Whole House Energy Monitoring

mikegrb — Mon, 28 Feb 2011 00:18:20 +0000

I placed an order for a TED 5000 on February 10th. The TED 5000 is a whole house energy monitor — a kill-a-watt for the whole house. I’ve spent a lot of time reading about the products available in this space. I’ve looked at about 10 products for whole house energy monitoring and three jump to the top. The wattvision, PowerHouse Dynamics’s eMonitor, and the TED 5000.

The wattvision (~$250) most closely resembles the TED in terms of price and features. The wattvision uses an optical sensor that counts the rotation of the disk in the utility meter. This sensor is connected to the device, which is powered by an AC adapter and sends the data to wattvision’s servers via your home wifi network. This is the easiest to install, but would require running the sensor cable from the outside to inside. Additionally, all data is sent to wattvision’s servers. I’d also need to subscribe to wattvision’s $8.99/month service for the other features I want (like API access.)

The eMonitor (starting around $688 for 12 circuits) is something I just recently discovered. Really, this is my ideal solution: for $1,277, you get the necessary equipment for monitoring the power feed plus 44 individual breakers. This gives a much better view of where your power consumption is going. Per-circuit monitoring also enables nifty alerts — an SMS for power draw in the kids room after school starts on a week day, or if the compressor on the fridge is running longer than normal (time to clean the coils, etc.) I just can’t justify the expense at $1,277. The price is certainly reasonable for what you are getting, but there is no way the wife would approve the purchase :/

The Energy Detective (TED, ~$200) from Energy Inc provides full house consumption monitoring like the wattvision. Unlike the wattvision, the data is stored and served from a gateway device on your home network. Two current transformers go around the two lines for the incoming split phase feed. These are connected to a box, which is installed next-to-or-inside the breaker panel. The breaker panel is powered and communicates via a connection to a breaker on each phase. The gateway is installed elsewhere in the house and plugs into an outlet for power and communication with the current sensor, and via Ethernet to serve its precious data up.

So, February 10th I finally got approval from the wife to order the TED and purchased the TED 5000-G with overnight shipping. It arrived as expected on the 11th and I was eager to install it. A coworker (also interested in the TED,) came over for dinner and to help out with the installation. I was too excited to wait for his arrival and finished the install before he got there ;-).

It’s now February 27th and I still don’t have a working TED system. The gateway I was originally shipped has a defective Ethernet port. It’s already been to Energy Inc and back and is still defective. They finally agreed to ship me a replacement gateway on the 25th but sent it with 2nd day shipping, which has the same transit time as ground (just more expensive.) The new unit should arrive March 1st.

Optional TED Display

I’m quite eager to get things up and running, and anticipate no problems once I have a working gateway. The most common issue people run into is excessive noise or attenuation of the power line communications (PLC) signal between the sensor and gateway. The forums seem to be full of people with lots of grief around this issue. The gateway does contain a ZigBee transceiver but that is for communication with the optional wireless display. Some have questioned switching from PLC to ZigBee for the current data but a device inside the metal breaker box would have a hard time getting any sort of RF signal out, and PLC seems the most logical solution (even with it’s inherent issues.) Of course, this is easy for me to say since I don’t anticipate having any issue with PLC. I can see a clear ~3-4Vpk signal on the zero crossing of the A/C at the outlet I plan to install the gateway:

I have another blog post in the works documenting my seemingly unending issues with the other half of the TED solution: the support staff and engineers backing the product. To be fair, the support staff is 1:2 — the second guy I spoke to there was great, but I’m pretty sure their engineers shouldn’t be allowed to know customers even exist, let alone talk to them on the phone. But, this is a story for my next blog post.

Quick & Easy Temperature Logging with the Arduino

mikegrb — Mon, 03 Nov 2008 03:29:50 +0000

Basic Voltage Divider with a Thermistor:

Typical voltage divider, matched would have made better sense but the thermistor was a random one salvaged from consumer electronics so I didn’t know the value in advance.

