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Picture of The Arduino Weather Station / Thermostat
UPDATE: http://www.instructables.com/id/Temperature-and-Humidity-on-a-Graphical-LCD/

UPDATE: Add dew point calculations

I've always been interested in monitoring my local weather, and noticed the difference between what weather.com and accuweather.com think my local weather is, and what I see out the window. I also wanted better control over my heating and A/C system. As a computer and electronics nut, I've been playing with the Arduino Microcontroller, and decided to to meld my interests. So here goes the documentation on my home built solar powered weather station (always being modified, and expanded) with HVAC Control.

 
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Step 1: The Arduino

Picture of The Arduino
pico.jpg
The first step was obtaining a Arduino board. We purchased ours from hacktronics.com. After working through the tutorials on their site, I felt confident that I understood the simple scripting and connection concepts, and moved forward.

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments. - http://arduino.cc/

The Arduino requires 5v to run, and we supply this with our Pico Solar PV / Lithium battery pack.

Step 2: The LCD Display

Picture of The LCD Display

I needed the ability to display temperature, humidity, barometric pressure, and time/date, so I picked a 4 line white on blue LCD display from Hacktronics. I used their LCD tutorial to get it connected and display some sample text on the screen.

// character LCD example code
// www.hacktronics.com


// Connections:
// rs (LCD pin 4) to Arduino pin 12
// rw (LCD pin 5) to Arduino pin 11
// enable (LCD pin 6) to Arduino pin 10
// LCD pin 15 to Arduino pin 13
// LCD pins d4, d5, d6, d7 to Arduino pins 5, 4, 3, 2
LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

int backLight = 13; // pin 13 will control the backlight

void setup()
{
pinMode(backLight, OUTPUT);
digitalWrite(backLight, HIGH); // turn backlight on. Replace 'HIGH' with 'LOW' to turn it off.
lcd.begin(16,2); // columns, rows. use 16,2 for a 16x2 LCD, etc.
lcd.clear(); // start with a blank screen
lcd.setCursor(0,0); // set cursor to column 0, row 0 (the first row)
lcd.print("Hello, World"); // change this text to whatever you like. keep it clean.
lcd.setCursor(0,1); // set cursor to column 0, row 1
lcd.print("hacktronics.com");

// if you have a 4 row LCD, uncomment these lines to write to the bottom rows
// and change the lcd.begin() statement above.
//lcd.setCursor(0,2); // set cursor to column 0, row 2
//lcd.print("Row 3");
//lcd.setCursor(0,3); // set cursor to column 0, row 3
//lcd.print("Row 4");
}

void loop()
{
}


See http://www.hacktronics.com/Tutorials/arduino-character-lcd-tutorial.html for actual code as instructables breaks our include statements.

Step 3: Temperature & Humidity

Picture of Temperature & Humidity

I purchased a SHT21 Temperature Humidity sensor from MisensO.com. This chip uses the I2C protocol for communicating. I found some sample code on the net that makes it talk to the Arduino, but it outputs to the serial port back to the pc. I modified the code to output to my LCD. I now have the Temperature and Humidity showing on the LCD display.

//Tested with SHT21 Breakout from Misenso
//SHT21 pin SDA to Arduino Analog pin 4
//SHT21 pin SCL to Arduino Analog pin 5
//SHT21 pin GND to Arduino GND
//SHT21 pin VCC to Arduion 3v (not 5v)


lcd.begin(20,4); // columns, rows. use 16,2 for a 16x2 LCD, etc.
lcd.clear(); // start with a blank screen
lcd.setCursor(0,0); // set cursor to column 0, row 0 (the first row)
lcd.print("Humidity: "); // change this text to whatever you like. keep it clean.
lcd.print(humidity.GetHumidity());
lcd.setCursor(0,1); // set cursor to column 0, row 1
lcd.print("Temp in C: ");
lcd.print(humidity.GetTemperatureC());
lcd.setCursor(0,2); // set cursor to column 0, row 2
lcd.print("Temp in F: ");
lcd.print(humidity.GetTemperatureF());

See
http://arduinotronics.blogspot.com/2010/09/our-temperature-humidity-monitor-is.html for actual code as instructables breaks our include statements. You will need the LibHumidity.h library from Modern Devices for this project.

