3

FORGE

Live wire of

mains lead

(220V)

YOU’VE GOT MAIL
The full code for this project is available at
hsmag.cc/CZSPYm, so cross-check your code with
that when you’re done editing. To make the code run
as the Raspberry Pi starts up, use the Terminal to edit
the file rc.local. Enter sudo nano /etc/rc.local, and
add the line sudo python /home/pi/IoTea.py & at the
end of the file, but before the exit 0 line. If you saved
your file somewhere else or under a different name,
modify that line to point to your file.
The last code step is to refine the variables. This
will likely get messy – make sure your electronics
are well away from the setup and in a water-resistant
place when you do this! There’s a lot of trial and
error involved. You need the value for the filling to be
conservative, so there’s no risk of the cup overflowing
(but not too conservative or you’ll have a glass half
empty). If you can do this near your screen it saves a lot
of time. Test it by putting the input tube in your water
tank and the output in a mug. Then test the kettle.
You’ll need to fill it to the bottom of the valve, and then
empty the mug of water in. Plug it into the mains, and
time how long it takes to boil. Add a few seconds (we
aren’t bypassing the kettle’s in-built switch so there’s
no need to be exact here – the kettle will turn off when
it’s boiled). The final step is to see how long it takes to
empty the kettle. Again, you can add a few seconds on
here. Change the variable values within the code, save
it, and then shut down the Raspberry Pi.

ALL ABOUT TIMING
Now you just need to wire up the kettle. Unplug it from
the mains, and re-route the live (brown in the UK) wire
to pass through the NO contacts of the Beefcake relay.
Do not undertake this if you don’t know what you’re
doing – if in doubt, consult someone qualified! You’ll
also need to connect your 12 V power supply to the
regulator board if you haven’t already done that.
Now it’s time to test! Make sure the switch on
the kettle is pressed down so that when the relay

activates, the kettle will actually turn on. Place a cup

containing the teabag of your choice underneath the

kettle’s spout, and unplug the Raspberry Pi from your

programming setup.

You’ll need to make sure there’s enough water in the

kettle so that it just reaches the bottom of the valve.

Plug the 12 V power supply in, wait a couple of minutes

for the Pi to boot up, and press the button. You should

get a freshly made cup of tea!

Now the moment of truth – try firing off an email to

the Gmail address you created earlier, and you should

get another piping hot cuppa!

The final part of the puzzle is going to be to add

the I in IoT. It’s all very well being able to send off an

email to make yourself a cuppa, but even that is a bit

too much of a faff when you’re desperate to quench

your thirst after an evening’s hacking. Set up an IFTTT

account using the Gmail address you created earlier

(it’s important to do this with the specific email address

• even if you’ve already got another account). Click
  the ‘create a new applet’ button, and pick ‘Google
  Assistant’ as the IF skill. Set it up with the Google
  account you use every day, and enter values so that
  you can ask it to make a cuppa. Then, for the THAT
  skill, select ‘Email’. Enter whatever subject and
  content you like, as that’s invisible to the code. Save
  the applet.
  The final step is to package everything up into a
  case. We used an old chocolate tin, spray-painted
  black. This serves two purposes: keeping the
  electronics dry, and lifting the kettle above the cup so
  it pours out properly into the mug. Now you can make
  a cup of tea by simply talking to your phone! Welcome
  to the future – two lumps for us, thanks.

Whilst this

project uses a

Raspberry Pi

as the brain,

there are lots of

other boards you

can use for IoT

projects like this.

An Arduino would

work well and

ESP8266 boards

would be a good

choice if you

want to connect it

to a network.

BRAINS

OTHER

Raspberry Pi Zero W

GPIO 2

+V COM +V COM +V

NO NO COM

Pump Valve

NO

gnd gnd

gnd

Control Control

Control

GPIO 3

Ground

+

12V

Power

Supply

• Pump Relay Valve Relay kettle relay‘Beefcake’

5V

regulator

To Kettle

Button

GPIO 5

+5VGPIO 26

Above

The system is a

complicated one,

but well within

the realm of the

average maker

Above

And there you have it: an IoT connected, Raspberry Pi Powered

tea machine, complete with steampunk spout!