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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 9th 2011 edited
     
    Finally got around to getting up there and retrieving the data. Have changed the sampling rate to every hour and so have also changed the charting, now as three charts, Loft, Roof and Ambient so that they are not too cluttered.
    Temperature data is on the left y-axis, Relative Humidity is on the Right y-axis.
    Temperature data should be the Red line, Humidity the Green Line and the Dew Point Temperature the Blue line.
    Watch out for scale changes on the y-axis.
    Still not had any condensation and there has now been a night below zero and some misty days.
      Loft 30-10-2011.jpg
      Roof 30-10-2011.jpg
      Ambient 30-10-2011.jpg
    • CommentAuthorwookey
    • CommentTimeNov 11th 2011 edited
     
    Damon OWFS works fine on ARM - it's what's been running my solar system for the last 3 years. Annoyingly it hasn't been officially packaged until very recently (in Debian, it's still not in Ubuntu). However I put up some packages for maverick natty and squeeze (amd64, i386 and arm) here: http://wookware.org/software/repo/

    The official (and more recent) Debian packages are in wheezy: http://packages.debian.org/wheezy/owfs

    ibuttons are indeed nifty, but you have to fish them out to read them. If you want to wire sensors up permanently then there are wired versions of the same sensors. This is what I have quite a few of: http://wookware.org/pics/solar/062-img_2777.jpg.html (that's two sensors attached to one board). They tend to cost about £3 each, but I bought 100 from poland for 90p each on ebay last year. You can also buy nice encapsulated ones from china with a molex connector on about 1m of cable for a fiver - with 3 wires unlike all the annoying people who supply 2-wire versions.
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 12th 2011 edited
     
    Posted By: wookeyibuttons are indeed nifty, but you have to fish them out to read them


    Yes this is the biggest problem with the standard ones, you can get a holder and extension lead though. Or just DIY it on a bit of CAT5/TELCO wire.
    Just wish there was a similar one that did W/m^2, that would be really useful.
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 12th 2011
     
    My home made temp logger uses those DS18B20 sensors. Dead easy to use, as pretty much any cheap little microcontroller can interface to them easily with only a simple little bit of code needed. It's nice that they come pre-calibrated and chuck out data in deg C, too, makes handling the data stream much easier. My little logger just uses a simple PIC with three sensors at the moment, plus a real time clock and a bit of EEPROM to hold the data. The logger can just dump the data as a CSV file to a PC via a port whenever needed, but has enough memory to log for well over two weeks (at a 6 min sample period) without needing to be downloaded. At the moment I'm only logging the outside and inside temperature plus my heating system flow temperature, as I'm trying to get a feel for the system response characteristics. The plan is to expand the number of sensors and look at similar things to ST, like humdity and dew point up in the loft where I've had condensation problems in the past (hopefully now fixed).
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 12th 2011
     
    wookey: thanks indeed for that, I think you've basically just done everything that ST was hoping me to work out!

    So, do you think that can I find a .deb for armv5tel and manage to run it on my existing Ubuntu 9.04 / 2.6.31 kernel without too much messing about?

    (BTW, like the wired sensors, but do I have to have them supplied with their own section of floorboard glued on like that? B^> )

    For the next round, or the one after, as ST has just done, I'll probably put back the sampling rate so I only have to fish them out once a quarter to avoid losing data.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 12th 2011 edited
     
    Posted By: DamonHDSo, do you think that can I find a .deb for armv5tel and manage to run it on my existing Ubuntu 9.04 / 2.6.31 kernel without too much messing about?

    What are you two talking about :bigsmile: 5 armed monkeys with nuts, whatever next!
    I am only trying to save buying a copy of Windows so I can use the CC as a logger on a very low power PC.
    Though have found out that closing the lid on the laptop saves between 5 and 7 Watts.

    We should be able to calculate a decent sampling rate from existing data. Just that the SE goes up.
    • CommentAuthorborpin
    • CommentTimeNov 12th 2011
     
    As far as I can see, the problem is the DS18B20 sensors only do temperature and do not do Humidity. Is there a similar bare sensor for humidity or just the iButtons? I could hook the sensors together but I would use one of the preconfigured ethernet loggers from embeddeddatasystems.com.
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 12th 2011
     
    I don't really want to run a permanent connection since that implies permanent power drain, unless the system has been designed to avoid it, and my whole server only uses about 4W (and every live Ethernet connection implies about another 1W).

    I'm not looking ST's gift-horse in the mouth: these iButton jobbies are great!