Step 4: HVAC Control

Picture of HVAC Control

Now that I know what the temperature is, I need to control my A/C and heat based on what I want the temp to be. I installed a RGB LED as a placeholder for the relays I will be installing. If the system calls for heat, it turns the LED red. If it calls for cooling, it turns the LED Blue. If it's in our comfort range, it turns green.

if (humidity.GetTemperatureF() < 60)
{
digitalWrite(RedLEDPin, LOW); // sets the Red LED on
digitalWrite(BlueLEDPin, HIGH); // sets the Blue LED off
digitalWrite(GreenLEDPin, LOW); // sets the Green LED off

}
else if (humidity.GetTemperatureF() >= 75)
{
digitalWrite(BlueLEDPin, LOW); // sets the Blue LED on
digitalWrite(RedLEDPin, HIGH); // sets the Red LED off
digitalWrite(GreenLEDPin, HIGH); // sets the Green LED off
}
else
{
digitalWrite(GreenLEDPin, LOW); // sets the Green LED on
digitalWrite(BlueLEDPin, HIGH); // sets the Blue LED off
digitalWrite(RedLEDPin, HIGH); // sets the Red LED off

}

See http://arduinotronics.blogspot.com/2010/09/our-temperature-humidity-monitor-is.html for actual code as instructables breaks our include statements.

Step 5: Current code with wiring instructions

Picture of Current code with wiring instructions

The following is the code as it exists today. I am adding a second SHT21 for indoor/outdoor measuring (means hacking a second I2C channel, as the SHT21's all have the same address, and can't exist on one channel), and I'm still waiting for my real time clock chip and barometric pressure sensor to arrive from Sparkfun.com (they arrived yesterday, and I will work on this on the weekend - 9-29-10). I migrated the project over to my new Arduino Mega 2560 (58 I/O lines), and installed the new 0021 IDE. I will edit this instructable as the project evolves.

// Connections:
// LCD pin 1 to Arduino GND
// LCD pin 2 to Arduino 5v
// LCD pin 3 (Contrast) to GND
// rs (LCD pin 4) to Arduino pin 12
// rw (LCD pin 5) to Arduino pin 11
// enable (LCD pin 6) to Arduino pin 10
// LCD pin 15 to Arduino pin 13
// LCD pin 16 to Arduino GND
// LCD pins d4, d5, d6, d7 to Arduino pins 5, 4, 3, 2

//Tested with SHT21 Breakout from Misenso
//SHT21 pin SDA to Arduino Analog pin 4
//SHT21 pin SCL to Arduino Analog pin 5
//SHT21 pin GND to Arduino GND
//SHT21 pin VCC to Arduino 3v (not 5v)

//RGB LED
//Red Cathode to Arduino pin 9
//Blue Cathode to Arduino pin 8
//Green Cathode to Arduino pin 7
//Anode to 270 ohm resistor to 5V

#include
#include
#include

LibHumidity humidity = LibHumidity(0);

LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

int backLight = 13; // pin 13 will control the backlight
int RedLEDPin = 9; // LED connected to digital pin 9
int BlueLEDPin = 8; // LED connected to digital pin 8
int GreenLEDPin = 7; // LED connected to digital pin 7


void setup()
{
pinMode(backLight, OUTPUT);
digitalWrite(backLight, HIGH); // turn backlight on. Replace 'HIGH' with 'LOW' to turn it off.

//I2C
pinMode(16, OUTPUT);
digitalWrite(16, LOW); //GND pin
pinMode(17, OUTPUT);
digitalWrite(17, HIGH); //VCC pin

//Furnace / AC Indicator
pinMode(RedLEDPin, OUTPUT); // sets the digital pin as output
pinMode(BlueLEDPin, OUTPUT); // sets the digital pin as output
pinMode(GreenLEDPin, OUTPUT); // sets the digital pin as output

}

void loop()
{
lcd.begin(20,4); // columns, rows. use 16,2 for a 16x2 LCD, etc.
lcd.clear(); // start with a blank screen
lcd.setCursor(0,0); // set cursor to column 0, row 0 (the first row)
lcd.print("Humidity: "); // change this text to whatever you like. keep it clean.
lcd.print(humidity.GetHumidity());
lcd.setCursor(0,1); // set cursor to column 0, row 1
lcd.print("Temp in C: ");
lcd.print(humidity.GetTemperatureC());
lcd.setCursor(0,2); // set cursor to column 0, row 2
lcd.print("Temp in F: ");
lcd.print(humidity.GetTemperatureF());
{
if (humidity.GetTemperatureF() < 60)
{
digitalWrite(RedLEDPin, LOW); // sets the Red LED on
digitalWrite(BlueLEDPin, HIGH); // sets the Blue LED off
digitalWrite(GreenLEDPin, LOW); // sets the Green LED off

