brew perfect beer with help from the raspberry pi

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• Brewing
• Cooling
• Fermenting
• Priming
• Bottling
• Ageing
• Drinking
The following tutorial
mixes liquid, electricity
and DIY modifications,
all of which can create
a lethal cocktail of
danger. Don’t make any
modifications yourself
unless you’re certain
they’re safe, and get a
qualified electrician to
check any modifications
you do make.
We love beer, we love the Raspberry Pi and we love the Arduino
– so we’re bringing them together for one awesome project.
eer is lovely. But when you’re making it at
home, the biggest challenge (after discovering
a way to boil vast quantities of water) is always
finding somewhere to leave your brew to ferment. It’s
this stage of beer-making magic that turns what’s
known as wort into beer, creating alcohol and oodles
of flavour. And for this stage to work well, you ideally
need to be able to manage the temperature of the
environment your beer is sitting in. In the UK, many
amateur brewers resort to using an ‘airing cupboard’,
normally situated next to the hot water tank and used
for drying clothes. This isn’t a bad place, because it’s
warmish – many beer kits like to ferment at around
20 degree centigrade – and the temperature doesn’t
fluctuate massively. But it still fluctuates, and it may
even prove too warm. Many yeasts, especially for ale,
prefer things a little cooler (18–20 degrees, ideally, but
this depends on the beer). And lifting 25 litres of wort
into a first-floor cupboard could break your back, and
you’ve got a hygiene nightmare if it falls over, or falls
through the flimsy shelf its sitting on.
BrewPi is the answer to this conundrum. It’s a
brilliant project that brings together a love of Linux, a
little hardware hacking and plenty of beer into one
fermenting barrel of hoppy goodness. It’s essentially a
device that controls the environment surrounding the
fermenting bucket of beer, enabling you to make
perfect beer every time, regardless of climate and
house heating cycles. Many people use an old fridge
or freezer as the surrounding container and connect
the BrewPi to a cooling and heating mechanism to
enable its clever algorithms to create the perfect
environment for your beer. The BrewPi itself is a
mixture of hardware, software and initiative. Not only
This shows the rear of the LCD connecting to the Arduino
and the shield, with the OneWire connector above.
The various bits of the BrewPi give little indication that
they can be put together to create something awesome.
has its creator, Elco Jacobs, built an incredibly
effective system for fermenting beer, he’s created an
extremely helpful community of BrewPi enthusiasts,
an online shop and an assembly system for easy
access to all of the bits and pieces you’ll need.
What you’ll need
While you will need a fair bit of kit, it needn’t cost very
much. The fridge or freezer is the biggest
consideration, as well as somewhere to put it. We
asked the internet, and Mark Einon in Wales very
generously obliged with a freezer he was going to give
to the local freecycle initiative (thanks Mark!) Almost
any fridge or freezer will do, as long as it’s working,
and you should be able to find someone willing to let
an old model go for very little. You need enough space
within the freezer to stand your fermenting bin, and as
our freezer’s shelves were made from coolant pipes,
we had to bend these back before there was enough
room. Fortunately, the pipes were easily pushed back.
We then slotted in an old wooden shelf to stand the
fermenting bucket on, as they can be very heavy when
full of 25 litres of brewing beer.
If the fridge or freezer has an inside light, this can be
coerced into another essential task – heating up the
inside environment. If not, you’ll need some other kind
of heating mechanism. Some people use a reptile mat
wrapped around the fermenting bin, but we plumped
for a 60W waterproof greenhouse heating bar, which
cost us £15 new on eBay, and slotted nicely into the
bottom of the freezer with plenty of room. You will
also need both a Raspberry Pi, complete with a > 2GB
SD card, and either an Arduino Duo or an Arduino
Leonardo microcontroller. If you’re anything like us,
you’ve got an old Duo tucked away in a drawer
somewhere and a Raspberry Pi going spare. And
despite the name of the project, there’s no specific
reason for requiring a Raspberry Pi – any Linux device
with a USB port capable of running the Apache web
server and some Python scripts should be up to the
job. You might want to try a NAS, for example, if you’re
running one already. But the Pi is well suited to being
tucked away in the garage, and it’s relatively cheap, so
it’s still a great option. Most of the hard work is done
by the Arduino, as this interfaces with the various
sensors and relays and runs the complex controlling
algorithms that adjust the temperatures within your
freezer. Your brew will even keep brewing if the Pi
crashes, which is handy if there’s a power failure and
your Pi develops a read/write error. The Pi is really just
logging and serving up the data for the web portal.
