will turn on.  Below is a diagram of the pins on a Raspberry Pi 3.  The ones on the right are on the outside edge of the board.


Get yourself your little breadboard, a resistor (220 Ohm) and an LED.  Hook it up like this diagram:


Now go back to Idle and run the program again.  It should be listening, ready to blink out your code, but it’s not likely that anyone is sending a message to that channel.  Let’s go send some data!

Open a new terminal and type:

sudo apt-get update
sudo apt-get install -y mosquitto-clients

When that’s finished, we’re ready to send!

mosquitto_pub -h "" -t "test/abcd" -m "What Hath God Wrought!"

Why “What Hath God Wrought!”?  Well, as it turns out, that was the first message sent by inventor Samuel F.B. Morse on May 24, 1844.

Did it work? (If it didn’t, feel free to leave a comment below.)

If so, try this:

mosquitto_pub -h "" -t "test/abcd" -l

Then type one message per line and hit enter.  Each line should be sent to your LED as Morse Code!