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Power monitor update

by Riscy on October 5th, 2012

Well after setting the original system up it only lasted 4 days before the battery went flat. It appears I shouldn’t leave the radio on all the time on the remote node otherwise it chews through the battery very quickly. So I searched through the JeeNode examples to look for low power options.

One of the issues with low power mode for the ATmega is that it doesn’t maintain time accuracy, and the JeeNode doesn’t have a RTC (I’m thinking of getting one). So the best thing I think I can do is to just turn the radio off when not used. The other option is to tone down update rate, I’ll probably look at that after I’ve collected more baseline data.

So after working with the RadioBlip code from the Jeelib examples I came up with this:

#include
#include
#include
#include “kWh.h”

#define SEND_MODE 1

volatile bool adcDone;

// for low-noise/-power ADC readouts, we’ll use ADC completion interrupts
ISR(ADC_vect) { adcDone = true; }

// this must be defined since we’re using the watchdog for low-power waiting
ISR(WDT_vect) { Sleepy::watchdogEvent(); }

static byte vccRead (byte count =4) {
set_sleep_mode(SLEEP_MODE_ADC);
ADMUX = bit(REFS0) | 14; // use VCC as AREF and internal bandgap as input
bitSet(ADCSRA, ADIE);
while (count– > 0) {
adcDone = false;
while (!adcDone)
sleep_mode();
}
bitClear(ADCSRA, ADIE);
// convert ADC readings to fit in one byte, i.e. 20 mV steps:
//  1.0V = 0, 1.8V = 40, 3.3V = 115, 5.0V = 200, 6.0V = 250
return (55U * 1024U) / (ADC + 1) – 50;
}

class Port;
Port inputPort(1);
static unsigned long last;
static unsigned long totalblinks;

void setup() {
Serial.begin(57600);
inputPort.mode2(INPUT); // Set AIO mode as input
inputPort.digiWrite2(1); // Activate pull-up resistor for AIO

//rf12_config();
rf12_config(); // Apparently this is necessary
rf12_easyInit(1); // Send value at most every 3 seconds
last = millis();
rf12_control(0xC040); // set low-battery level to 2.2V i.s.o. 3.1V
rf12_sleep(RF12_SLEEP);
}

void loop () {

static boolean ledOn = false; // Variable to indicate LED status
int data = inputPort.anaRead();
rf12_easyPoll();
if (!ledOn && data > 760) {        // After testing I found the switching point was 750
ledOn = true;
} else if (ledOn && data < 740) {
ledOn = false;
ledBlink();
totalblinks++;
}
}

void ledBlink() {
static int nBlinks = 0;
unsigned long time = millis();
unsigned long interval = time – last;

nBlinks++;
if (interval < 0) { // millis() overflow
last = time;
nBlinks = 0;
} else if (interval > 1000) { // 1+ sec passed
// Blinks are 1000 per kWh, or 1 Wh each
// One hour has 3.6M milliseconds
long watts = nBlinks * 1 * 3.6E6 / interval;

byte vcc = vccRead();
wattSend(watts,totalblinks,vcc);

last = time;
nBlinks = 0;
}
}

static void wattSend(long watts,long blinks, long vcc) {
Packet_t packet;
packet.lang = LANG_ELECTRICITY;
packet.mesg = MESG_ELEC_CURRENT;
packet.data = watts;
packet.blinks = blinks;
packet.vcc = vcc;
rf12_sleep(RF12_WAKEUP);
while (!rf12_canSend())
rf12_recvDone();
rf12_sendStart(0, &packet, sizeof packet);
rf12_sendWait(SEND_MODE);
delay(10);
rf12_sleep(RF12_SLEEP);
}

The code also contains parts which measures the Vcc voltage so I can determine when the battery pack is starting to get low.

The receiver code needed to change too. I wanted to include not just power, but the number of blinks and the new Vcc measurement. Here is the new code:

#include
#include
#include “kWh.h”

void setup() {
Serial.begin(57600);
//rf12_config();
rf12_config();
}

void loop() {
if (rf12_recvDone() && rf12_crc == 0 && rf12_len == sizeof (Packet_t)) {
Packet_t packet = *(Packet_t *) rf12_data;

if (packet.lang == LANG_ELECTRICITY) {
if (packet.mesg == MESG_ELEC_CURRENT) {
wattShow(packet.data,packet.blinks,packet.vcc);
}
}
}
else {
delay(10);
}
}

static void wattShow(long watts,long blinks,long vcc) {
Serial.print(watts);
Serial.print(“,”);
Serial.print(blinks);
Serial.print(“,”);
Serial.println(vcc);
}

I also changed the receiving Perl script to put the data into a MySQL database instead of dumping to a text file.

use strict;
use warnings;
use DBI;
use LWP::Simple;

use Win32::SerialPort qw( :STAT 0.19 );
use POSIX qw/strftime/;

my $port = Win32::SerialPort->new(‘COM9’);

my $time = time;