}
else if (humidity.GetTemperatureF() >= 75)
{
digitalWrite(BlueLEDPin, LOW); // sets the Blue LED on
digitalWrite(RedLEDPin, HIGH); // sets the Red LED off
digitalWrite(GreenLEDPin, HIGH); // sets the Green LED off
}
else
{
digitalWrite(GreenLEDPin, LOW); // sets the Green LED on
digitalWrite(BlueLEDPin, HIGH); // sets the Blue LED off
digitalWrite(RedLEDPin, HIGH); // sets the Red LED off

}
}

delay (20000);
}



See http://arduinotronics.blogspot.com/2010/09/our-temperature-humidity-monitor-is.html for actual code as instructables breaks our include statements.

Step 6: Arduino Clock Module

Picture of Arduino Clock Module
ds1307.jpg

We finished the Arduino Time & Date functions using the Sparkfun DS1307 I2C RTC module, a 2 line LCD, and the Arduino Duemilanove.  There are four connections from the DS1307 to the Arduino:


//pin SDA to Arduino Analog pin 4
//pin SCL to Arduino Analog pin 5
//pin GND to Arduino GND
//pin VCC to Arduino 5v

To set the time, edit the following section in the code with the correct time and date,

// Change these values to what you want to set your clock to.
// You probably only want to set your clock once and then remove
// the setDateDs1307 call.
second = 0;
minute = 42;
hour = 9;
dayOfWeek = 1;  //Sunday
dayOfMonth = 3;
month = 10; //October
year = 10;

and temporarily remove the // from the following line:

//setDateDs1307(second, minute, hour, dayOfWeek, dayOfMonth, month, year);

Upload your code to the Arduino, then put the // back in the above line, and upload again.

The complete code and wiring are posted at http://arduinotronics.blogspot.com/2010/10/ds1307-real-time-clock-working.html

cprocjr4 years ago
I was thinking about doing something like this, but with wind speed and rainfall as well. Thanks for the instructable! It'll probably help a lot when I finally get around to building mine.
sspence (author)  cprocjr4 years ago
I'll eventually get those functions in there, probably by sniffing the wireless feed from a lacrosse weather station. easier than making a anemometer and rain gauge.
cprocjr sspence4 years ago
I thought about making a anemometer and rain gauge, and I've even planned them out, but I don't want to take the time to actually make them. So instead, I just bought them from sparkfun: http://www.sparkfun.com/commerce/product_info.php?products_id=8942

I'll post an instructable once they arrive at my house and I've programed my arduino!
gdsmit1 cprocjr2 months ago

I know this was quite a while ago. But did you get that SparkFun weather kit? If so, what do you think of it?

sspence (author)  gdsmit12 months ago

We did. It's up and flying. I didn't think it would hold up, as it appears fragile, but after a year or so, it's still going strong. Need to publish the code for that.

gdsmit1 sspence2 months ago

Cool, nice to know. The "arms" that hold the anemometer and vane look kind of delicate to me.

Robotix_au9 months ago

Couple of quick questions, is it impossible to use the Arduino to keep time.... (I was thinking of using pulseIn function at the start/end of the loop to keep time...)

So if the RTC is essential can you just plug it into 5 consecutive Arduino pins instead of dealing with so much wiring?

There exists an Arduino Time library http://playground.arduino.cc/Code/Time
But this will not work if running on external power and not connected to the computer of course.

When I just started with Arduino, I attempted to write a clock code https://docs.google.com/document/d/1nSeXLC3vC2sNe9...
There was a decent amount of drift over a few hours, but it was still pretty cool. Again, I did this when I just started with Arduino/programming so it's definitely not the best thing around. You could probably find some better stuff if you just Googled, "Arduino clock" or something like that.This is something I found http://www.instructables.com/id/Make-an-accurate-A... Haven't looked at it much though.

