Arduino Meter Reader

I’ll post soon about my latest purchase – an Arduino and Wifi Shield. The reason I purchased this little toy was to read the impulses from our meter and upload the results to PVOutput. Yeah, I know… sad or what… but when you’re in software integration, it’s oddly good fun and allowed me to see what these Arduino things are like + it might save me money in the future.

It took a few iterations to get a working program which would send results to PVOutput and wasn’t originally as planned. Due to a lack of a clock on the Arduino, there’s a piece of software on my server which receives a post request from the Arduino, adds the date and time and then sends the result on to PVOutput.

The Server script is relatively straight forward. Receive a post request, get the date and time, create the curl request and then send it.

pvoutput-post.php

<?php

$dte = date('Ymd');
$tme = date('H:i');

//echo "Watts Consumed " . $_POST["w"] . " " . $dte . " " . $tme;

$url = 'http://pvoutput.org/service/r2/addstatus.jsp';

$import = $_POST["w"];
$myvars = 'd=' . $dte . '&t=' . $tme . '&v4=' . $import;

//echo "Post Data: " . $myvars;

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $myvars);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('X-Pvoutput-Apikey: REPLACE THIS',
                                        'X-Pvoutput-SystemId: REPLACE THIS'));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_exec($ch);

?>

The program is the one running on the Arduino. Every minute (or defined interval), the number of impulses from the meter will be used to calculate the watt hours over the time period. This result is then posted to the server for upload.

#include <SPI.h>
#include <WiFi.h>
#include <WiFiUDP.h>

///////// CHANGEABLE VALUES /////////

double multiplier = 1.25;

char ssid[] = "CHANGE THIS";
char pass[] = "CHANGE THIS";

char pompeii[] = "CHANGE THIS FOR IP ADDRESS OF SERVER";
int pompeiiPort = 80;

float minutesBetweenCalls = 1;

///////// CHANGEABLE VALUES ABOVE /////////

int status = WL_IDLE_STATUS;

WiFiClient pompeiiClient;
char pompeiiService[] = "/pvoutput-post.php";

unsigned long impulseCount = 0;

unsigned long lastTimeUploaded = millis();

boolean interruptAttached = false;

unsigned long millisecondsPerMinute = 60000;
unsigned long minutesInHour = 60;
unsigned long timeBetweenCalls = minutesBetweenCalls * millisecondsPerMinute;

void setup() {
  Serial.begin(9600);
  connectToWiFi();
}

void connectToWiFi()
{
  // attempt to connect to Wifi network:
  while ( status != WL_CONNECTED) {
    Serial.print("Attempting to connect to WPA SSID: ");
    Serial.println(ssid);
    // Connect to WPA/WPA2 network:    
    status = WiFi.begin(ssid, pass);

    delay(5000);
  }

  Serial.print("Connected to the network");
  printWifiData();
}

void loop() {
  addFlashInterrupt();

  //getTimeFromPompeii();
  if (isTimeToUploadData())
  {
    Serial.println("Uploading data");
    sendResultsToPompeii();
  }
}

void addFlashInterrupt()
{
  if (!interruptAttached)
  {
    interruptAttached = true;
    Serial.println("Attaching interrupt on pin 3");
    attachInterrupt(1, flash, FALLING);
  }
}

boolean isTimeToUploadData() {
  unsigned long time = millis();

  if( (time - lastTimeUploaded) >= timeBetweenCalls) {
    Serial.println("Time to upload");
    lastTimeUploaded = time;
    return true;
  }
  return false;
}


void printWifiData() {
  // print your WiFi shield's IP address:
  IPAddress ip = WiFi.localIP();
  Serial.print("IP Address: ");
  Serial.println(ip);
}

/* Handles the interrupt flash logic */
void flash() {
  impulseCount++;
}

void sendResultsToPompeii() {
  Serial.println("sendResultsToPompeii");

  int watts = calculateWattsAndResetFlashes();
  String postData = "w=" + String(watts);
  Serial.println(postData);

  if (pompeiiClient.connect(pompeii, pompeiiPort)) {
    Serial.println("connected to pompeii");
    // Make a HTTP request:
    pompeiiClient.print("POST ");
    pompeiiClient.print(pompeiiService);
    pompeiiClient.println(" HTTP/1.1");
    pompeiiClient.print("Host: ");
    pompeiiClient.print(pompeii);
    pompeiiClient.print(":");
    pompeiiClient.println(pompeiiPort);
    pompeiiClient.println("Accept: text/html");
    pompeiiClient.println("Content-Type: application/x-www-form-urlencoded; charset=UTF-8");
    pompeiiClient.print("Content-Length: ");
    pompeiiClient.println(postData.length());
    pompeiiClient.println("Pragma: no-cache");
    pompeiiClient.println("Cache-Control: no-cache");
    pompeiiClient.println("Connection: close");
    pompeiiClient.println();

    pompeiiClient.println(postData);
    pompeiiClient.println();

    pompeiiClient.stop();
    pompeiiClient.flush();
    Serial.println("Called pompeii");
  }
}

int calculateWattsAndResetFlashes()
{
  if (impulseCount == 0UL) {
    return 0;
  }

  double watts = (impulseCount * multiplier) / (minutesBetweenCalls / minutesInHour);
  Serial.print("Calc'd Watts: ");
  Serial.println(watts);
  impulseCount = 0UL;
  return int(watts);
}

Combined with the inverted data upload from my server, I now have the ability to see the electricity import and generation at home from work 🙂

pvoutput import

And for my colleague, that’s real coding – not a single unit test in sight 😉 (joke)