{"id":276,"date":"2008-06-03T00:21:44","date_gmt":"2008-06-03T00:21:44","guid":{"rendered":"http:\/\/dalelane.co.uk\/blog\/?p=276"},"modified":"2008-06-03T07:58:44","modified_gmt":"2008-06-03T07:58:44","slug":"currentcost-hacking-starting-to-identify-appliance-power-usage","status":"publish","type":"post","link":"https:\/\/dalelane.co.uk\/blog\/?p=276","title":{"rendered":"CurrentCost hacking – starting to identify appliance power usage"},"content":{"rendered":"

I needed a break from work tonight, so went back to playing with the CurrentCost meter<\/a> – a chance to try a few new things.<\/p>\n

The objective<\/strong>
\nI want to make a start on identifying how much electricity different things in my house use. To begin, I’m going to start with a very manual user-driven approach: <\/p>\n

Subscribe to updates from the CurrentCost meter, and when a significant change in usage occurs, ask me what I’ve just switched on or off, and collect that information to build up a record of how much electricity different devices use.<\/p>\n

How?<\/strong>
\nIt’s already quite late, so I just wanted to hack a quick first version together. I decided to write it as a small Java app. <\/p>\n

As I’ve mentioned before, I’m publishing the CurrentCost readings to a small broker running on my home server<\/a>. The plan was to write a Java application that uses MQTT<\/a> to subscribe to updates from the broker. <\/p>\n

Why? Because I’ve not used Java on the Slug before, or with MQTT. (Is that not a good enough reason? \ud83d\ude42 <\/em>)<\/p>\n

I’ve written it as a command-line app, because it’s a quick way to run it from different devices around the house. (That is, by cheating \ud83d\ude42 I’m actually running the app on the home server, using PuTTY \/ PocketPuTTY<\/a> \/ SSH etc. to run it from my ThinkPad, PDAs, mobile, EEE PC, etc.). <\/p>\n

Step 1 – Get Java on to the Slug<\/strong>
\nI’m using Jikes<\/a> for SlugOS\/LE. I found instructions to set it up on nslu2-linux.org<\/a>, and found the packages via ipkgfind<\/a>: <\/p>\n

