Aha, maybe a Hall sensor will do? In fact, both meters contain a magnet that is strong enough to trigger a Hall effect sensor. The sensor I use is a A3214EUA-T from Allegro Microsystems (Farnell order code: 1651972).<\/p>\n A test circuit is quickly built and shows that both sensors produce pulses when the meters are rotating. For the gas meter, I get a single pulse per .01 m3. The water meter generates a pulse for every .5 liter of water that is used.<\/p>\n Time to build a more robust circuit to measure the pulses. I decided to build an xPL enabled<\/a> sensor node that can report sensor readings over the local network to my home server. The sensor node reports the readings through the sensor.basic message scheme<\/a> and uses the type ‘count’.<\/p>\n The node is built around a PIC18F2520 and an XPORT. Both are mounted on the netnode PCB<\/a> that I designed previously. PCB and schematics are available here<\/a>.<\/p>\n The software is written in MPLAB and can be compiled with the free version of the Microchip C18 compiler.<\/p>\n The basic idea of the software is to continuously run the function ‘xpl_handler’ from the xPL lib that was written by me and Dirk. All events (sensor triggers, serial IO) are handled through interrupts. To offload the storage of received characters to the receive buffers of the XPORT (that device has 2k buffers built in) a software handshaking is implemented in the firmware.<\/p>\n The sensornode keeps track of the number of pulses that are produced by the Hall sensors and transmits an xpl-trig message when a pulse is detected. The server software can interrogate the accumulated pulses with an cmnd.basic message, after which the sensornode responds with a status message. Code is available in SVN<\/a>.<\/p>\n On the PC side, we need a script to poll the sensornode are regular intervals. This is done with software of choice, and an example Perl script built on the excellent xpl-perl library<\/a> is located here<\/a>. This script pulls the values from the sensornodes and stores them in an RRD database for archiving and graph generation.<\/p>\n The data stored in the RRD database is then graphed. The daily usage statistics look like this:<\/p>\n I have not found a way to include the configuration of the XPORT in the SVN repo. Relevant settings are shown below.<\/p>\n <\/a> <\/a> When built our house, we took measures to ensure that we would consume little energy to keep our place to live warm and cosy. For this, we added extra insulation, we kept the number of air leaks as small as possible, and added a ventilation system that recycles the energy from the extracted air into […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,35],"tags":[],"class_list":["post-720","post","type-post","status-publish","format-standard","hentry","category-embedded","category-xpl"],"_links":{"self":[{"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/posts\/720","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/comments?post=720"}],"version-history":[{"count":23,"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/posts\/720\/revisions"}],"predecessor-version":[{"id":735,"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/posts\/720\/revisions\/735"}],"wp:attachment":[{"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/media?parent=720"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/categories?post=720"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lika.be\/wp\/wp-json\/wp\/v2\/tags?post=720"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"http:\/\/lika.be\/wp\/wp-content\/uploads\/2010\/03\/tellers1-512x401.jpg\" "\\"Water")
<\/a>![\"\"](\"http:\/\/lika.be\/wp\/wp-content\/uploads\/2010\/03\/tellers2-512x402.jpg\" "\\"Gas")
<\/a>Hardware<\/h1>\n
Firmware<\/h1>\n
\nThe device presents itself to the xPL network as ‘hollie-utilmon’.
\nThe next screenshot shows the basic communication between the server software and the netnode for a single sensor readout.<\/p>\n![\"\"](\"http:\/\/lika.be\/wp\/wp-content\/uploads\/2010\/03\/dcm-512x276.png\" "\\"dcm\\"")
<\/a>
\nNext to sensor reporting, the firmware of the netnode also supports initial configuration of the name of the netnode in the xPL network. Filters and group membership is currently not supported.<\/p>\nSoftware<\/h1>\n
Results<\/h1>\n
![\"Gas](\"http:\/\/lika.be\/uushuus_stats\/gas_month.png\" "\\"Gas")
<\/p>\n![\"Water](\"http:\/\/lika.be\/uushuus_stats\/water_month.png\" "\\"Water")
<\/p>\nXPORT configuration<\/h1>\n
![\"\"](\"http:\/\/lika.be\/wp\/wp-content\/uploads\/2010\/03\/Schermafbeelding-2010-03-19-om-20.52.25-512x323.png\" "\\"Schermafbeelding")
<\/a><\/p>\n![\"\"](\"http:\/\/lika.be\/wp\/wp-content\/uploads\/2010\/03\/Schermafbeelding-2010-03-19-om-20.52.40-512x309.png\" "\\"Schermafbeelding")
<\/a><\/p>\n![\"\"](\"http:\/\/lika.be\/wp\/wp-content\/uploads\/2010\/03\/Schermafbeelding-2010-03-19-om-20.52.58-512x155.png\" "\\"Schermafbeelding")
<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"