In Part 3 of our project – home weather station with Arduino board, comes the most interesting part, at least for me – connecting the sensors and data extraction.
To see working and reporting stations made with setup similar to mine, check out Chris’ and Alan’s pages.
Ok. Lets continue:
The first step is to plug the Ethernet shield in to the main board – gently insert the board on top of the Arduino – nothing special.
* Note – if the station is going to be in a box, put the sensor cable as far away from the board as possible. The main chip of Ethernet shield can get quite hot 42-43 degrees at 22 degrees ambient temperature, which can seriously affect the data.
Once we have the basic modules connected:
- Connect BMP180 pressure and temperature sensor:
- SCL to analog pin 5
- SDA to analog pin 4
- VDD pin to 5 volts
- GND to ground
- Connect the SHT75 temp and humidity:
- Clock (Pin1) digital pin 2
- Data (Pin4) digital pin 3
- Vcc (Pin2) to pins with 5V
- GND (Pin3) to ground.
- For DHT11 sensor linking use the same order
- Connect the rain sensor:
- A1 analog pin 1
- Vcc pins to 5 volts
- GND to ground.
Sorry I didn’t took any photos when I made the project, but my test version of the staton looked similar to this one:
Once we connect all the sensors the only thing that is remaining is to write the code. Some sensors require a library, for example BMP180 requires one, which can be downloaded from HERE.
Below is code that I wrote with comments about it.
What the code does, is printing the results of the sensors on the serial monitor (Tools > Serial Monitor), as well as displaying the data trough a Web server to local IP address, on minimalist look web page, so that you can style it later.
#include <Wire.h>
#include <SPI.h>
#include <Ethernet.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP085_U.h>
#include <Sensirion.h>
/*
Connections [BMP180]
===========
Connect SCL to analog 5
Connect SDA to analog 4
Connect VDD to 5V DC
Connect GROUND to common ground
Connections [SHT75]
===========
Connect Clock(Pin1 - White) to 2 (digital)
Connect Data(Pin4 - Yellow) to 3 (digital)
Connect Vcc (Pin2 - Red) to 5V DC
Connect GND (Pin3 - Black) to common ground
*/
/*Sensirion SHT75 Constants*/
const uint8_t dataPin = 3; // SHT serial data
const uint8_t sclkPin = 2; // SHT serial clock
const uint32_t TRHSTEP = 5000UL; // Sensor query period
const int rainMin = 0; // rain sensor minimum
const int rainMax = 1024; // rain sensor maximum
Sensirion sht = Sensirion(dataPin, sclkPin);
uint16_t rawData;
float temperature;
float humidity;
float humidex;
float dewpoint;
byte measActive = false;
byte measType = TEMP;
unsigned long trhMillis = 0; // Time interval tracking
/*Sensirion SHT75 Constants END*/
Adafruit_BMP085_Unified bmp = Adafruit_BMP085_Unified(10085); //BMP180 code
/*OneWire ds(7); // on pin 2 (a 4.7K resistor is necessary)*/
float celsius = 0; // global temperature variable
float pressurekPa = 0; //global pressure variable
//Ethernet setup >
byte mac[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
};
IPAddress ip(192, 168, 1, 200);
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
EthernetServer server(80);
void setup(void)
{
Serial.begin(9600);
/*SHT75 SETUP:*/
delay(15); // Wait >= 11 ms before first cmd
// Demonstrate blocking calls
sht.measTemp(&rawData); // sht.meas(TEMP, &rawData, BLOCK)
temperature = sht.calcTemp(rawData);
sht.measHumi(&rawData); // sht.meas(HUMI, &rawData, BLOCK)
humidity = sht.calcHumi(rawData, temperature);
dewpoint = sht.calcDewpoint(humidity, temperature);
logData();
/*SHT75 SETUP END*/
/* Ethernet config */
Ethernet.begin(mac, ip);
server.begin();
Serial.print("server is at ");
Serial.println(Ethernet.localIP());
/* Initialise the BMP180 sensor */
if(!bmp.begin())
{
/* There was a problem detecting the BMP180 ... check your connections */
Serial.print("Ooops, no BMP180 detected ... Check your wiring or I2C ADDR!");
while(1);
}
}
void loop(void)
{
/* Temp readings: */
/*SHT75 loop: */
unsigned long curMillis = millis(); // Get current time
// Demonstrate non-blocking calls
if (curMillis - trhMillis >= TRHSTEP) { // Time for new measurements?
