Since getting my meter online, it has been sending its readings to a server in the sky so charts like these can be produced. To really play with the data, I needed to start logging it locally and producing my own graphs. Here is a rambling rundown of how I got from XML being spat out by the device every 6 seconds to something like this:
Step One – Parsing the data
This was the easy part; AndySC had already put together a perl script for reading the serial port and doing the necessary parsing.
Step Two – Publishing the data
Again, not much for me to do here as Andy’s script already publishes the data to a set of topics over MQTT.
Step Three – Logging the data
Finally, something for me to do. A couple years ago, I would have joined Andy’s perl script with one of my own, but python is more my thing these days. I already had a piece of python that subscribes to the appropriate topics and posts the temperature values to twitter. It didn’t take much to get the same script to subscribe to the power data and dump it into a MySQL database on the local machine.
+----------------+---------+ | when | power | +----------------+---------+ | 20080502231747 | 0.34 | | 20080502231753 | 0.33 | | 20080502231804 | 0.34 | +----------------+---------+
The table in the database is a very simple one at the moment; logging the power along with a timestamp. An entry is added to the table for every reading from the meter and having been running for 3 days there are just over 11,000 of them. I’ll have to keep an eye on this to make sure it doesn’t run away with my free disk space.
Step Four – Graphing the data
Roo showed me some stuff he’s been playing with using the Google Chart API. Whilst I generally prefer to roll my own (aka, reinvent the wheel), I couldn’t ignore just how easy it is to produce pretty graphs this way.
Before delving into the API, I needed to decide just what I wanted to produce. As there is such a range of chart types available, there are plenty of interesting things that could be done. Initially, however, I decided to stick with the traditional “power-usage-in-the-last-24-hours” chart.
The API has a limit on the amount of data that can be passed to it. So I needed to find a meaningful way to reduce the 4200 data points generated in 24 hours to around 100 at most. I soon settled on using the average value for each 10 minute period. This loses some resolution in the data, but it still shows the trends.
Generating the averages is a simple question of the right query on the database. With some trial and error, I eventually got to:
select concat(substring(substring(`when`,1,11),9,4),'0'), truncate(avg(`power`),3) from currentcost where `when` > SUBDATE(NOW(), INTERVAL 1 DAY) group by substring(`when`,1,11) order by `when`;
Simple huh?
This produces results like this:
+------+-------+ | 2240 | 0.714 | | 2250 | 0.637 | | 2300 | 0.406 | +------+-------+
With that in place, all it took was to throw it together into an appropriate URL for google to generate the image:
http://chart.apis.google.com/chart?chg=100,20,1,7&chxt=y,x&
chxl=0:|0|1|2|3|4|5| 1:|2100|2300|0100|0300|0500|0700|0900|1100|1300|1500|1700|1900& chxp=1,2,11,19,27,36,44,53,61,69,78,86,95&chs=400×200 &cht=lc&chds=0,5&chm=B,f3f3f3,0,0,0&chco=aaaaff& chd=t:0.348,0.348,0.319,0.311,1.285,0.683,0.338,0.349, 0.398,0.39,0.356,0.477,0.274,0.264,0.572,0.637,0.406, 0.382,0.368,0.324,0.325,0.917,0.322,0.358,0.342,0.318, 0.191,0.124,0.209,0.204,0.192,0.213,0.205,0.196,0.374, 1.753,1.537,0.976,0.552,0.556,0.513,0.433,0.363,0.341, 0.575,0.46,0.188,0.123,0.248,0.204,0.195,0.116,0.215, 0.207,0.226,1.574,0.636,0.214,0.206,0.209,0.204,0.648, 0.694,0.628,0.599,0.689,0.743,1.222,0.278,0.394,0.326, 0.394,0.225,0.184,0.13,0.145,0.23,0.226,0.222,0.133, 0.133,0.237,0.231,0.223,0.13,0.234,0.229,0.222,0.203, 0.197,0.193,0.17,0.198,0.176,0.275,0.328,0.287,0.212, 0.159,0.192,0.19,0.212,0.292,0.298,0.418,0.332,0.789,0.894,0.719
Again, simple huh? Well, maybe not so much. Here’s a break down of what that does (and just to confuse matters, this is in a different order to where things appear in the url above…)
http://chart.apis.google.com/chart?
This is base url of the Google Charts api – all the magic comes from here.
chs=400×200
Set the size of the image.
&cht=lc
Set the type of chart – a line chart.
&chg=100,20,1,7
Gives the chart a grid in the background.
&chxt=y,x
&chxl=0:|0|1|2|3|4|5| 1:|2100|2300|0100|0300|0500|0700|0900|1100|1300|1500|1700|1900
&chxp=1,2,11,19,27,36,44,53,61,69,78,86,95
Describes the axis labels. 0 to 5 on the y-axis, and the relevant times along the x-axis. The script figures out approximate positions along the axis for the labels.
&chds=0,5
Specifies the minimum and maximum values for the data – although I occasionally go over 5Kw, I decided it wasn’t worth squeezing the data for 99% of the time when it is below that.
