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2010/08/13 Fine grained house-wide power monitoring with Brultech ECM1240, (with net metering support), and graphing with cacti
π 2010-08-13 00:00 in Computers, Linuxha, Solar


Until recently, I had a Brand One Powermeter to measure PG&E Meter, PV system and my AC. It was bulky, unreliable, and impossible to reprogram. In other words, it was a poor and expensive solution. That said, I still got some data and reasonable graphs from it as per this earlier blog post.

But let's be honest, I really didn't like that monitor and wanted to ditch it. After some research, the ECM1240 is the best feature/cost ratio power monitoring device I found (as of 2010). As of 2019, the ECM1240 is now obsolete and replaced by the Greeneye, see below:

_Note, there seems to be a better monitor now, the Greeneye._ You may want to have a look at Brultech Greeneye.

Why is it better than the alternatives?

  • you can monitor 7 (!) channels plus voltage for less than $200
  • you can use multiple devices to monitor more than 7 channels (I monitor 20 in my panel)
  • it comes with multiple CTs to chose from, from highly accurate high current split CTs or TTs to small quarter sized CTs that are appropriate for monitoring all your smaller loads behind each of your circuit breakers
  • you can monitor let's say 6 circuit breakers as one channel (like 'all lights').
  • the data gatherer can be connected to your computer via serial port (what I used), ethernet, or wireless (for comparison the TED device, aside from being a single channel device, can only communicate over your power lines, which is unreliable and almost a guaranteed disaster if you use X10 or insteon home automation).
  • the owner is helpful is responsive to intelligent questions
  • while the software is meant for windows, data can be gathered on linux or any OS that can run python (i.e. just about anything) thanks to provided in this page.
  • Here's what it looks like:

    the whole system
    the whole system

    I calibrated the TTs vs the split 60CTs and the small CT-40s by comparing measurements of the same load
    I calibrated the TTs vs the split 60CTs and the small CT-40s by comparing measurements of the same load

    the 2 white boxes are the ECMs1240s, but I also have my older and bigger brand one power meters in there
    the 2 white boxes are the ECMs1240s, but I also have my older and bigger brand one power meters in there

    the small donut CT-40s are great, they take no room at all
    the small donut CT-40s are great, they take no room at all

    After getting this installed, I was able to get data on linux after I got a working but incomplete (for me) from prior authors, Brian Jackson, Kelvin Kakugawa, and Amit Snyderman. I modified it to support net metering and show high precision data as required by proper per second graphing in cacti.


  • Here is a link to my improved
  • And is here my ecmread logfile to cacti/rrdtool converter.
  • My init script
  • My script to add labels to each channel
  • My generic page with logfile to cacti converters.
  • Gratuitous Graphs :)

    Ok, first you can find all the graphs here: all regular owfs derived graphs.
    And here are the interesting composite graphs.

    So, US houses come with 2 120V phases. Now, if you wanted 100% exact wattage measurements, you'd have to measure the voltage on each and every circuit breaker you measure, but in reality measuring each phase is close enough.
    In real life, measuring amps on one phase with voltage from another phase will only give you about a 1-2% error at worst, so it's not a lot to agonize about. In my setup I tried to measure phase 2 loads on my ECM that's plugged into phase 2 power, but wasn't fully able to do it, and it's not meaningful when you measure 240V loads anyway.

    This is what the phases look like, as the graph shows phase 1 typically gets more power than phase 2 for me, but depending on the load in my street and my house, they sometimes become close or equal:

    Of course, I have a lot of single interesting graphs. Can you tell when my disk to disk backup completed? :)

    More importantly, and worryingly, compiling the same kernel took 30mn and 20W on my dual core duo laptop:

    While compiling the same kernel on my dual Xeon P4 server took 2H and 80W-ish:

    Another interesting graph was charging a 12V marine battery for my UPS:

    Thanks to this graph, I was able to find that my TV and speakers took 30W when off. I got a smart power strip that turns them off totally and saved about 30W off my base load:

    Ever wonder how much power your fridge is really using?

    So, how much power does AC use? Well, not only 3500W for AC, but another 1000W for the whole house fans:

    A cool graph showing House Power Use (calculated) from PG&E meter and PV production probe:

    And for the money shot, all the house uses combined on one graph:

    And the same graph, but with AC that was activated:

    Setting up cacti

    See my cacti config page.