Unless you’re an expert who’s happy building
circuits, you’ll also need the BrewPi kit (
This includes everything you need to turn your
Arduino into a sensor-wielding beer factory. It includes
the shield, a PCB that slots onto the two compatible
Arduino form factors, along with the LCD, the sensors,
the actuators (more details later if none of this makes
sense) and the other fiddly bits that may otherwise
take an afternoon to source. It’s even possible to buy
the whole thing pre-constructed, but we think that’s
missing half the fun, especially when the build itself
isn’t that difficult.
We’d also highly recommend buying the case kits.
These lasered bits of plastic encase both your
Raspberry Pi and your Arduino to create a sleek,
professional solution that looks great sitting atop your
freezer. They also stop bits getting bashed about or
falling off. Expect to pay around £70 for the shield and
case kits together. You’ll also need a miscellany of
common tools to put the whole thing together; a
soldering iron and solder, maybe a solder sucker,
some tweezers, a range of differently sized
screwdrivers and a steady hand.
Did we just say soldering iron? Yes! You’ll need to
solder the various components on to the Arduino
shield. But it’s straightforward, and this should make
an ideal first project if you’ve not done any soldering
before. All the components are large and there’s no
fiddly soldering required. Try watching a couple of
YouTube soldering videos to familiarise yourself with
The Raspberry Pi can also fit on top of the BrewPi case,
in a separate box or au naturel. Cases are good.
the process first, and then experiment a little with an
old circuit board and some wire. You’ll then be set for
the main event.
The shield is the bit that attaches to the Arduino,
and it’s probably the most complex part of the whole
assembly, so let’s get this out of the way first. The
main instructions can be found at
brewpi-soldering-guide, but we’re going to cover the
broad detail of the process, along with any particular
notes we make along the way. The official instructions
are made up of photos, and while they’re great if you
know what you’re doing, we want to make the project
as accessible as possible by making fewer
assumptions about the builder than the official site.
The BrewPi isn’t an easier
way of making beer. It’s
an easier way to make it
Forging the shield
First, lay out all the components on a table top,
grouping them together so you can check they’re all
there. This also makes it easier to install. Now start by
being brave – you’ve got to snap the shield apart into
four separate boards. It’s a little like breaking bonfire
toffee. The large board that breaks off (labelled with connects directly to the Arduino.
Then there’s a long strip embedding seven columns of
three holes, a medium-sized rectangle of a board with
a surface mounted integrated circuit, and a tiny
rectangle that will host the rotary encoder.
Break off the broken tabs remaining on the boards
with a pair of pliers or a small pair of cable cutters so
that the edges are as smooth as possible. Some of
the pin arrays – the ones with the two collars of black
plastic – are designed to fit on to your Arduino board
so that it can connect to the holes on the shield. There
are five of them, and you should find there’s one for
every header on the Arduino. These need to be
connected to the Arduino first, before being soldered
into the shield – this locks their orientation and
connection. The longer pin goes into the Arduino,
while the shorter piece goes into the shield. As we
were using an ancient Arduino Uno, there were fewer
power headers on the circuit board that pins allocated,
Red or blue LEDs on the
shield indicate whether the
BrewPi is currently heating
or cooling your brew.
Soldering tips; heat up
the destination first,
dab the solder onto the
joint, make sure it flows
into the joint naturally
and try not to bridge any
connections. If you do,
heat and remove using a
solder sucker.
but the eight-pin array still fitted over the power pins
and the 10-pin header still fitted across the IO pins
without getting in the way of everything coming
together. Don’t forget there’s also smaller six-pin
rectangular connector. Fortunately, the shield only fits
one way. Start your soldering at the corners to make
sure all the pins stay aligned.
Now solder the single green connector onto the
ACT1–ACT 4 shield holes, with the component
attached to the side with the website URL. Connect a
three-pin green connector to one side, and one of the
two-pin connectors to the other (they all offer ports at
right angles to the board, and have the same
connector form factor as the eight-pin one you’ve just
connected). Ours wobbled slightly while fitting them,
so it’s best to solder one of the middle pins first and
wiggle the connector into alignment, before soldering
any remaining pins. Flip the shield over and solder one
of the 10-pin block connectors to the header labelled
“To the LCD backpack”, and make sure you’ve got the
gap in the right place (facing the edge).