Would work just fine like this with TP1 connected to an Arduino analog input and Vcc and GND connected. Energy savings for the win though, connected the top of the divider (Vcc) to a digital pin on the Arduino. Set the pin HIGH when you want to take a reading, LOW the rest of the time. Now the divider is not consuming power when a reading isn’t being taken.

Arduino Code

int pinDivEn = 4;
int pinDivRead = 1;
int pinLED = 13;

void setup() {
Serial.begin(9600);
pinMode(pinLED, OUTPUT);
pinMode(pinDivEn, OUTPUT);
Serial.println("READY");
}

void loop() {
if (Serial.available() > 0) {
digitalWrite(pinDivEn, HIGH);
digitalWrite(pinLED, HIGH);
delay(100);
while (Serial.available() > 0)
int serByte = Serial.read();
Serial.println(analogRead(pinDivRead));
digitalWrite(pinDivEn, LOW);
digitalWrite(pinLED, LOW);
}
}

pinDivEn is the divider enable pin (Vcc), pinDivRead is the analog input connected to TP1 in the divider, pinLED is is a digital pin with an LED that is lit while a reading is taken.

Once the Arduino boots it sends READY on the serial port at 9600 bps. It then waits for any data to be available on the serial port, when bytes are available, the voltage divider is enabled, the LED is lit, the bytes on the serial port are consumed, the value of TP1 is read and then written to the serial port, the divider enable pin is brought back low and the led is extinguished.

Perl Code

#!/usr/bin/perl

use strict;
use warnings;

use IO::Handle;
use Device::SerialPort;

my $dev = tie (*FH, 'Device::SerialPort', "/dev/tty.usbserial-A4001JwW")
|| die "Can't tie: $!";

$dev->baudrate(9600);
$dev->databits(8);
$dev->parity("none");
$dev->stopbits(1);

open (my $log, '>>', 'ohms.log') || die "can't open: $!";
$log->autoflush(1);

# wait for arduino to boot
while (1) {
my $val = ;
last if $val;
}

print FH "1\n";
while (1) {
my $val = fh>;
next unless $val;
chomp $val;

my $vR2 = $val / 1023 * 5;
my $vR1 = 5 - $vR2;
my $i = $vR1 / 1_000 * 1_000;
my $R2 = $vR2 / $i;

print $log time . ' ' . $R2 . "\n";
# printf("V_R2=%.2fV, i=%.2fmA R2=%.2fKΩ\n", $vR2, $i, $R2);

sleep 10;
print FH "1\n";
}

Opens the serial port, waits for something (the Arduino sending ‘READY’ but it pays no attention to what) on the serial port then every 10 seconds sends a 1\n to the Arduino prompting it to send a value. The result of analogRead is an integer from 0 – 1023 so this is converted to a voltage. The current through the divider is found allowing the resistance of the thermistor to be solved for. The resistance and time are written to a space separated log file. If the thermistor wasn’t unknown it would make more sense to solve for the actual temp using the Steinhart–Hart equation or similar and logging that rather than the resistance.

Sample log file entries

1224349429 10.1195652173913
1224349439 10.3666666666667
1224349449 10.3666666666667
1224349459 10.3666666666667
1224349469 10.4943820224719
1224349479 10.3666666666667
1224349489 10.2417582417582

A few lines in a text file gets us a graph from the log file by way of GnuPlot:

set term png transparent nocrop enhanced font "./arial.ttf" 9 size 800, 600
set xdata time
set timefmt "%s"
set format x "%m/%d %H:%M"
set xtics rotate by -45
set title "Thermistor Value"
set xlabel "Date/Time"
set ylabel "Resistance (kOhms)"
set grid
set output "ohms.png"
plot \
"ohms.log" using 1:2 title "10 sec interval readings" linecolor 2, \
"ohms.log" using 1:2 title "Bezier fit curve" smooth bezier linecolor 4 lw 2, \
10 title "77 F" lw 2 linecolor 1

hmmm.... » electronics

Whole House Energy Monitoring

Quick & Easy Temperature Logging with the Arduino