    Now, the tricky part is creating graph items that do not exist (like house use, or unmonitored house use). See this post I made on how to do this.

    The other tricky part is that I had my ECM graphs setup to refresh every 10 seconds, which is faster than the cacti poller which runs every minute. This post explains how I did a faster than 1mn refresh in cacti

    2010/08/06 Temperature, moisture, humidity, and UV monitoring and graphing with 1wire devices, owfs, and cacti
    π 2010-08-06 00:00 in Computers, Linuxha


    In a prior post, I wrote about using digitemp to talk to 1-wire temp sensors.
    Digitemp is a good first choice if you only care about temperature since it's already available in most linux distributions, and it's pretty easy to setup. However, digitemp is fairly limited: first it does not support anything but temperature, and one humidity sensor (with only one convertion table, and there are several depending on which one you end up buying). On top of that, the humidity sensor only works with the serial interface and not the USB one.

    1-wire supports a lot more than just temperature, including several kinds of humidity sensors, a moisture sensor which can be used to measure the amount of watering needed for your lawn, and outdoors UV and solar intensity sensors (available from hobby boards).
    1-wire also has weather stations, but you do have to worry about your pole with the wind sensor being hit by lightening that would then be channeled back inside your house and to your computer (not good). Also, I have not found 1-wire weather stations to be price competitive with an Oregon Scientific WMR968 which is wireless and can be directly connected and read from via its serial port on linux and through misterhouse.

  • wind: $140 (95+45) (or some more expensive $225)
  • baro: $60
  • humidity/solar x2 (indoors/outdoors): $120
  • rain gauge: $93
  • then add wiring and a possible hub ($50)
  • This gives you a total of $493. For comparison an oregon scientific WMR968 weather station costs $200 (see this thread for details on that) and my WMR 968/rfxcom page for my setup.

    After switching from digitemp, I realized that my single bus described here was really stretching the limits of a single bus. I therefore ended up adding a hub.

    What you need to know about the hub is that you get 6 buses split off your original bus (i.e. you get 7, one is the original bus passed through but with bus power added, and there are 3 1-wire switch chips with a MAIN and AUX sub bus each, effectively giving you 6 more busses). The Hobby-Boards 1-wire hub, which is the one I bought, injects regulated 5V power and unregulated 12-24V power for some special outdoors 1-wire devices on all the ports, including the pass-through one.
    Having a powered bus with 5 and 12-24V allows the use of some special 1-wire devices like the moisture meter, and the UV sensor.
    If you go with the hobby-boards hub, you should plan to wire like they do to make your life easier: hobby boards wiring chart.

    1-wire basic setup

    I talked about what to buy, and how to wire on my last Temperature monitoring and graphing with 1wire devices, digitemp, misterhouse, and cacti post. Go read that section.

    1-wire and star technology

    If you have a wiring closet where all your cables come back, you have a star topology. With a hub, you can have up to 7 branches, which may be enough for you. If however you need more than that, when you use the wiring chart from hobby-boards, I recommend that you use pair 3-6 as a return for pair 4-5: i.e. you send signal down your cat-5 to some location and then you connect 4 to 3 and 5 to 6 at the end point. You then connect 3 and 6 to 4 and 5 of your next Cat-5 run elsewhere in your house.
    When combining this techique and the 7 branches you get from a hub, this should give you more than plenty branches from your network closet.

    Hobby Boards 1-wire UV meter

    I added the Hobby-Boards UV sensor to my roof 1-wire bus now that it had bus power added to it after I got the hub, and I used cella-wrap to make sure water wouldn't get in the box or touch the 1-wire device wires and create a temporary bus short. The UV board also has a built in temp sensor, but the weatherproof box it comes with will act as a greenhouse somewhat, so the temperature read by that sensor will be higher than normal (it is used for UV readout temp correction). If you don't care about UV index as much and would like outside humidity level, you may want to consider the humidity/temp/solar sensor instead (I get outside humidity through my WMR968 Oregon Scientific Weather Station, so I didn't care to have that in my outside 1-wire sensor).