That’s all that needs to be done to the main board!
Congratulations. Now might be a good time for a cup
of tea before moving on to the LCD backpack itself.
Glowing electronic display
The LCD board is the one with the small integrated
circuit already on it. The circular speaker fits into the
middle with the upwards side on the same side as the
chip, and after soldering, you need to cut the
protruding pins from the other side. Another 10-pin
header comes next, with the gap facing the integrated
circuit. Flip this small board over (to the side without
any components), and fit the 16-pin header into the
holes. Solder from the other side.
The tiny board for the rotary encoder is up next. The
official instructions mention that the biggest two pins
on the encoder need to be squeezed slightly to fit into
the holes. We didn’t need to do this, but we did need to
use a fair amount of strength to get the encoder into
position. Make sure the side with the handle is the one
with the circle on the board, and solder the joints from
the other side. A washer, a nut and then the handle
can be slipped over the encoder when you’ve finished.
Next is what’s known as the OneWire distribution
board (the only board remaining). Sometimes it’s
written as ‘1-Wire’, and it’s a standard protocol for
communicating with devices from Dallas
Semiconductor (such as the temperature sensors we
need for our BrewPi), using a single connector, hence
its name. This needs seven of the three-pin green
connectors – two shaped at right angles for the edge
connectors, and the other five directly pointing up (you
can see this illustrated on the board itself now you
know what to look for, and that’s the side they need to
be connected to). Official instructions suggest starting
with the two outer connectors, as these are oriented
outwards lengthways. The other five all face upwards
with their pins on the left when you’re looking at the
text on the board. The green ‘AT-AT’ connectors (for
that is what they look like, not an official designation)
then plug into these and the two end connectors.
Now it’s the turn of the rainbow-coloured ribbon
cable, which we need to turn into something a little
more civilised to enable it to connect to the ports
we’ve been soldering. If you’ve ever made your own
IDE cable for an ancient PC, this is very similar. The
black plastic connectors that attach themselves to the
ribbon cable have teeth that penetrate the insulation
on the outside of the wire to make a connection
without soldering anything. Just make sure the
triangles on the connector align with the black wire in
the flat cable. Push the cable through until it just
protrudes from the other side, and taking the advice of
the official instructions again, place the smaller edge
on a table and use something flat to put considerable
pressure onto the connector. It should just about
come together, and in so doing, connect the pins to
the cable. When this seems secure, fold the long end
of the cable up and over the back of the connector
before sliding the remaining black connector to hold
the cable together. This needs to be done on both
sides of the ribbon cable, and both connectors need to
point the same way so that the cable won’t twist. That
last bit can be a little mind bending as you try to work
We had to bend one of the shelves in our freezer to make
enough room for the fermenting bin.
The LCD, which fits
into the hole in one
of the case panels.
The flat packed
Raspberry Pi and
Arduino shield cases.
Shield parts are
mostly soldered
onto the shield,
but our kits had a
few bits left over.
out which way to put the connector on so that the
black cables stay in the same place and the connector
is pointing in the same direction after you’ve twisted
the cable back over the connector. You can now
connect both of the boards with the correctly sized
connector together with the cable, and we felt slightly
more optimistic after testing the continuity of the
connections to make sure we’d pushed through the
connectors to the ribbon cable with enough pressure.
For the other ribbon cable, pull off the ends where
they’ve been cut and wiggle this into the underside of
the rotary controller board. Pin 4 should always be red.
Then solder the pins to the board, The other end of
this cable goes to the LCD board, parallel to the
rainbow ribbon cable, and connected to the same
side. Make sure pin 4 lines up and solder this as well.
The next stage is the LCD, and you first need to
break off 16 pins for the LCD itself. The official guide
has a great tip, where you connect the whole header
to the female header on the other board and use this
as a guide for snapping the 40-pin header at the right
place with your hands. This didn’t quite work for us, as
we broke the header one pin short, but it was easy
To make the sensors inside the fridge easily removeable,
use a connector like this within a container.
Temperature sensors are
used to measure the beer
temperature, the freezer
temperature and the
outside temperature.
The shield itself.
enough to solder the lone pin alongside the others.
Solder these pins on the top surface (the same side as
the LCD itself), and you can now attach the LCD to the
female header.