Secondly, in my code, I kept time using the millis() function. You would probably have better luck using interrupts.

Good luck

sspence (author)  ohoilett8 months ago
If you look at my other instructables, and projects at http://arduinotronics.blogspot.com you will find network based time clients, gps based, and pc set ds1307 (no need to stay connected) projects.

Thanks pal!

I will definitely look at those links!!, Personally I am all about doing more with less, and this is up my alley!

Cool. I'm interested to see how your project turns out. Good luck.

sspence (author)  Robotix_au9 months ago
the rtc uses two datalines (a4 and a5) in addition to power and ground. you can't just plug the rtc into the arduino, as the pin connections will not line up.

Hmm... I think you can, instead of GND you just digiWrite(pin LOW) and instead of 5V you digiWrite(Pin HIGH)... I know its not best practice but it does seem to work seamlessly

Have a look at an example with an Ultrasonic sensor:

https://www.youtube.com/watch?v=pdIUNHps-5s

sspence (author)  Robotix_au9 months ago

sda and scl are reversed on this module, so you can't. you'll need to find another module. do you really want to waste your analnog ports defining them as power and ground?

Good point, I guess that depends on what the circuit needs, I really like what you built... especially that its self powered. I just bought some 1W panels + lipo batteries to see if I can build similar circuits.

oukolova3 years ago
Hi! We launched a new project of weather map layer for OpenStreetMap http://openweathermap.org/. It public project that collects data from more than 20,000 meteorological and weather stations around the world. The more weather stations connect the more precise weather data we provide to people. All collected weather data are provided under CC-BY-SA 2.0.You can connect your weather station to the service http://openweathermap.org/connect
schuguy3 years ago
I'm wondering if you ever added the relays and the outdoor temp and humidity.
sspence (author)  schuguy3 years ago
I added the SSR's, directly addresses by an output pin. This allows control of ac devices, up to 660v and 150 amps, depending on the SSR, with an optically isolated 5v input.

I also added the outdoor temp and humidity.
bkik4 years ago
Does/Can this setup also log data for an extended period of time (say three months)? I'd love to be able to drop this in an off-grid spot and have it continuously working for me; just check on it every few weeks and dump data to a laptop. Or even better, find a way to dump the data to a server so I can visit it and dl it from anywhere. Would this work?
the naP bkik3 years ago
You can use Gobetwino (http://www.mikmo.dk/gobetwino.html) to log the serial output to a file on a computer connected to the Arduino. If you have a machine that is always on, this is a pretty good way to go, as it doesn't require any additional hardware.

If not, one of the listed options is pretty nice, especially the storage shields.
sspence (author)  bkik4 years ago
This is very cool. When you are ready to integrate forecasted weather for your location to make your HVAC controls predictive, let me know, as we can provide and even integrate your sensor data if we can get at the output.
roland9854 years ago
What OS are you using? I am using Xubuntu 11.04
sspence (author)  roland9854 years ago
Ubuntu 11.04 and Windows Vista.
frenzy4 years ago
I said to myself 6 months ago how i should do this project, good job getting to it first!
sspence (author)  frenzy4 years ago
Wait till I get the relays installed and it turns on my a/c and furnace when necessary :-) Should have barometric pressure and time / date functions (for setback thermostat capability) working next weekend. Running out of IO lines, will need a expander. http://www.embedds.com/arduino-i2c-expansion-io/
Yea, I have a heat pump, and one of the efficiency tweaks is to not turn on the auxiliary heating when the outside weather is above 0 degF

I might reuse some of this to add that feature to my "dumb" digital thermostat, which will do a call for "aux heat" if it kicks on and the room temp is 2 degF below the set point.
renegade4284 years ago
nice job! how much did it cost you about?
sspence (author)  renegade4284 years ago
About $70 or so.
odiekokee4 years ago
That is awesom. Now if i can figure out how to make it send signals back over morse code or something without RF i'll be set.
sspence (author)  odiekokee4 years ago
We both remember the modulated lightbeam kits of the late 70's.
kikiclint4 years ago
I think one of your wires on your lcd is loose in that first picture. Mine does the funny wierd symbols if a wire temporarily becomes disconnected.
sspence (author)  kikiclint4 years ago
naw, it was a errant carriage return (println instead of print), carried over from the serial output of the original code snippet.