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 12th 2011
     
    Posted By: borpinAs far as I can see, the problem is the DS18B20 sensors only do temperature and do not do Humidity


    Something like this?
    http://www.datanab.com/sensors/1Wire_tempHumProbe.htm
    • CommentAuthorEd Davies
    • CommentTimeNov 12th 2011 edited
     
    There are lots of low power ARM based machines around but one cheap and low-hassle version is the Pogoplug. I got one from amazon.co.uk a couple of months ago:

    http://edavies.me.uk/2011/09/ssh-pogoplug/

    I've put Debian on it (it's Linux out of the box, of course, but some version for their file sharing application) and I'm just finishing off some node.js (http://nodejs.org/) code to log the performance of a Morningstar TriStar MPPT 60A controller with it (via its Modbus over TCP/IP interface). I'll need to have a look into 1-wire pretty soon.

    Power consumption when not too busy seems to be around 4 W plus whatever the disk needs.
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 12th 2011 edited
     
    I am already running the SheevaPlug which is the basis of the PogoPlug.

    http://www.earth.org.uk/note-on-SheevaPlug-setup.html

    http://www.theregister.co.uk/2010/11/11/diy_zero_energy_home_server/

    and I don't want to upend its configuration too much since I'm already running a host of servers on it and have tweaked it for power efficiency as-is.

    The other point is, adding an always-connected set of sensors would likely swamp the consumption of the server without great care, and make continuing to power it from my off-grid solar impractical, in winter when I most want the monitoring.

    Look at the bottom graph here and see what a run of cloudy weather is doing to my storage, even newly expanded to ~20 days' worth:

    http://www.earth.org.uk/off-grid-stats.html

    Rgds

    Damon
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 12th 2011
     
    Using full-blown processors, even cut down Linux ones, seems like going way, way OTT for just doing a bit of simple temperature and humidity logging around the house. My simple logger will potentially record data from dozens of sensors on a one-wire network and will run for a year or so on three AA duracells (not worth plugging it in to the mains, as the PSU losses would exceed the logger power consumption!). There are loads of these things around, using a wide range of different ucontroller chips. If you don't want the hassle of investing in programming kit then one of the many port programmable devices (like an Arduino or maybe even a Picaxe) would do the job very cheaply. You could arrange for one of these to periodically (maybe every month or so) dump data to a PC, but the PC only then needs to be on for the few seconds needed to do the data dump.
    • CommentAuthorborpin
    • CommentTimeNov 12th 2011
     
    Posted By: JSHarrisUsing full-blown processors, even cut down Linux ones, seems like going way, way OTT for just doing a bit of simple temperature and humidity logging around the house.
    But only if it is only doing that. If it is doing something else anyway (I run my own mailserver on a Acer Revo) then the additonal cost is minimal (and quite fun). Never really got inot embedded processors and certainly do not have the time now!
    • CommentAuthorborpin
    • CommentTimeNov 12th 2011 edited
     
    Posted By: SteamyTea
    Posted By: borpinAs far as I can see, the problem is the DS18B20 sensors only do temperature and do not do Humidity

    Something like this? http://www.datanab.com/sensors/1Wire_tempHumProbe.htm

    Sort of except it is 2 wire not 3 and seems is not readily available. More a bare sensor that can be wired up to a permanent 1-wire bus like Wookey has. Seems the DS1923 iButton is the only one and I am surprised that iButton don't seem to offer and 'permanent' wired solution. Best I can see is http://www.maxim-ic.com/datasheet/index.mvp/id/2976 else you need to make one yourself.
    • CommentAuthorborpin
    • CommentTimeNov 12th 2011
     
    Posted By: DamonHDI am already running the SheevaPlug which is the basis of the PogoPlug.

    Impressive! My current setup is so inefficient currently with routers off routers, so the new house design will address that. My one luxury is a NAS Duo. Not sure what it draws but it makes me feel more comfortable my data is secure.
    Recommendations for a meter to test power draw?
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 12th 2011
     
    <blockquote><cite>Posted By: borpin</cite><blockquote><cite>Posted By: SteamyTea</cite><blockquote><cite>Posted By: borpin</cite>As far as I can see, the problem is the DS18B20 sensors only do temperature and do not do Humidity</blockquote>
    Something like this? http://www.datanab.com/sensors/1Wire_tempHumProbe.htm</blockquote>
    Sort of except it is 2 wire not 3 and seems is not readily available. More a bare sensor that can be wired up to a permanent 1-wire bus like Wookey has. Seems the DS1923 iButton is the only one and I am surprised that iButton don't seem to offer and 'permanent' wired solution. Best I can see is http://www.maxim-ic.com/datasheet/index.mvp/id/2976 else you need to make one yourself.</blockquote>

    Sparkfun (one of my favourite places!) do a one wire temp/humidity module: http://www.sparkfun.com/products/10167 although the bus protocol is different to the Maxim one that the iButtons and DS18S20 use.