&chm=B,f3f3f3,0,0,0
Fills the area under the line with a light gray.
&chco=aaaaff
Draws the line with a light blue.
&chd=t:0.348,0.348,0.319,0.311,1.285,0.683,0.338,0.349, 0.398,0.39,0.356,0.477,0.274,0.264,0.572,0.637,0.406, 0.382,0.368,0.324,0.325,0.917,0.322,0.358,0.342,0.318, 0.191,0.124,0.209,0.204,0.192,0.213,0.205,0.196,0.374, 1.753,1.537,0.976,0.552,0.556,0.513,0.433,0.363,0.341, 0.575,0.46,0.188,0.123,0.248,0.204,0.195,0.116,0.215, 0.207,0.226,1.574,0.636,0.214,0.206,0.209,0.204,0.648, 0.694,0.628,0.599,0.689,0.743,1.222,0.278,0.394,0.326, 0.394,0.225,0.184,0.13,0.145,0.23,0.226,0.222,0.133, 0.133,0.237,0.231,0.223,0.13,0.234,0.229,0.222,0.203, 0.197,0.193,0.17,0.198,0.176,0.275,0.328,0.287,0.212, 0.159,0.192,0.19,0.212,0.292,0.298,0.418,0.332,0.789,0.894,0.719
Specifies the data points.
What next?
- Chris has started doing some interesting data analysis to see if he can automatically spot ‘events’ on the graph. Will be interesting to see what can be achieved here.
- Andy’s twittering house got some linkage last week from both Earth2Tech and Wired Science. They mention the power orb that was written about last year. I really like the idea of an ambient device for displaying this information – another project for the arduino list.
1
Chris Hodgins, 11:44 pm, May 5, 2008
Really nice solution! I also ran into the URL API limit but as you so neatly show you can still get some really nice results using data averaged over 10 minutes.
My data analysis is still pretty basic and works well for items with distinct characteristics. More thinking is required to separate the indistinct items as well.
Great job!
Chris
2
Steve Crossan, 8:54 am, May 6, 2008
Nice piece. As an FYI the restriction on calls to the Google Chart API has now been lifted. I like your solution for reducing the data points though.
Steve
3
pingback from Breakdown of currentcost xml output « Cumbers, 8:31 am, May 7, 2008
[...] Thomas, Chris Hodgins, Nick O’Leary and of course Andy-SC, and with Nick’s excellent guide to getting the data and creating custom graphs, I thought it would be good to blog about the actual xml data, and in doing so create a reference [...]
4
Andrew Carr, 7:41 pm, May 12, 2008
Hi,
I’ve been following your blog post (and Roo’s) about using the CurrentCost meter, and I’ve managed to stag one from the eco gadget shop.
I’d really like to do some fancy graphing with the Google Charts API; is it really cheeky to ask for you to provide me the perl script that AndySC put together to pull the data off the unit?
Cheers,
Andy
5
trackback from Roo Reynolds - What's Next?, 8:20 am, May 13, 2008
Current Cost Charting fun…
Nick has already written a nice introduction to using the Google Chart API for drawing charts of household power consumption over time. I’ve been playing with some other parts of the API as part of setting up a web-based dashboard so Rachel and…
6
nick, 11:00 pm, May 13, 2008
Hi Andy,
I’m not able to share the exact perl script I use as it does contain some proprietary code that enables us to share the data we’re producing. I can however give you some simple pointers for rolling your own.
The basic code is as follows:
The value for
$serial_portwill depend on your setup. This code assumes you are on a linux box, and are connected via USB. If you are connecting over serial directly, it is more likely to be something like/dev/ttyS0.I hope this helps you get started with charting your data.
7
pingback from dale lane » Blog Archive » CurrentCost - first impressions, 1:06 pm, May 15, 2008
[...] the data into graphs and charts: Nick, [...]
8
Chris, 5:38 pm, May 17, 2008
Just got a currentcost box, wiring it up now. Has anyone documented the pinout of the RJ45 connection?
Also any idea whether it uses CTS/RTS or maybe some other flow control like XON/XOFF…?
thanks
9
Chris, 11:31 pm, May 17, 2008
OK, I managed to connect it to my mac with Roo’s help: http://flickr.com/photos/pixelfrenzy/2499443217/
10
nick, 11:35 pm, May 17, 2008
Hi Chris, glad to hear you managed to get it connected. Look forward to seeing what you do with it next.
11
pingback from plus six » Counting the Cost, 1:02 am, May 18, 2008
[...] couple of weeks ago I came across a bunch of blogs written by IBM folk at Hursley Park, in which they described how they’d been playing with the [...]
12
pingback from CurrentCost « log.illsley.org, 1:17 pm, May 26, 2008
[...] are lots of interesting things to do with the data, which I’ll start to play with once I have a [...]
13
Dale Lane, 3:07 pm, May 27, 2008
RE: I’ll have to keep an eye on this to make sure it doesn’t run away with my free disk space.
I’m using a similar MySQL DB structure to you (naturally, since I nicked your scripts to get me started
), and have been checking the size it takes.