measActive = true;
measType = TEMP;
sht.meas(TEMP, &rawData, NONBLOCK); // Start temp measurement
BMP180(); // Pressure measurement
trhMillis = curMillis;
}
if (measActive && sht.measRdy()) { // Note: no error checking
if (measType == TEMP) { // Process temp or humi?
measType = HUMI;
temperature = sht.calcTemp(rawData); // Convert raw sensor data
sht.meas(HUMI, &rawData, NONBLOCK); // Start humidity measurement
} else {
measActive = false;
humidity = sht.calcHumi(rawData, temperature); // Convert raw sensor data
dewpoint = sht.calcDewpoint(humidity, temperature);
//humidex code:
float h,e; //humidex and other
e = 6.11 * exp(5417.7530 * ((1/273.16) - (1/(dewpoint + 273.15))));
h = (0.5555)*(e - 10.0);
humidex = temperature + h;
logData();
}
}
/*SHT75 loop end*/
/* Web server: */
EthernetClient client = server.available();
if (client) {
Serial.println("new client");
// an http request ends with a blank line
boolean currentLineIsBlank = true;
while (client.connected()) {
if (client.available()) {
char c = client.read();
Serial.write(c);
// if you've gotten to the end of the line (received a newline
// character) and the line is blank, the http request has ended,
// so you can send a reply
if (c == '\n' && currentLineIsBlank) {
// send a standard http response header
client.println("HTTP/1.1 200 OK");
client.println("Content-Type: text/html"); // text/html
client.println("Connection: close"); // the connection will be closed after completion of the response
//client.println("Refresh: 5"); // refresh the page automatically every 5 sec
client.println();
//client.println("<!DOCTYPE HTML>");
//client.println("<html>");
// output the data
client.print(temperature);
client.print(" ");
client.print(humidity);
client.print(" ");
client.print(pressurekPa);
client.print(" ");
client.print(dewpoint);
client.print(" ");
client.print(humidex);
client.print(" ");
client.print(analogRead(A1));
//client.println("<br />");
//client.println("</html>");
break;
}
if (c == '\n') {
// you're starting a new line
currentLineIsBlank = true;
}
else if (c != '\r') {
// you've gotten a character on the current line
currentLineIsBlank = false;
}
}
}
// give the web browser time to receive the data
delay(1);
// close the connection:
client.stop();
Serial.println("client disconnected");
}
}
void BMP180() {
delay(1500);
/* Get a new sensor event */
sensors_event_t event;
bmp.getEvent(&event);
/* Display the results (barometric pressure is measure in kPa) */
if (event.pressure)
{
/* Display atmospheric pressue in kPa */
Serial.print("[BMP180]Pressure: ");
Serial.print(event.pressure / 10);
pressurekPa = event.pressure / 10;
Serial.println(" kPa");
/* First we get the current temperature from the BMP085 */
float temperature;
bmp.getTemperature(&temperature);
Serial.print("[BMP180]Temperature: ");
Serial.print(temperature);
Serial.println(" C");
/* Then convert the atmospheric pressure, and SLP to altitude */
/* Update this next line with the current SLP for better results */
float seaLevelPressure = 1022 /*SENSORS_PRESSURE_SEALEVELHPA*/;
Serial.print("[BMP180]Altitude: ");
Serial.print(bmp.pressureToAltitude(seaLevelPressure,
event.pressure));
Serial.println(" m");
Serial.println("");
}
else
{
Serial.println("Sensor error");
}
}
void logData() {
Serial.print("[SHT75]Temperature = "); Serial.print(temperature);
Serial.print(" C, Humidity = "); Serial.print(humidity);
Serial.print(" %, Dewpoint = "); Serial.print(dewpoint);
Serial.println(" C");
Serial.print("Humidex: ");
Serial.println(humidex);
Serial.print("Water Level: ");
Serial.println(analogRead(A1));
}
The above code will make a Web server on 192.168.1.200, where on a single line you will see the data from all sensors.
These data can now be taken in order to generate graphics or store it inside a file or whatever you are most comfortable with. I personally use Linux machine that draws graphics using munin software (based on rrdtool). There are thousands of solutions for drawing graphics; you just have to look at the options.
And that’s it.
