How to make Weather Station Video
Take back the power of weather forecasting from your local weatherman
and begin your own foray into the world of amateur meteorology and
citizen science with your very own DIY weather station and data logger.
In this Instructable, I'll show you how I designed and built a weather
station around the Intel Edison board and a handful of sensors. With
little more than a few parts from the hardware store, and heaps of
screws I'll take you step by step through the design and assembly
process. Let's begin!
Step 1: Parts and Materials
Intel Edison with Arduino breakout board
altimeter
dust sensor
humidity sensor
anemometer
light sensor
solar panel
real-time clock
solar LiPo battery charger
5V boost converter
9V boost converter
4400 mAh LiPo battery
8 GB micro SD card
5mm green LED
5mm blue LED
(2x) 1K resistor
(capacitor for dust)
(resistors for dust)
M-F extension cables
22 gauge wire
26 gauge ribbon cable
female-male jumper wires
10-24 screws
(12x) 1"
(8x) 1.5"
(8x) 2"
(28x) 10-24 nut
(8x) 1/4-20 screws
(8x) 1/4-20 lock nut
(4x) 2-56 x 1/2" screw
(4x) 2-56 x 1/2" nut
18" dowel rod (1" diameter)
3/4"x60" EMT conduit
3/4" EM Flex coupling
3/4" shaft coupler
3/4" shaft to thread adapter
3/4" floor flange
3"x40" galvanized vent tube
3" vent bonnet
3" vent strap
water level
(3x) conductor strap
(3x)
tent stakes
paracord (25ft)
(2x) 24"x36"1/4" plywood sheet
12"x12"x1/8" clear acrylic sheet
double stick tape
wood glue
black spray paint/primer
silicone caulk
Step 2: System Design
What Makes a Weather Station?
At
it's most basic, a weather station is any system that gathers
environmental/climate data. While more useful as a network, I designed a
single node as this would be a practical introduction to weather data
gathering. I wanted the system to collect and store a handful of
metrics: wind speed, light, humidity, temperature, pressure, and air
quality. The weather station has a lot of distinct parts and goals; to
simplify the design process I broke it down into three distinct parts:
electrical, hardware, and software. Here's a brief breakdown of each:
Electrical
I
wanted to the make the weather station low maintenance, so I decided to
make it solar powered with a built-in beefy (by embedded project
standards) Li-Po battery pack. This setup allows the station to run
remotely and, barring excessive daily darkness, a reasonably endless run
time. The Edison board has very low current draw and Bluetooth and WiFi
radios should I want to add wireless connectivity later on. The
electrical design and components are discussed in depth on the following
step.
Hardware
The main body consists
mostly of parts available from a hardware store. A conduit tube forms
the core of the body and a solid mounting point for the other
components. A series of laser cut panels form the headpiece for mounting
a couple of the sensors, and a solid mount place for the solar panel
and power electronics. A large galvanized ventilation tube provides a
weather resistant housing for the the additional sensors that need to be
"exposed" to the elements for proper data collection. The hardware
design is explained more in-depth on step 5.
Software
In
order to minimize the amount of time I spent writing code, I chose
sensors that were already well documented and had either libraries or
simple analog interfaces. The actual software is the Wiring language
written in Intel's custom Arduino IDE. Developing with Arduino style
syntax allowed me to work quickly, since it is my go to environment for
interactive projects. The software is discussed more in detail on step
10.
Step 3: Electrical Design
In order to speed up the build process, I
chose sensors that came on breakout boards with the standard 2.54
millimeter pin out. The system is built using point-to-point wiring with
only a handful of splices using as many temporary male to female header
connections as possible to keep soldering to a minimum. Here's a
breakdown of the different electrical systems. The illustration above is
a hybrid block diagram/schematic since nearly all of the electronics
are complete modules (the attachment is the Sharp sensor data sheet).
Power
The
power system for the weather station is entirely self-contained (no
external charging ports!). A small solar panel feeds roughly 6 volts at
around 330 mAh (on a bright day) into the DC input pins of an Adafruit
solar Lithium Polymer battery charger. The charger has two JST sockets:
one for the battery and the other to the load. The entire system draws
roughly 300 mAh, so it should have plenty of power to last through a
long night before charging again during the day. The ground pin from the
load connection on the charger are connected directly to system ground,
with the positive output pin connected to a nice slide switch. The
output of the slide switch has two connections (still at ~3.7) from the
battery) with one connection to the VIN pin of the 5V step-up converter
and the other to the VIN pin of the 9V step-up converter. Although the
9V out of the step-up converter could power both the VIN pin of the
Intel Edison Arduino breakout board and the Anemometer (which is spec'd
to run at 7-24V), regulating it back down to 5V would be wasteful, so I
decided to use the separate 5V supply. The 5V supply is connected via a
spliced micro USB cable to the IEABB, which then provides a nice 2.54 mm
pin-friendly female socket for providing external 3.3V and 5V
connections for the sensors.