    UV sensor in mostly water proof box
    UV sensor in mostly water proof box

    gets inside the attic through a water proof hole
    gets inside the attic through a water proof hole

    Hobby Boards 1-wire Moisture Meter

    The moisture meter has a temp sensor on the moisture meter control board, but it is unfortunately not used to correct the moisture readings from the moisture probe (this sensor does have a moisture value that can vary up to 50% when fully wet between temperature extremes). Thankfully in real life, your soil temperature deeper down should not change too much and affect the reading too much.
    I then buried the control board too so that it could be used as a soil temperature sensor.

    moisture meter
    moisture meter

    the trick was not to bury the sensor too deep: just as deep as my grass roots
    the trick was not to bury the sensor too deep: just as deep as my grass roots

    protecting the board from water
    protecting the board from water

    regular DS18B20 outside temperature probe in the shade
    regular DS18B20 outside temperature probe in the shade

    The temperature graph is not super exciting, but still good info. It's reassuring that the dirt temp doesn't change much and therefore the moisture readings won't be foiled much:

    The moisture readings are more useful and for instance this graph shows how I wasn't watering enough, and turned up the sprinkler times a little bit so that the humidity ends up at a reasonable state:

    But the really interesting graph is seeing soil humidity over soil temperature (green) and outside temperature (red):

    what this graph shows is outside temperature obviously affecting soil temperature a little bit, and when soil temperature goes up on a wet sensor, it brings up the moisture reading somewhat unfortunately.
    Similarly, from the 1-wire side, you don't see a humidity percentage, but a negative current value

    cat /etc/owfs/moisture/35\ Front_Lawn/current; echo -1.35875

    I looked at the range of values I typically get for full dry and full wet, and this is definitely sensor and board dependent. There is also the problem that the hobby-board design up to 2010/05, did not have a ground loop isolation transformer (without which the sensor would behave erratically as soon as you put it in the ground). Once you add the isolation tranformer, it does change the current values for dry and wet though, so each person may have to compute their own. Unfortunately I've seen my sensor briefly return values all the way to -2.55 instead of the typical wet -1.74
    See the owfs moisture sensor page I wrote for details on this.

    This is the code I use for now:

    # 0.56625/0.5675 bone dry, but once got 0.335625.
    # glass of water yielded 1.74 but I've sometimes seen 2.555. What to use?
    my ($min, $max) = (0.33, 2.6);

    # value should be temp ajusted in an ideal world, but I don't have correction tables. $value *= -1; $value = $min if ($value < $min); $value = $max if ($value > $max); $value = (100 * ($value - $min) / ($max - $min));

    I've struggled on finding the upper value. First, I got -1.74 but eventually I sometimes got -2.55 out of the blue for a few samples, which yielded some clipping, so I changed the max value from -1.74 to -2.6 at noon on this graph, explaining the sudden dip. You can however you can see on the left the jump to 100% when the sprinklers were started:

    Despite the sensor being noisy, temperature dependent, and hard to calibrate, the overall graph is still useful enough to show whether your sprinklers are keeping the dirt moist enough, or if your overall moist is just going down (bad).

    Owfs setup

    But back to 1-wire and owfs, owfs is more work to setup but it's just the way to go if you want anything more than temperature monitoring.
    You need to start by getting the latest source code from, and compiling it. /configure --enable-debian did the right thing for me, but you need to make sure you have the right headers on your system

    I wrote this script, read_owfs that reads from an owfs symlink tree and generates a digitemp looking logfile so that it's easy to parse the logfile later with the same code regardless of whether you use digitemp or owfs to capture the data.

    owfs with a hub is a bit "interesting" since you have to find your devices in subtrees, which is why I made a symlink tree to make my life easier. I setup a symlink for each hub port and a chain name to point to each of the 3 buses' AUX or MAIN branch. This is what it looks like:

    /etc/owfs/bus1 -> /owfs/1F.F05005000000
    /etc/owfs/bus2 -> /owfs/1F.E25005000000
    /etc/owfs/bus3 -> /owfs/1F.E15005000000
    /etc/owfs/chain1 -> bus2/main
    /etc/owfs/crawlspace_chain -> bus2/aux
    /etc/owfs/dining_chain -> bus3/main
    /etc/owfs/roof_chain -> bus1/aux