The final stage of shield forging is to take the
sensors and strip the insulation off the end of the
wires – a couple of millimeters will do. Each cable has
three ‘cores’, and each core needs to be screwed into
a three headed ‘AT-AT’ green connector, so that when
these plug into the OneWire board, red is at the top
(marked 5V – this is important), and yellow at the
bottom. The official instructions note that the colour
order of the yellow and green wires has changed, so
it’s worth making doubly sure if you’re reading this in
the distant future, as the sensors might not be able to
take 5V going in the wrong cable. To make the ends of
the wires easier to insert into the tiny screw holes, and
to make them more resilient, it’s worth dabbing them
in a little molten solder.
Porter, Stout, IPA – and the case
You now have a choice. You can either keep the
OneWire connector close to the rest of your BrewPi
hardware, or place it closer to where the sensors are
going to be. This might be useful if you wanted to
position the OneWire board within the fridge, for
example, but we decided to go with the official
instructions and wire up a short three-core cable
(maybe 20cm), with AT-AT connectors at either end, to
connect the OneWire board to the BrewPi. We used an
old power cable with earth for easy access to three
cores with insulation attached. This cable eventually
loops outside the case from the main board to the
OneWire connector.
The cases are all made from various bits of lasered
plastic, and it’s never clear exactly what goes where.
It’s like a BrewPi 3D jigsaw puzzle. The Raspberry Pi
case is a good place to start, as this is emblazoned
You can check your sensor
devices are working by
enabling the ‘Read values’
option before refreshing
the device list.
with the Raspberry Pi logo flanked by some hops, and
it’s also obvious which way the pieces should go when
you attempt to fit your Pi into the case. The feet of all
the cases are half-circles, which is another good way
of orienting yourself with the 13 or more pieces used
to construct each of the cases.
As we we’re using an early Pi, lacking holes on the
PCB, there’s no way of mounting the board inside the
case. The official instructions show a couple of
spacers and screws mounting the Pi to the lower case
panel. Our case design didn’t have a hole even if we
did want to connect the Pi. But thanks to the various
prominent ports and connectors on the Pi, it was held
firmly in place regardless. One side has the video and
audio connectors, the opposite just an HDMI
connector. Lengthways, theres a micro USB at one
end and USB and Ethernet at the other. It’s also a good
idea to push out any of the small bits of plastic that
are used to create airflow through the case, as the Pi
can be prone to overheating, but we couldn’t remove
some of these pieces as they weren’t separated
enough from the borders of the plastic. This may have
been why two extra end pieces, with all the bits
removed, were hidden away in one of the part bags.
It all goes together easily enough when you’ve
worked out up and down and where each side fits. Be
careful with the side containing the HDMI connector,
as it’s not immediately obvious when it aligns and you
may not notice it’s reversed until the end. When you’ve
got everything held together, you’ve got to now use
the long screws, two at each long end, to go through a
washer, then into the case, and then through a nut you
hold in the small vertical gap before tightening the
whole thing up. It’s fiddly and frustrating, so we’d
suggest focusing on the beer.
Construction time again
This leaves you with significantly fewer bits to worry
about for the other case, which is going to contain our
BrewPi shield. Now, for some reason, our case is a
hybrid of an earlier revision with a few differences
between both the earlier version and the 2.0 cases, so
there’s no point telling you how to put the case
together. In fact, the 3.0 case was announced in
January, and is smaller again. We were able to make it
up as we went along because it’s much easier than
building the shield, and mostly common sense. There
Before we move on to software, you need to give
some consideration to how you’re going to power
both the Raspberry Pi and the Arduino. In theory,
you could power the Arduino from the Raspberry
Pi’s USB, using only a single hub or adaptor. We
tried this with as many milliamps as we could
muster, but the LCD on the Arduino still dimmed
when we did anything. Rather than take any risks
with our beer, we decided to power both separately.
As we all know, the Raspberry Pi is very susceptible
to irregularities in power, so it’s best not to take any
risks – use a high amperage USB hub or adaptor for
the PI, and an appropriate adaptor for the Arduino.
It’s now time to test whether your soldering
skills have been good enough, and to stretch a few
of those Linux skills too! The first step is to get
a working Raspberry Pi configuration, complete
with your chosen method of network connection.