Control
The
Intel Edison is the main controller for the system. I decided to use the
Arduino-style breakout board as it greatly simplifies wiring to the
Edison and provides a micro SD card socket on board. The breakout board
allows easy connection to the analog sensors and makes it tirivial to
connect to the I2C and SPI ports.
I/O
Although
I'm gathering six points of data, I only needed five sensors. I used an
Anemometer that provides a nice low voltage analog signal that is
proportional to wind speed. An altimeter breakout provides me with both
temperature and pressure values over I2C. I used a tiny analog humidity
sensor, which combined with the temperature from the altimeter, allowed
me to calculate relative humidity. The light sensor is a TSL2561 which
will allow me to measure a broad range of values in lux and communicates
them over I2C as well, saving a couple pins. A Sharp optical dust
sensor provides an analog voltage proportional to the concentration of
particulate matter in the air. A real-time clock is connected to the
Edison via SPI for timestamping the sensor data. An LED confirms the 5V
converter is working properly. Lastly, an LED is connected to an Edison
digital pin to allow it to communicate the system status.
The only
real human "input" is the power switch. I wanted to keep holes in the
enclosure to a minimum as this would increase the chances of water
seeping in, so there is no user input from a hardware standpoint. The
weather station is meant to be left alone for long periods of time, so
any meaningful configuration should be done in software before the
station is deployed outside.
Step 4: Electrical Assembly
Power System
The
power wiring is fairly strait forward. The wires are all within 22 to
28 AWG since the total current draw should never exceed 500 mAh. The
boost converters come with screw terminals to allow strong, yet easily
removable power connections. A micro USB cable is split for easily
powering the Edison board. Due to the nature of the power design on the
Edison's Arduino breakout, it's important to feed power via the USB port
and not directly via the 5V out socket.
Sensors and I/O
I
stripped and tinned the power wires of the anemometer to make them more
agreeable in the screw terminal. I added a male header to the analog
signal pin in order to allow direct plugging to the Edison breakout
board. For the altimeter I made an extension cable with a female header
and a few strands of ribbon cable. I attached the altimeter, dust
sensor, and humidity sensor to what I decided to call the sensor pod.
The pod provides a secure vertical mounting position for the dust sensor
and allows them to be removed if necessary. I tried to minimize the
wires coming from the pod by combining GND and VCC pins. I extended the
wires from the sensor pod by about two and a half feet and wrapped them
with a cable sheath to make them more compact. I terminated the sensor
pod wires in male headers for direct connection to the Edison board. I
connected the real-time clock with unmodified extension wires since it
will rest inside the main case with the Edison board.
Step 5: Hardware Design
I
designed the weather station in a mix of Adobe Illustrator an Autodesk
Fusion 360. I built the 3D model first, and then exported the profiles
of the body plates from Fusion as vector files (attached above). I was
able to use these for my 2D layout in Illustrator in order to fit
everything withing the bounds of two 24"x36" sheets. Nearly all of the
parts were laser cut from 1/4" plywood, the exception being a clear 1/8"
acrylic "porthole" in order for the light sensor to be properly exposed
to the sun, but not the elements. Here are the main hardware components
of the unit:
Base Mount
The base of the
weather station consists of a wooden dowel that is sanded down to a
point; forming a stake that makes for a secure way to plant the center
of the station about 14" in the ground. The station is rather tall and
top heavy, so I designed holes angled 120 degrees around the center of
the station, allowing the attachment of rope as guy lines in order to
stabilize the station. Ordinary paracord rope ties eye bolts mounted in
the holes to tent stakes in the ground.
Tube Vent
I
needed a way to expose the altimeter, humidity sensor, and dust sensor
to air without allowing any contact with water or debris. Normally,
weather stations use a
Stevenson screen,
but I wanted to try another design. In order to induce some amount of
air flow around the dust sensor, I enclosed the sensor pod in a 3"
diameter ventilation tube. As the air in the tube warms, it will rise
creating a convection current that pulls air and particulate up through
the grate at the base of the tube, and out the vent "bonnet" which is
angled to keep water out.