    /etc/owfs/humidity/56 Hall_Closet -> ../chain1/26.2E4DF5000000/HIH4000 /etc/owfs/moisture/35 Front_Lawn -> ../crawlspace_chain/30.131A62120000

    /etc/owfs/temperature/11 Family_Room -> ../chain1/10.A8D1ED010800 /etc/owfs/temperature/12 Living_Room -> ../chain1/10.52D1ED010800 /etc/owfs/temperature/15 Garage -> ../chain1/10.2223EF010800 /etc/owfs/temperature/21 Attic -> ../roof_chain/10.5DE1ED010800 /etc/owfs/temperature/22 Roof -> ../roof_chain/10.94A2ED010800 /etc/owfs/temperature/23 Outdoors_Roof -> ../roof_chain/28.57B659020000 /etc/owfs/temperature/25 Roof_UV -> ../roof_chain/EE.E749CB010800 /etc/owfs/temperature/31 Crawlspace -> ../crawlspace_chain/10.F9F3EE010800 /etc/owfs/temperature/32 Outdoors_Crawlspace -> ../crawlspace_chain/10.D1D0ED010800 /etc/owfs/temperature/35 Front_Lawn -> ../crawlspace_chain/30.131A62120000 (...)

    This is how I start owfs and the xpl-owfs gateway:

    gargamel:/etc/owfs# cat /etc/init.d/owfs 
    case "$1" in
            umount /owfs 2>/dev/null
    	# serial
            /opt/owfs/bin/owserver -d /dev/DS9097U -F --error_print 0 --error_level 1 --nozero
    	# usb
            #/opt/owfs/bin/owserver -u -F --error_print 0 --error_level 1 --nozero
            /opt/owfs/bin/owfs    -F -s localhost:4304 /owfs --nozero
            /opt/owfs/bin/owhttpd -F -s localhost:4304 -p 8082 --nozero
    	# this comes from xpl-perl, reads /owfs devices and relays their data periodically
    	# over XPL, where they can be relayed to misterhouse.
            xpl-owfs --interface eth1 --owfs-mount /owfs >/dev/null &
            pkill -f '/opt/owfs/bin/owfs'
            pkill -f '/opt/owfs/bin/owserver'
            pkill -f '/opt/owfs/bin/owhttp'
            pkill -f 'xpl-owfs'
            $0 stop
            $0 start
            echo "Usage: owfs {start|stop|restart|force-reload}" >&2
            exit 1
    exit 0

    Gatewaying 1-wire data to misterhouse

    owfs-xpl is a good way to relay 1-wire data to misterhouse via its XPL gateway as opposed to reading owfs directly since you're assured not to hang.
    This is how you setup devices in misterhouse:

    XPL_SENSOR, bnz-owfs.*:10.2223EF010800, garage_temp, , temp
    XPL_SENSOR, bnz-owfs.*:28.3359C7010000, freezer_temp, , temp
    XPL_SENSOR, bnz-owfs.*:28.998D4D020000, computer_closet_temp, , temp
    XPL_SENSOR, bnz-owfs.*:26.2E4DF5000000, hall_closet_temp, , temp
    XPL_SENSOR, bnz-owfs.*:26.2E4DF5000000.1, hall_closet_humidity, , humidity

    If you use xpl-owfs, adding .1 behind a humidity value lets it pick another DA converter between the default one in owfs: .1 for HIH4000, and .2 for HTM1735 (it makes a difference since the analog value is turned into a different moisture percentage value as a result).
    Here's what it looks like and the patch for xpl-owfs if you are not running a recent one with that support:

    gargamel:~# grep . /owfs/26.2E4DF5000000/{.,*}/humidity
    /owfs/26.2E4DF5000000/./humidity:     58.8895
    /owfs/26.2E4DF5000000/HIH4000/humidity:     60.5681
    /owfs/26.2E4DF5000000/HTM1735/humidity:     56.8768

    --- /usr/share/perl5/xPL/Dock/ 2010-04-17 09:08:43.000000000 -0700 +++ /usr/share/perl5/xPL/Dock/ 2010-04-17 09:25:25.000000000 -0700 @@ -154,6 +154,8 @@ foreach my $dev (@$devices) { foreach my $rec ([ "temperature", "temp" ], [ 'humidity', 'humidity' ], + [ 'HIH4000/humidity', 'humidity', 1 ], + [ 'HTM1735/humidity', 'humidity', 2 ], [ 'counters.A', 'count', 0 ], [ 'counters.B', 'count', 1 ], [ 'current', 'current' ]) {

