The MagPi - July 2018

raspberrypi.org/magpi May 2018 79

Feature

raspberrypi.org/magpi July 2018 79

KEEP IT DRY

Find two waterproof enclosures: one
larger one for the Pi and the breadboard
or HAT, and another smaller one for the
BME280 sensor. The larger box should
have a couple of holes for the RJ11 cables
connecting the wind and rain sensors,
and for some long wires to the BME280.
If using the recommended enclosures
(see p70), you can use this 3D-printable
mount (magpi.cc/aadkGv) to secure the
Raspberry Pi inside the larger box, and
this one (magpi.cc/rGSAQc) to hold the
BME280 sensor in the smaller one.

STEP 2

SEAL IT UP
Use short self-tapping screws to secure
the mounts into the holes and/or
grooves at the back of the larger box.
In order to get representative readings
for ambient temperature and humidity,
air needs to circulate around the BME280

STEP 1

You should now have a working

weather station prototype on a

breadboard. For a more robust,

long-term installation, or if you

don’t have room for a breadboard

in your enclosure, you can construct

a weather station HAT (hardware

attached on top) for your Pi. This

will involve some soldering – if

you’ve never soldered before,

Raspberry Pi has a great resource

plus video tutorial to get you started:

magpi.cc/VKGfig.

Note that to really be able to call it

a HAT, your board should include a

programmed EEPROM. The Adafruit

Perma-Proto HAT kit does come as

a variant with an EEPROM, so this

is definitely something you could

do, although we aren’t covering

the procedure in this guide. A

good place to start is this GitHub

repository (magpi.cc/ILpFCS), or

this article (magpi.cc/iAEnXI).

If you want to turn the

components into a HAT, then

follow these instructions:

magpi.cc/INdatp.

BUILD A WEATHER STATION

sensor. Remove both hole covers from

one side of the smaller box. You can then

pass the wires for the sensor up through

one hole. Make sure you mount this box

outside with the holes facing downwards

so that rain cannot enter this way.

Use waterproof nylon cable glands to

prevent moisture entering the enclosure

through the holes used for the cables.

STEP 3

PLUG THE HOLES

The larger recommended enclosure has

holes on all four sides that are sealed

with rubber plugs. Use three of these

holes along the bottom of the box to

provide an escape route for your cables.

Use an M16 cable gland in each of the

two outer holes and pass the cable for

the rain gauge through one and the cable

for the wind sensors through the other.

Use the larger M20 gland for the

centre hole and feed the power cable,

DS18B20 probe, and the wires for the

BME280 sensor through.

STEP 4

CRACKIN’, GROMMET

The hole in the M20 is quite large, so you

should pad the cables to ensure a tight

fit. A 3D-printable grommet is available

at magpi.cc/PrfCnV. Use two grommets

rotated at 180 degrees to each other so

that there is no gap all the way through.

STEP 5

MOUNTED OUTSIDE

You could mount your station on a wall,

rooftop, fence, or even on a plumbing

pipe stuck in the ground. The larger box

can be installed inside, to help keep it dry

and allow easier connection to power and

networking. However, the various cables

for the external sensors (rain gauge, wind

vane, anemometer, and BME280) will

then all need to be routed inside, so this

may involve a bigger hole in an external

wall. Mounting everything outside means

you only have to supply power to the

weather station (assuming you are using

wireless connectivity for data transfer).

It is not possible to provide specific

instructions for mounting your

station, as the exact method will

depend on your particular location

and environment. However, here are

some tips for a couple of aspects

of the process that should help you

get started:

• Installing your Weather
  Station outside: wind sensors
  (magpi.cc/Pxbabi).


• Installing your Weather Station
  outside: connecting to WiFi
  (magpi.cc/jujoYP).
  You may not be able to find an ideal
  location. Perhaps trees block the
  wind, or the rain gauge is partially
  sheltered by an overhang. Don’t
  worry, just install your weather
  station anyway.


• The rain gauge needs to
  collect rain.


• The anemometer and wind
  vane need to be in the wind.


• The smaller BME280 box
  needs to breathe – try to avoid
  situating it in direct sunlight.


• The weather station needs to
  be connected to power, and to
  a network (wirelessly or via an
  Ethernet cable).