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        <s:name>dev/projects/hardware/FS20 Liquid Level Sensor</s:name>
        <s:content>1 FS20 Liquid Level Sensor&#xD;&#xA;In home automation environments there is also the need to measure the liquid level left in a barrel (i.e. rain barrels) and have a notification when the barrel level reaches a critical level.&#xD;&#xA;&#xD;&#xA;A research in the internet showed that the following technologies exist for liquid level (maily water level) measurement:&#xD;&#xA;- resistive measurement by having a series of wires at diferent level placed and if the resistance is nearly 0 Ohm for a given electrode, so this level is flooded.&#xD;&#xA;For this kind of measurement, a series of electrodes are necessary and the level may only be estimated for a range (10%, 20%, 30%, ...)&#xD;&#xA;&#xD;&#xA;- capacitative measurement by having two wires in a specific distance to each other will be put into the liquid and the change of the capacity between this wires will indicate the liquid level.&#xD;&#xA;&#xD;&#xA;- ultra sonic liquid surface measurement will measure the time between sending of specific ultra sonic waves and it&apos;s reflection. There is a promising out of the box sensor {link:SRF02 from Devantech|http://www.shop.robotikhardware.de/shop/catalog/product_info.php?products_id=168} providing all functionality by an I2C / RS232 interface. Also the {link:SRF05|http://www.shop.robotikhardware.de/shop/catalog/product_info.php?products_id=133} is promising and maybe better suitable. {link:useful information about USB and I2C|http://bienonline.magix.net/public/}&#xD;&#xA;&#xD;&#xA;In additional a floating switcher (Schwimmerschalter) will ensure that a water level below a minimal level will be monitored safely. This is important to use the lowest level switch as a pump turn off switch for avoiding damages to the pump.&#xD;&#xA;&#xD;&#xA;1.1 Controller / radio module&#xD;&#xA;The controller will be the {link:CPM|http://www.busware.de/tiki-index.php?page=CPM} module from busware. It communicates with the ultra sonic sensor using I2C and will report the sensor values very similar to [dev/projects/hardware/GardenaBodenfeuchteSensorFS20Modul].&#xD;&#xA;&#xD;&#xA;1.1 Schaltplan&#xD;&#xA;{image:http://knowhow.amazers.net/space/dev/projects/hardware/FS20+Liquid+Level+Sensor/schaltplan}&#xD;&#xA;</s:content>
        <s:mTime>2011-01-15 23:48:53.027</s:mTime>
        <s:cTime>2011-01-01 22:52:48.666</s:cTime>
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                                        <s:date>Sat Jan 15 23:46:53 CET 2011</s:date>
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