    Once you have misterhouse configured to receive XPL messages, with those in mh.private.ini:

    ipaddress_xpl_broadcast =
    ipaddress_xpl =
    # this is how you turn it off
    #xpl_disable = 1
    # if you are using a better XPL hub, turn off the mh built in one
    #xpl_nohub = 1

    Then, you can simply read owfs values in misterhouse via XPL like so:

    my $compcloset_temp = $computer_closet_temp->state()
    (there is one caveat there: misterhouse does not currently have a timer to remove the temperature value if you aren't getting updates from xpl/owfs)

    Note that there are other ways to read owfs in misterhouse, namely:

  • via xAP (just like xPL, but unless you're already using xAP for something else, don't bother with it)
  • iButton code in MH if you use the iButton 1-wire interface as opposed to a DS9097U (serial) or DS2490 (USB)
  • Owfs_item code in MH from Jim Duda. This one talks to owfs via its owfs_server daemon and perl bindings, but I've found this to be had to get to work because the owfs perl bindings haven't been reliable for me. Jim actually recommends using xPL for new installs, but if you want to try his code look at thread #1 (you need to open the messages after this one) and thread #2.
  • The summary of the threads I posted however is that xPL and xpl-owfs are the way to go for reading owfs sensors in mh.

    Feeding data in cacti / code

    Now that you have data available in /etc/owfs/*, and being sent to misterhouse via xPL, you can (and should) log it to a file.

    I have written two scripts for this:

  • read_owfs reads owfs data from a symlink tree in /etc/owfs/ and populates a digitemp looking file in /var/log/temperatures.
  • cacti_owfs reads a digitemp or owfs derived /var/log/temperatures file and converts it into rrdtool data or cacti compatible query data.
  • The second script is the important one which can generate cacti data or help you regenerate/build an rrdtool RRA file from scratch if you add fields or change your data format (my recommendation is to plan ahead and add extra fields in your RRD file for probes you might add later (you can't add fields after the fact without regenerating the entire file and refilling it with all the data from time 0, so it's better to plan ahead and get it right the first time, and a good way to do that is to just add extra fields that you're not using yet but can use later) ).

    For more details on cacti integration, see my Gatewaying 1-wire, XPL (Oregon Scientify Weather), Brultech ECM1240 Power Data, and Brand OneMeter Data to cacti page.

    cacti_owfs can also be used for feeding data in an rrdtool after the fact (--dump-cacti) and used like so:

    sort -u < dump | time xargs rrdtool update $RRD --template `cacti_owfs --cacti-dump-header`
    (after having freshly re-created the RRD and make sure you use --start 1271572300 with the right second value that's just before the first one in your dump).

    Setting up cacti

    See my cacti config page.

    Gratuitous Graphs :)

    Ok, first you can find all the graphs here: all regular owfs derived graphs.

    And here are the interesting composite graphs.

    I keep track of the humidity in our wine closet. This chart shows when I refilled the evaporation water plate:

    AC run on a warm day:

    I was curious to know if our old fridge in the garage was having unreasonable and too frequent on/off cycles. The old garage fridge does run a bit warmer but doesn't cycle that much more often than the new one, so I'm not as worried about it dying soon as much (it does take a fair amount of extra power though, being 10 years older):

    Interestingly enough, it is actually the newer kitchen freezer which has occasional big temp jumps to >50F.

    And this lets me keep track of temperature and humidity in our wine closet (the good news is the water plate in the closet does keep humidity higher compared to the house humidity level):

    2010/08/06 Booster Fans and Heating/Cooling with Outside Air with Misterhouse
    π 2010-08-06 00:00 in Computers, Linuxha


    So, my plan was to be able to use outside air to cool the house at night during the summer without leaving doors and windows open on one hand, while being able to boost or shutoff air to the master bedroom depending on the time and boost HVAC air to the family room which gets the warmest but is also the hardest to cool since it's at the end of the line.