# MYSQL CONFIG VARIABLES
my $host = “192.168.1.101”;
my $database = “powermonitor”;
my $tablename = “data”;
my $user = “powermonitor”;
my $pw = [the password];

if( ! defined($port) ) {
die(“Can’t open COM9: $^E\n”);
}

my $outfd;
open ($outfd, “>>”, “log.txt”) or die “Failed to open output file – $!n”;

my $output = select(STDOUT);
$|++;
select($outfd);
$|++;
select $output;

$port->initialize();

$port->baudrate(57600);
$port->parity(‘none’);
$port->databits(8);
$port->stopbits(1);
$port->write_settings();
$port->are_match(“\n”);

while(1) {
my $char = $port->lookfor();
if ($char) {
$char =~ s/\xd//g;
if($char =~ m/(\d+),(\d+),(\d+)/){
my $dbh = DBI->connect(‘DBI:mysql:’.$database.’;host=’.$host, $user, $pw, { RaiseError => 1});
my $thedate=strftime(‘%Y-%m-%d %H:%M:%S’,localtime);
my $pvdate = strftime(‘%Y%m%d’,localtime);
my $pvtime = strftime(‘%H:%M’,localtime);
my $pvoutput = “get http://pvoutput.org/service/r2/addoutput.jsp?key=[the api number]&sid=[the sid number]&d=$pvdate&pt=$pvtime&ip=$1”;

#my $content = get $pvoutput;

my $sth=$dbh->prepare(“INSERT INTO $tablename VALUES(‘$thedate’,’$1′,’$2′,’$3′)”)
or die “Can’t prepare SQL statement: $DBI::errstr\n”;
$sth->execute
or die “Can’t execute SQL statement: $DBI::errstr\n”;
$dbh->disconnect();
}
sleep (1);
}
}
$port->close();
exit(0);

This is the database structure:

— Server version: 5.5.24

— Database: `powermonitor`

— Table structure for table `data`

CREATE TABLE IF NOT EXISTS `data` (
`date` datetime NOT NULL,
`watts` int(11) NOT NULL,
`blinks` int(11) NOT NULL,
`vcc` int(11) NOT NULL,
PRIMARY KEY (`date`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Now finally I wanted to graph the data but I haven’t found a good graph program for the front-end. So I’m using PVoutput, I’m not sure how it will work but I wrote this script to dump usage data for 5 minute intervals. It calculates averages and power usage data for the last 5 minute period, I initiate it using cron.

use strict;
use warnings;
use DBI;
use LWP::Simple;
use LWP::UserAgent;
use HTTP::Request::Common qw(POST);

use POSIX qw/strftime/;

# MYSQL CONFIG VARIABLES
my $host = “192.168.1.101”;
my $database = “powermonitor”;
my $tablename = “data”;
my $user = “powermonitor”;
my $pw = “powermonitor”;

my $thetime=int(time() / 300) * 300;
my $thetime_5=$thetime-300;
my $thetimestring=strftime(‘%Y-%m-%d %H:%M:%S’,localtime($thetime));
my $thetime_5string=strftime(‘%Y-%m-%d %H:%M:%S’,localtime($thetime_5));

my $dbh = DBI->connect(‘DBI:mysql:’.$database.’;host=’.$host, $user, $pw, { RaiseError => 1});

my $sth=$dbh->prepare(“select DATE_FORMAT(MIN(date), ‘%Y-%m-%d’) as day, max(blinks)-min(blinks) as Wh, round(avg(watts)) as Watts, Date_format(Min(date), ‘%H:%i’) as time from data where date > ‘$thetime_5string’ AND date < ‘$thetimestring’ GROUP BY ( 12 * HOUR( date ) + FLOOR( MINUTE( date ) / 5 ));”)
or die “Can’t prepare SQL statement: $DBI::errstr\n”;
$sth->execute
or die “Can’t execute SQL statement: $DBI::errstr\n”;
my @result = $sth->fetchrow_array();
my $pvdate= substr($result[0], 0, 4).substr($result[0],5,2).substr($result[0],8,2);
my $pvwatth= $result[1];
my $pvwatt= $result[2];
my $pvtime= $result[3];
print “$pvdate $pvwatth $pvwatt $pvtime\n”;
$sth->finish();
$dbh->disconnect();

my $url = “http://pvoutput.org/service/r2/addstatus.jsp”;

my $ua = LWP::UserAgent->new( timeout => 120 );
$ua->default_header(‘X-Pvoutput-Apikey’=> “edaf9593007119df34f393acbd36703b7476457b”);
$ua->default_header(‘X-Pvoutput-SystemId’=> “12265”);

my $req = POST $url, [
d => $pvdate,
t => $pvtime,
v3=> $pvwatth,
v4=> $pvwatt
];

my $content = $ua->request($req)->as_string;

print $content;

I’ll post a link to my PVOutput data once it looks ok.

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