This has been documented many times, so we
won’t go into the details – plus, downloading and
installing NOOBS onto your Raspberry Pi makes
the whole process easier than ever. Just make
sure the Raspbian installation and the firmware is
up to date, because there are some known issues
with Raspberry Pi stability, especially with older
versions. And stability is key when you’re asking a
Raspberry Pi to control temperatures for a week or
two.To update Raspbian, type:
sudo apt-get update
sudo apt-get upgrade
To update the firmware, type:
sudo apt-get install rpi-update
sudo rpi-update
We now need to grab the latest installation tools.
To do that, just enter the following and leave all the
answers at their default values:
git clone
git ~/brewpi-tools
sudo ~/brewpi-tools/
After this has completed, reboot your Pi. You
will now be able to point a web browser on your
LAN to the IP address of your BrewPi. Don’t (yet)
get distracted by the blinking lights, as they’re not
doing anything meaningful. Instead, you need to
upload the BrewPi firmware to the Arduino before
anything can happen. First download the firmware
file itself (here’s the link:
brewpi-avr/stable), and make sure you get the
correct file. The file depends on your Arduino type
and revision – ours is an Arduino Uno Rev A, for
instance. To upload this to your BrewPi, click on
the ‘Maintenance Panel’ button on the right of the
web interface, then click on ‘Reprogram Arduino’.
Select your Arduino from the drop-down menu, then
select the downloaded hex file. Make sure ‘No’ is
answered for both the ‘Restore Old Settings After
Programming’ and ‘Restore Installed Devices After
Programming’ options and click on the ‘Program’
button. You’ll see the output of what’s happening
in the black box below, but with a bit of luck, the
BrewPi will beep a couple of times and a few
minutes later, you’ll have a programmed BrewPi.
When you update the firmware of the BrewPi,
the output console keeps you updated on
progress. It only takes a couple of minutes.
are three different kinds of bolt – two of identical
length but slightly different widths, which you’ll find
out when you try to squeeze a larger one into the
smaller holes, but you might notice the other way
around, so it’s still worth laying everything out before
you start, Similarly, there are two different kinds of nut,
although on first glance they all look identical, and the
case building consists of two separate small phases
– connecting the Arduino to the case followed by the
LCD panel we built into the shield earlier. The grey
threadless spacers are used to distance the LCD from
the edge of the case, while the threaded white spacers
are used for the Arduino. The position of the holes
through the Arduino PCB mean that it can only be
fitted onto the case one way – with the power and
USB connector along the rear edge.
As we mentioned earlier, you also have the choice
of whether to mount the OneWire board to the top
panel or mount this inside your freezer cabinet so that
the sensors plug directly into this within the freezer. As
we opted to mount it to the case, and you need to use
the provided small plastic panel (with OneWire
embossed onto its top surface, along with numbers
for each input). Two of the narrow bolts go through
the PCB, through the small plastic panel, through the
case, through a washer and finally onto a nut to make
this happen.
After connecting the Arduino to the case and
making a decision about the OneWire connection, we
now need to put everything together like a simple 3D
jigsaw puzzle. The half-circle plastic nodules are the
feet, and to get ours together, we first fitted the rear
panel. This is the one with the holes for power, USB
and the controller connectors, and after you’ve placed
it over the Arduino ports, you can hold it in by plugging
in the green ‘AT-AT’ connectors to the outside of the
case. They fit in pairs with the exception of the single
three-pin connection on one edge. The two side
panels then slid into the rear panel, followed by the top
and finally the LCD, which slid onto those to all of the
other panels to make the front. Don’t forget that many
Our first brew started at 20 degrees and lowed to 18 after
48 hours, to create the best temperature for the beer.
of these panels have a thin layer of plastic that can be
removed, along with a few squares for the joints that
may not have fallen out with the laser cutting.
Eight of the remaining screws now pull the case
together, in the same way that they did for the
Raspberry Pi case. The official instructions suggest
using a magnet to hold the nut in place, but we we
found it easier to push the bolt in until it reaches the
gap for the nut, then ease the nut into place using the
nut to make sure it doesn’t go too far and drop inside
the case (which is going to happen with the last one
anyway – stay calm and think of beer). A quick tip if
one does fall in, you can play an amusing game with
yourself and attempt to bounce the nut back out of
the same hole - it’s not that difficult but looks a little
deranged. Sensible people will loosen the bolts at one
end to separate the box enough, which is also a good
way of taking the top of the case without removing
any of the bolts. And don’t forget the washers on the
outside. They’re needed to make the bolt fit.
