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The microcontroller in the Arduino has a single sampling capacitor that can be connected to any one of the analog pins.<br>It will charge up to the voltage on the pin if enough charged particles are available on the pin (or a path less than about 10kohm exists to a source of current).<br>The cap is not discharged by the analog-to-digital conversion process or between samples except through leakage.<br>If no charge is available on the pin the capacitor will continue to slowly drain its charge from the previous sample.<br>It's normal and harmless unless you are in a high-voltage environment like a thunderstorm or a nylon carpet, where much more than 5V could accumulate on an open pin. Then it's best to ground unused inputs.<br><br>Martin<br><br><br>> Date: Thu, 12 Nov 2009 18:02:05 +0100<br>> From: altern2@gmail.com<br>> To: pd-list@iem.at<br>> Subject: [PD] arduino problem with analog sensors<br>> <br>> hi<br>> <br>> not a PD question I guess... i dont know much of electrical stuff. i am <br>> connecting two analog sensors to the arduino. One is a pressure sensor <br>> and the second a potentiometer, they are both from an old icube.<br>> <br>> i noticed that when i raise the potentiometer (analog pin 5) the <br>> pressure sensor (analog pin 2) reports values ranging 0 to ~0.16 <br>> increasing together as the potenciometer goes up. It is like some kind <br>> of residual noise comming from pin 5 that goes into pin 0.<br>> <br>> the power cables of both sensors go together to 5v inlet of the arduino <br>> and the ground cables go to ground pin, each of the data cable goes to <br>> its separate analog pin.<br>> <br>> I am using arduino from Pure Data extended using latest Firmata, so i am <br>> just filtering out any value smaller than 0.16 coming from analog pin 0.<br>> <br>> is there anything I am doing wrong? or is this normal?<br>> <br>> thanks<br>> <br>> enrike<br>> <br>> _______________________________________________<br>> Pd-list@iem.at mailing list<br>> UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list<br> </body>
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