    If you're OK with using a two wire (I2C etc) bus, then this one might be OK: http://www.sparkfun.com/products/8257 although it's a bit expensive.

    One advantage of the ucontroller method is that it doesn't matter too much what bus protocol sensors use, as you can quickly adapt the code to suit. I have some raw analogue humidity sensors (free, as they were salvaged from old VCRs - every VCR has one by the head to sense excess humidity and shut the thing down). Agin, these are easy to use with a ucontroller logger, as I can just hook them up to an analogue input.
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 12th 2011
     
    borpin: pop into Maplin and get anything that claims to read down to ~2W or less else you may not get meaningful readings on low-power equipment and when testing "sleep"/standby modes, etc.

    I compared a few here:

    http://www.earth.org.uk/note-on-plug-in-power-meters-for-the-UK-REVIEW.html

    None of those exact models may be available but you get the drift.

    Or you can often borrow one for free for a week or two from your local library.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 12th 2011
     
    I am not just after temperature/humidity logging but also power consumption from my CurrentCost meter (currently with 4 CT clamps but about to go to 6).
    The other advantage of going the 'PC' route is that it should be easy to remote access/send by e-mail/web page the data.
    I also have another USB serial device that can allow 2 way communication (though only used it one way the moment).

    Collecting and analysing data is all very well (I love doing it) but can really only be used to show where the problems are and do nothing to change them, apart from though behaviour change, and I have just about gone as far as I can with that (still not got heating on).
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 14th 2011 edited
     
    Out of interest, what sample period are you using?

    I'm running at a 6 minute sample interval at the moment (10 samples per hour on three sensors, all read at the same time), primarily because I'm trying to assess the thermal response of the house and heating system to changes in OAT (one sensor is on the heating flow pipe to a radiator, as I want to see reasonably accurately when the heating goes on and off).

    I'm looking at making an ibutton-like (but bigger) cheap and simple single channel temperature logger, but this might have to be restricted to only 512 samples, rather than the 4096 x 4 samples the bigger logger can manage. Sampling once or twice an hour would be OK, as it'd give 10 to 20 days worth of logging at a time, which is probably OK. I'm wondering if such a slow sample rate would be OK for general environmental logging; my guess is that it would be fine.

    (The reason for the DIY approach is simply that I have some sensors and ucontrollers around and could build a logger like an ibutton thermochron for a fraction of the cost of buying one).
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 14th 2011 edited
     
    Currently using 1 hour spot sampling for the condensation risk ones, did have it at half hour but that is not really worth it.
    One of the things I like about the iButton is that it can be set to sample between 1 to 255 minutes, delayed start so they can be set to sample at the same time, fairly weather proof, and can accept 2048 samples when stand alone.
    If they are wired in the sampling can be done every second (great for those silly experiments). And they are only £15.30, so pretty cheap really.
    The CC device samples around every 6 seconds and can have up to 9 channels plus the base station temperature. Trouble with that is that it needs to be wired to the PC to get that resolution (hence I want a very low power PC as I am using 2.4 kWh/day to just log my usage, though some of that is the wireless router and NAS).

    I also have a LabJack that is very versatile, has I/O, counter, built in temp sensor, 5V power, comparator, I think it can take 1 wire stuff and can sample at what ever rate you choose to about 20,000 Hz I think, costs more, software is a bit odd and fiddly, but can interface with most other software. Mine was about £140 with the software.

    I think the MET office uses both 6 and 10 minute sampling rates, but they are means over the previous minutes, reduced data but higher error.
    SE is easy to work out (SE=Standard Deviation/Square Root of the count of samples) and will almost certainly be smaller than the accuracy of the temp sensor. Though to work out response time I would just look at the slope between two known temperatures when you turn the heating on (good excuse to heat the house up on a cold night). Trouble with working out the house response time is that you have to really mix up all the air or you are just sampling one area (or do multi tests in different rooms) and know the ambient conditions to the same accuracy (or at least know the errors there as well).

    Just for a giggle I 'tested' my kitchen.
    The Descriptive Stats are:
    Count /n 497
    Mean /C 22.0
    Mode /C 24.0
    St Dev /C 2.0
    Min /C 17.5
    Max C 24.8
    SE 0.1
    Slope /C.s^-1 0.002

    And visually:
      Thermal Response Kitchen.jpg
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 14th 2011
     
    The iButton Thermochrons are OK, but as well as the cost (£15 odd for one channel at 2k bytes is more than my four channel, 16k byte logger cost!) there is also the fact that they die after a few years of use (depending on storage temperature and sample rates they might last as long as 8 or 9 years). You also have to buy the special interface cable and USB adapter to use them, as they don't natively talk directly to a PC.