Loose fit
But we’d suggest maybe loosely taping the case
together for now, until you’ve been able to test out
your BrewPi with the software to ensure that
everything works. That way you don’t get doubly
frustrated by something not working and having to go
through the whole unscrewing process again. You
now need to connect the two SSR blocks to the
outputs on the shield, making sure you get the
positive cable going to the positive input and the
negative cable going t the negative input on the SSR.
These solid state relays perform a simple job, turning
the power going through the other two points either
on or off. This is used by the BrewPi to automatically
turn on refrigeration or heating. Some BrewPiers have
reverse engineered their refrigeration units and
heaters to splice these connections into the most
efficient place. We cut open the power cables to both
the freezer and the heater, took out and cut the
negative wire, and used this on other side of the power
output on both SSRs. The power output was on the
top of our SSRs, while the control inputs were in the
bottom. Make sure you get this correct and that your
wiring is safe, because you could easily create a
hazard at this step. You should also consider the
The BrewPi is brilliant at
controlling temperature.
Here’s the sensor output
after we put a bin of 50°C
water into the fridge and
asked the BrewPi to take
the temperature down to
Although not essential,
a cheap multimeter
can make testing much
easier – especially if it
makes a sound when the
two contacts connect.
This is called testing for
continuity, and it’s a great
way to make sure dodgy
soldering is working.
The algorithm that
controls the BrewPi is
complex, but you can even
fine tune this from the
Maintenance panel if you
so desire.
location of the SSRs, as they’re usually exposed and
obviously shouldn’t go anywhere near liquid.
Back on the BrewPi shield, one output to the SSR
triggers a red LED while the other triggers a blue LED,
so it’s worth getting them correctly connected as you
can then see when your device is heating or cooling.
These connections are on the backside of the shield,
not on the OneWire connector – that’s just used for
the sensors at the moment, although there’s talk of
adding a hydrometer reader to measure the alcohol
content, which is something we’d love to see.
Now stop. It’s time to admire your work. The tough
bit is over with, as the BrewPi is now built, waiting only
for a little Linux magic to bring it life. And you know all
those holes in the top of the BrewPi case? And the
weird semi circle feet on the Raspberry Pi case? They
fit together! Your Raspberry Pi should sit snugly to the
top of the case like the Boeing 747 of brewing.
Configuring devices
The very final step (we promise!), is to tell your BrewPi
exactly what you’ve got connected, and we found it
easier to start with a blank canvas. Click on ‘Device
Configuration’ button from the Maintenance panel
and you’ll see a list of devices your BrewPi thinks are
connected. The devices are the switches to control
the heating and cooling, plus the two or three sensors
you’ve got connected. If any devices appear in the
Installed Devices list, set their function (a drop-down
list on the right of each entry) to ‘None’ and click Apply.
This will move them from the ‘Installed Devices’ box to
the ‘Detected Devices’ box, from where we can now
add them as we need to. Enable ‘Read Values’ and
click on Refresh Devices. Click on the ‘Refresh Device
List’ button and enable the ‘Read Values’ check box.
This will list connected devices along with a number
to indicate what the switch or sensor is reading. You
can easily detect and check your sensors are
functioning in this way. OneWire works with unique
identifiers embedded within each device, so the device
ID is unique for each sensor, not for the BrewPi
configuration. That means if you identify which sensor
you’re going to use within your fermenting bin, you
can plus this into any of the OneWire connectors. We
checked sensor was working by plugging each in turn
and refreshing the device list to make sure a
temperature value was being read. We also identified
each sensor by heating or cooling the sensor and
wrote down which one was which.
You need two sensors for the BrewPi to work
properly. One measures the ambient temperature
within your fridge or freezer, while the other measures
the temperature within the beer. For the beer
measurement, it’s recommended you use a
‘thermowell’ to keep the sensor separate from your
beer. You also need to solve the problem of getting the
sensor cables into the fridge or freezer cavity. Some
users piggyback their wires onto any wires they can
already find going into fridge. Our approach was to
butcher an Ethernet cable – there are more than
enough cores within one of these for 2 of the sensors
– and drill a tight-fitting hole for both this cable and
the power cable for the heating unit, into the side of
the freezer. This has worked with no problems so far,
and not affected the insulation of the freezer.