On my NSLU-2, each update requires 9 bytes.
A few rough back-of-the-envelope calculations:
Assume we store an update every 6 seconds – each needing 9 bytes of storage.
1 day == 24 hours
== 24 * 60 minutes
== 24 * 60 * 60 seconds
== (24 * 60 * 60) / 6 updates
So that is 14400 updates in a day – requiring 129600 bytes of storage
Multiply that by 365, and we need approx. 45 MB (47304000 bytes) for a full year’s data.
Think it’ll be a while before this starts being a problem
14
pingback from dale lane » Blog Archive » Accessing MySQL from Perl on SlugOS, 3:52 pm, May 27, 2008
[...] I decided to make a start on collecting the data. My plan was to copy what Nick had done and create a MySQL database to store the info, with a table to store a timestamp and the watt [...]
15
abu21, 11:28 am, June 4, 2008
hey,
Chk this out visifire, i think it can improve the quality of your charts coz it is powered by silverlight
16
nick, 2:10 pm, June 4, 2008
abu21, thanks for the comment.
I would question how a completely proprietary technology that only works on Windows would improve the quality of these graphs.
17
abu21, 7:56 am, June 5, 2008
hey nick,
visifire is under GPL, what else can one ask for.
regarding silverlight, microsoft is dieing to make it reach every one. currently silverlight supports win & mac. linux will follow soon ( some thing called moonlight)
18
nick, 8:33 am, June 5, 2008
@abu21,
True, Moonlight is being worked on by the guys at Novell. Once they get something released that I can easily install, then I may take a look.
Certainly the fact they plan for a proper SDK on linux will be an advantage over Flash.
In the mean time, I’ll stick to my open standards.
19
andyp, 9:15 am, June 5, 2008
I have to say that the fact that Google Charts are basically just spitting out PNGs for display makes them far more flexible across a range of devices anyway. Opera Mini on my BlackBerry can cope with that, for instance
20
pingback from Effing the Ineffable » Interfacing the CurrentCost meter to your PC, 5:54 pm, June 15, 2008
[...] a simple little gadget that measures power usage in your house. These are being discussed on IBM blogs everywhere, because while the device itself is very neat, it also has the ability to output the [...]
21
pingback from dale lane » Blog Archive » CurrentCost - getting the history into Windows, 10:33 pm, June 15, 2008
[...] plan The more geeky amongst us have connected the CurrentCost to a server of some sort. By connecting it to something [...]
22
trackback from Graham White: My Notes, 4:31 pm, July 29, 2008
Graphing Current Cost…
After hooking up my Current Cost Meter to a database recently I’ve been logging my power usage so the next step is to look at what I can do with the data. As I mentioned when I introduced my meter lo……
23
Christy Simmons, 2:36 pm, August 1, 2008
Any way we can submit or suggest a great graphing tool to you? Please email me for more info..i have something that you might want to blog about!
24
nick, 3:14 pm, August 1, 2008
@Christy – if you have something to suggest, feel free to post details here. Or you can send me the details directly to nol @ this site.
25
dollarone, 4:07 pm, September 6, 2008
Andrew Carr and others who have looked for a script to read the Current Cost data:
#!/usr/bin/perl
# Based on logger.pl by Bruce S. Garlock 2002-09-11
# (see http://aplawrence.com/Unix/logger.html)
# Requirements: Device::SerialPort 0.12 (from cpan)
use Device::SerialPort 0.12;
$LOGDIR = “~/log”; # path to data file
$LOGFILE = “currentcost.log”; # file name to output to
$PORT = “/dev/ttyS0″; # port to watch
# Serial Settings
$ob = Device::SerialPort->new ($PORT) || die “Can’t Open $PORT: $!”;
$ob->baudrate(2400) || die “failed setting baudrate”; # set to 9600 if you have the newer version
$ob->parity(”none”) || die “failed setting parity”;
$ob->databits(8) || die “failed setting databits”;
$ob->handshake(”none”) || die “failed setting handshake”;
$ob->write_settings || die “no settings”;
# open the logfile, and Port
open(LOG,”>>${LOGDIR}/${LOGFILE}”) || die “can’t open smdr file $LOGDIR/$LOGFILE for append: $SUB $!\n”;
open(DEV, “<$PORT”) || die “Cannot open $PORT: $_”;
select(LOG), $| = 1; # set nonbufferd mode
# Loop forver, logging data to the log file
while($_ = ){ # print input device to file
print LOG $_;
print STDOUT $_; # optional logging to STDOUT
}
undef $ob;
26
pingback from knolleary » Blog Archive » CurrentCostuino, 11:16 pm, November 19, 2008
[...] have previously mentioned that part of the setup used to graph the power data online was to publish the data to a [...]
27
pingback from dale lane » Blog Archive » HomeCamp, 7:27 pm, November 30, 2008
[...] leave a low-powered server connected to the meter constantly, collecting every update and maintain your own history (e.g. with a Slug or Viglen-MPC, storing every update from the meter in MySQL) [...]