    The two loggers I have built at the moment do very different jobs. One has 8off 10 bit analogue channels (so up to 8 analogue sensors) and logs to an SD card (up to 4Gb) so can store a heck of a lot of data, but it doesn't have a real time clock and can only run down to 1 sample per second (it was built for in-flight monitoring where the required sample rate was around 100 samples per second typically). The real advantage of this little logger is that dumping the data is just a matter of plugging the SD card into a PC and reading a CSV file. Similarly, programming it is a matter of editing a text file on the SD card with the required sample rate etc.

    The one I've just built to log temperature data in the house has four sensor channels (using the same Maxim sensors that the iButtons use, the DS18B20), 16k bytes of memory (could be expanded easily to 64k bytes for a couple of pounds) and can sample at any interval from once every 5 seconds to once every 24 hours (settable in terms of hours, mins, secs between samples).

    The one I'm looking to build as a single channel iButton-like device would cost less than £5, dump data to a serial port as a CSV ASCII file (with no need for any software, just a plain old terminal emulator with a buffer will do) and would run for a long time on ordinary alkaline batteries, or maybe a simple power supply. With a one hour sampling period it would log for around 21 days before running out of memory.
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 14th 2011 edited
     
    ST, FWIW, feeling grotty today so (1) in prep for another piece in The Register and (b) because my W7 laptop that I was reading the iButtons with has just died again which makes two disc failures in 12 months, I'm trying to get to be able to read the iButtons directly on my Linux ARM SheevaPlug.

    Rgds

    Damon
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 14th 2011
     
    Grrrrr, failing to get anything much to work on Mac or Linux...
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 14th 2011
     
    Damon

    I find it best to turn them off, go out, forget all about them. Turn them on again and they work.

    Just out of interest, when you use the W7 laptop, do you cover over the air intake/outlet, I did that on my old one, it lasted a couple of years of infrequent use, but then died. The current one has an extra fan now and is hanging on.

    Take it you have been here:
    http://ubuntuforums.org/showthread.php?t=220436

    All Double Dutch to me.
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 14th 2011
     
    wookey: in desperation I'm now following your advice, two days on, and hoping to do a cut-down version of owfs (without the fs bit).

    Thanks for the steer.

    Rgds

    Damon
    •  
      CommentAuthorDamonHD
    • CommentTimeNov 14th 2011
     
    Have to go to a meeting now, but think I'm getting some traction with the Linux/iButton stuff...

    Rgds

    Damon
    • CommentAuthorborpin
    • CommentTimeNov 14th 2011
     
    Posted By: JSHarrisThe iButton Thermochrons are OK, but as well as the cost (£15 odd for one channel at 2k bytes is more than my four channel, 16k byte logger cost!)

    JSH correct me if I am wrong but this is only for Temp and not humidity like the iButtons. Is there a sensor for the humidity from Maxim?
    Could you do one with an Ethernet port instead of a serial port?
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 14th 2011
     
    The four channel logger I've built would accept any sensor, pretty much. The inputs could be digital (like the one-wire sensors I'm using at the moment) or analogue (like some of the cheap resistive humidity sensors, or light level sensors).

    The commonly available humidity sensors seem to be either cheap resistive ones (as used in VCRs) or Chinese-made one-wire digital sensors that use a different bus protocol from the Maxim/Dallas parts. Either can be hooked up to a suitable logger with a bit of code tweaking.

    Ethernet would be a different kettle of fish, as it would require a fair bit of work to implement. Ethernet protocol isn't something that's easy to implement on a ucontroller, as it carries a pretty big processing overhead.
    • CommentAuthorEd Davies
    • CommentTimeNov 14th 2011
     
    JSHarris: "Ethernet would be a different kettle of fish, as it would require a fair bit of work to implement. Ethernet protocol isn't something that's easy to implement on a ucontroller, as it carries a pretty big processing overhead."

    These are quite cute:

    http://nanode.eu/

    I have one (well, two actually but only made one up so far) but I took a bit of detour off the project planning to use it for now.
    •  
      CommentAuthorJSHarris
    • CommentTimeNov 14th 2011
     
    <blockquote><cite>Posted By: Ed Davies</cite>These are quite cute:

    <a rel="nofollow" href="http://nanode.eu/">http://nanode.eu/</a>

    I have one (well, two actually but only made one up so far) but I took a bit of detour off the project planning to use it for now.</blockquote>

    Mega complicated when compared to my little logger, but certainly neat if you want to integrate something to a house-wide network. I think I'd probably opt for using a simple wireless connection, maybe with a simple BT module, if I wanted to connect directly to a household PC, though, as I'm guessing that wired ethernet is something that will disappear over the next few years.
   
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