Brewing your first beer
With sensors in place and the software running on
your BrewPi, you’re ready to brew. Despite the slightly
intimidating appearance of the web interface, it’s very
straightforward to use. Click on the ‘fermenting’ link
just below the BrewPi logo and you’ll be given the
option of starting a new brew. You can do this to log
the details of each brew, as well as clear the data for
the start of a new fermentation cycle. The main
display area is taken up by a graph showing the
changes in beer temperature (green) and freezer
temperature (blue), as well as the temperature outside
the fridge, although this isn’t used by its algorithms.
At the bottom, along the timeline, blue and red blocks
show when the cooling and heating was engaged.
There are three modes for fermenting your brew;
Beer Constant, Fridge Constant and Beer Profile. Beer
Constant simply keeps the beer at a specific
temperature, which you dial into the large number bar
at the bottom of the screen. Expanding on this, the
Beer Profile setting enables you to set a desired beer
temperature for each day. This is useful if you want to
try a slightly warmer environment at the beginning
and end of the fermenting cycle. When either of these
beer profiles are active, the LCD display shows the
absolute temperature as well as the temperature for
the profile. This is the target temperature for the
algorithm, and you’ll find the BrewPi will cool or heat to
nudge the temperature closer to the desired value.
The Fridge Constant setting does what it says,
keeping the temperature of the fridge at a specific
value. This might be useful for the couple of days after
you’ve bottled your beer, or put it in a cask, as you
usually have a couple of days of secondary
fermentation. But it could be equally useful for cooling
your final product for the final, essential step of
brewing beer – keeping your home-brew ready to
drink at a perfect temperature, all year round.
The world of homebrew will feel familiar – it’s full of people who
obsess over details and argue endlessly about packages.
omebrew forums across
the internet are full of
enthusiasts arguing over
every detail of the brewing
process. And we mean every
detail. Fermentation temperature
is a dark art of its own, as is the
amount of priming sugar to use
– we’ve seen simpler algorithms
explain Bézier curves in OpenGL!
As with Linux, all this data and
debate can be totally
overwhelming to the beginner. But
again like Linux, it’s worth
struggling through to the other
side. Just think of the beer.
We also see no shame in
starting small. Beer kits are perfect
for this. They can be a little pricey,
but they’ll take the pain out of your
first brew. To get started, you’ll
need some simple pieces of kit.
Here’s what we recommend:
A 25-litre fermentation bin
This doesn’t need to be absolutely
airtight, as the brewing process will
create C02, which sits on the top to
create an airlock. We drilled a hole
in the top to encase one of our
BrewPi sensors within its own well.
A similar sized pressure barrel
The pressure part is important for
the secondary fermentation
preocess, because it’s what
carbonates your beer and keeps
your beer fresh. We’d recommend
a pressure valve with a connector
for a C02 canister. These are
relatively cheap, and they’re used
to create a C02 buffer when the
pressure gets too low to push the
beer out effectively. If you don’t
want to use a pressure barrel, you
can use bottles with caps.
Just like open source software, you can create your own recipe or you can
stand on the shoulders of giants. Image credit
Everything that comes into
contact with your developmental
beer has to be free of any
harmful bacteria. Bacteria and
wild yeast kill beer over the period
it is stored, leading to feelings
similar to a hard drive failure.
A syphon and hydrometer.
The syphon is to transfer your
beer from the fermentation bin to
the pressure barrel or bottles,
while the hydrometer is to
calculate how much alcohol is in
your brew. You must measure
the gravity at the beginning and
the end of the process for this to
work – taking a measurement at
the end isn’t enough.
The biggest threats to your
beer are sanitisation, as we’ve
already mentioned, and
temperature fluctuation, which is
solved with the BrewPi. Another
tip we’ve found helpful is to cover
all threads (such as those for the
tap, the top and the valve on the
pressure barrel) with Vaseline, as
this helps to keep them airtight.
After you’ve whetted your
appetite with a beer kit or two, it’s
time to move up to replacing the
kit with your own. There are
thousands of years of experience
on the subject, and to be honest,
we’ve only just started. But a good
place to look for your first brew is a
recipe that is itself open source.
Free Beer
This is exactly what is offered at, a tested and refined
recipe for making excellent beer
that’s been released CC-BY-SA.
The ingredients list five different
types of malt, Guaraná beans for
added spice and energy and
London ale yeast. This is followed
by step-by-step instructions that
will take your beer from mash to
wort to fermentation to beer in as
little as three weeks, all in the
name of Free Beer. If you do get
around to making some, and you
have a bottle left over, you know
where to send them.

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