wget http:\/\/ipkg.nslu2-linux.org\/feeds\/optware\/slugosle\/cross\/unstable\/classpath_0.97.1-1_arm.ipk\r\nwget http:\/\/ipkg.nslu2-linux.org\/feeds\/optware\/slugosle\/cross\/unstable\/jamvm_1.5.1-1_arm.ipk\r\nwget http:\/\/ipkg.nslu2-linux.org\/feeds\/optware\/slugosle\/cross\/unstable\/zlib_1.2.3-2_arm.ipk\r\nwget http:\/\/ipkg.nslu2-linux.org\/feeds\/optware\/slugosle\/cross\/unstable\/jikes_1.22-1_arm.ipk\r\n\r\nipkg install classpath_0.97.1-1_arm.ipk jamvm_1.5.1-1_arm.ipk zlib_1.2.3-2_arm.ipk \r\nipkg install jikes_1.22-1_arm.ipk -force-depends<\/pre>\n
Step 2 – Get the Java MQTT client library<\/strong>
\nI found a link to a Java client library<\/a> on mqtt.org<\/a>. <\/p>\n
The zip file<\/a> there contains a J2SE\/wmqtt.jar<\/code> which I copied to the server. <\/p>\n
Step 3 – Find some existing Java MQTT client sample code<\/strong>
\nThere is a good developerWorks article<\/a> with source code for writing MQTT subscribers in Java. I started with the Callbacks example<\/a> which gives you enough code to subscribe to the broker, and get the data out of messages received as a byte array.<\/p>\n
Step 4 – Compiling and running<\/strong>
\nTo compile:<\/p>\n
\/opt\/bin\/jikes -classpath \/opt\/share\/jamvm\/classes.zip:\/opt\/share\/classpath\/glibj.zip:\/opt\/mqtt\/java\/J2SE\/wmqtt.jar:. CurrentCostTrainer.java<\/pre>\n
To run:<\/p>\n
\/opt\/bin\/jamvm -classpath \/opt\/share\/jamvm\/classes.zip:\/opt\/share\/classpath\/glibj.zip:\/opt\/mqtt\/java\/J2SE\/wmqtt.jar:. CurrentCostTrainer<\/pre>\n
I did run into a small problem running this, which required me to install the file<\/code> package.<\/p>\n
ipkg install file<\/pre>\n
The reason for this is documented here<\/a>.<\/p>\n
Step 5 – The app<\/strong>
\nThat was pretty much it – the bits of the app that I wrote are fairly trivial. The app runs at the command line, stores the last known reading from the CurrentCost meter, and if a new reading is significantly different from it, it prompts for a description of what changed.<\/p>\n
00:55:46 : I noticed a change of 20W. What did you just switch off? [unknown] : BT Vision\r\n00:56:01 : I noticed a change of 82W. What did you just switch off? [unknown] : TV<\/pre>\n
To save me having to watch the prompt the whole time, I added a line to make it beep to get my attention when it prints a prompt for the user. <\/p>\n
The descriptions entered by the user are being written to a text file. <\/p>\n
dalelane@minipooter:~$ more CurrentCostTraining.xml\r\n<ccupdate>\r\n  <WDiff>9<\/WWDiff>\r\n  <descr>XBox 360 - standby<\/descr>\r\n<\/ccupdate>\r\n<ccupdate>\r\n  <WDiff>55<\/WWDiff>\r\n  <descr>ThinkPad<\/descr>\r\n<\/ccupdate>\r\n<ccupdate>\r\n  <WDiff>54<\/WWDiff>\r\n  <descr>ThinkPad<\/descr>\r\n<\/ccupdate>\r\n<ccupdate>\r\n  <WDiff>20<\/WWDiff>\r\n  <descr>BT Vision<\/descr>\r\n<\/ccupdate>\r\n<ccupdate>\r\n  <WDiff>82<\/WWDiff>\r\n  <descr>TV<\/descr>\r\n<\/ccupdate><\/pre>\n
The source, if it is helpful for anyone, can be found here<\/a>. <\/p>\n
What next?<\/strong>
\nSome ideas…<\/p>\n
Instead of cheating and running the client on the server itself, the query prompts could be properly sent to a mobile<\/b>. <\/p>\n
Previous results could be examined before generating the query, which would let the query prompt include allowing some possible suggestions<\/b>. E.g. “I think you’ve just switched on the television. Is this correct?”<\/p>\n
Comparisons need to be made smarter than just between consecutive CurrentCost measurements<\/b> – it needs to look beyond that to try and identify changes. <\/p>\n
It’s currently based on the simplistic assumption that appliances have a roughly consistent power usage. The next step would be to try and identify curves in power usage graphs<\/b>, rather than just measure initial power surges when you first start a device.<\/p>\n
All in all, it’s a very simple first step… but it’s a start. There is a certain geeky fun in switching something on or off anywhere in your house, and having your phone beep and say “I noticed you switched something on” \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":"
I needed a break from work tonight, so went back to playing with the CurrentCost meter – a chance to try a few new things. The objective I want to make a start on identifying how much electricity different things in my house use. To begin, I’m going to start with a very manual user-driven […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[194,219,213,197,199,200],"class_list":["post-276","post","type-post","status-publish","format-standard","hentry","category-code","tag-currentcost","tag-java","tag-nslu","tag-nslu2","tag-slug","tag-slugos"],"_links":{"self":[{"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=\/wp\/v2\/posts\/276","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=276"}],"version-history":[{"count":0,"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=\/wp\/v2\/posts\/276\/revisions"}],"wp:attachment":[{"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=276"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=276"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dalelane.co.uk\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=276"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}