Anemometer Mount
The
conduit attaches via a threaded couple to a mounting flange to the top
plates. The doubled-up plates form the base for the anemometer and the
eye bolts. The flange and anemometer attach via four 1/4-20 screws and
lock nuts. These are a little overkill, but the holes for these pieces
are quite large. Two square holes allow the attachment of four angled
arm pieces, which, when doubled up, can be slotted in and screwed with a
10-24 x 1" screw.
Main Enclosure
The
angled arm pieces are bent down and attach to the main enclosure plate
via four square holes in the main enclosure plate, fastened with four
more 10-24 screws. This tilt helps keep water and debris from piling up
on the panel and dripping off the front. The top of the plate provides
holes for mounting the solar panel and light sensor. On the rear of the
panel stacked ribs of wood form an enclosure for housing the Edison
board and power system.
Step 6: Base Assembly
I
made the stake for the base by sanding the stake end down to a point. I
then sanded the other end to narrow the diameter of the dowel to fit
snugly within the conduit and coupler. Once sanded down I slide the
coupler down onto the narrow edge, followed by the main conduit tube.
The camping stakes already had convenient holes in their heads for
attaching the para-cord guy wires. I cut mine to 7ft lengths and tied
them to the eye bolts.
Step 7: Tube Mount
The
tube assembly came together fairly quickly and largely consists of two
rectangular plates of plywood painted black. I fastened the main plate
to the conduit with three zip ties. I then attached the three vent
straps around the main tube and secured them with six 1" long 10-24
screws. I mounted the level on the small wooden plate opposite the
conduit and fastened it with four 2" long 10-24 screws. With the tube
assembly mostly complete, I then dropped in the sensor pod and fished
the cable through the top of the bonnet and mounting it on the vent top.
Step 8: Anemometer Mount
I
bolted the Anemometer to the edge of the two plates to keep them
aligned with four 1" 1/4-20 screws and pulled its wires through the hole
bringing underneath the top assembly. I then attached the threaded
flange with four more 1/4-20 screws. I fastened the eye bolts into place
around the flange and twisted them out 120 degrees. I then popped in
the arms for attaching the main case and secured them with 1" 10-24
screws each.
Step 9: Main Enclosure Assembly
I
began assembling the main enclosure by screwing in the power switch and
LED holders. I then slid the sensor pod, solar, and anemometer wires
into the three holes at the top of the enclosure cover before I filled
them in with silicone-based caulk. When it came to caulking, I had a
simple philosophy: do it everywhere. Any hole or edge that opened up was
caulked. If I couldn't permanently seal an edge, I laid a bead down in a
ring to form a gasket, which I needed to do this for the case plate and
light sensor port hole.
Step 10: Software: Configuring the Edison
The
complete Arduino sketch for the Edison is attached above.
The necessary libraries are also zipped up nicely as well. You’ll need
to
unpack everything and pop it into your Libraries folder first. I also
needed to configure the MUX on the breakout board to support SPI. You
can read about that configuration process on the
Emutex Labs website.
The
program retrieves and organizes the weather data in a series of
independent functions, so you're not tied to the same sensors I used if
you'd like to easily modify the sketch I wrote. The main functions are
as follows:
int getWindSpeed(boolean whichSpeed)
returns wind speed in MPH or KPH
int getAirQuality()
returns air quality in terms of parts per
million
int getLightLevel()
returns light level in LUX
int getTemperature(boolean whichScale)
returns temperature in degrees Celsius or
Fahrenheit
int getHumidity(float outsideTemperatureCelsius)
calculates the relative humidity
int getPressure(){
returns pressure in inches
The
Edison gathers this data every 15 minutes and appends it to a .txt file
on the SD card. The data is organized in a simple ASCII string in a
format inspired by the NMEA syntax output by GPS receivers. Here is a
sample string with added spaces for reading clarity:
$ D6 M4 Y2015 H12 M45 L100 H50 W10 P10 A40 T72 \r \n
Each
string begins with a '$' character and is immediately followed by the
day, month, year, hour, minute, light level, humidity percentage, wind
speed, pressure, air quality, and temperature. The
loadSensorDataToCard() function terminates each string with a carriage
return and line feed making it much easier to read the raw .txt file
without any elaborate parsing.