    Boosting air is simply done by adding booster fans to the right ducts, but controlling the fans at the right time is where it gets interesting: I wanted to be able to decide not to turn on the booster fan to the bedroom during the day (waste of air) and not bother with trying to heat/cool the family room at night either since the master bedroom needs the air more than the family room.
    The astute reader will note that this is usually done with dampers, but the furnace we have is older and would require a pressure return for extra air if only one room were targetted, and dampers just add more money and complexity when I already wanted booster fans. The trick is that booster fans can act as semi dampers when they're not running, which is good enough.

    Now, the main goal was however to be able to pull air from the outside and bring it in the house. This was accomplished with the same 2 booster fans to create suction this time and 2 dampers do redirect the air from the furnace output to ducts that go outside the house.

    that was a few parts :)
    that was a few parts :)

    damper closed
    damper closed

    damper opened (notice the 2 small wires which got to my 1-wire 8 channel IO board)
    damper opened (notice the 2 small wires which got to my 1-wire 8 channel IO board)

    So, to cool down the house (or bring warm day air in during the day in the winter), I need to:

  • close the air coming from the furnace with a damper
  • open the air coming from outside with another damper (both happen at the same time)
  • turn on one or two of the booster fans to suck air from outside
  • make sure that at no time my HVAC system actually decides to turn on too, and if it does reset the dampers to allow air from the furnace (which is also the AC).
  • automatically do the above when there is a suitable temperature difference between inside and outside.
  • For normal operation, I have 2 HAI RC-80 and RC-90 thermostats, one for the house and one for the master bedroom. Depending on which one triggers, the booster fan to the appropriate zone should activate too.

    Do you have a zone board that can do all this?
    If so, how many hundred dollars is it and do you need to call an HVAC person with proprietary software to reprogram it?
    Do the inside and outside temperature probes cost $3 each, or more? :)

    If you want to skip ahead, this is the misterhouse hvac code I was able to write to control the hvac system.

    Implementation with Misterhouse

    This is where misterhouse comes in again, I can program absolutely any logic I want and mostly with sensors and actuators that cost a lot less than typical overpriced HVAC parts.
    The bits that came in play were:

  • HAI RC-80 thermostat which I can query for status (cooling/heating/HVAC fan on or off?) from misterhouse thanks to the code I wrote earlier (see my misterhouse HAI code). Actually I also use that code to know the temperature in the bedroom (which I could also get with a 1-wire sensor).
  • 1-wire temp sensors inside and outside the house. This is obviously useful to know whether air outside is the right temperature for bringing in, or not (see the Temperature, moisture, humidity, and UV monitoring and graphing with 1wire devices, owfs, and cacti for details on the owfs setup.
  • 1-wire 8 Channel I/O board which I use to control 24VAC to the dampers. One is normally closed and the other one normally opened. They each only need about 250mA to be held in the other position, so a single 500mA 24VAC power supply going through a relay on the 8 Channel I/O board is good enough. See my owfs 8 channel I/O page
  • 2 X10 (or Insteon) remotely controlled plugs to turn the booster fans on or off.
  • Here's a picture of the 1-wire 8 Channel IO board

    I then added some 1-wire temp sensors inside the ducts to confirm the temperature of the air going through them, and that's it. All that was left was some code, which you can find below.

    When both duct fans are running, the power graph shows they use 300W:

    Here is a temperature graph of cooling with outside air without using the AC showing a 5 degree decrease for dining room/family room:

    and for comparison cooling with just the windows open, which I don't quite want to do anyway (compare the family and diving room temps which only go down by 2 and 1 degree).

    For yet another comparison, the following link is a test with only the family room duct fan running (and not the bedroom one): that was a 3 and 1 degree decrease for the dining room/family room. Not as impressive.

    Yes, booster fans do require some electricity to run (150W a piece or so), but for comparison, AC is 3000W just for the AC, to which you have to add 1000W for for furnace whole house fan and then the 150W for the booster fan:

    At least, as a bonus, we do now get more cold air to the family room with the booster fan when we do run the AC, so we reach our target temperature more quickly.

    Top/Hvac Damper Open to Close Video (click me)
    Top/Hvac Damper Open to Close Video (click me)


    Here is my misterhouse hvac script that controls the booster fans and outside air intake depending on inside, outside temperature and HAI thermostat status.

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