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Author Topic: Adapting Decagon EC-5 soil moisture to Arduino  (Read 590 times)
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Hi all,

Looking on the Internet some information about this sensors I found this topic:
http://forum.arduino.cc/index.php?topic=103488.0

From that post the conclusion is that a voltage divider (using resistors) is not working, because there is not enough intensity available for the sensor. I have just checked it and it's correct, the sensor does not work, but if I put 3,3V from a power supply the sensor works. So I'll go for the option of buying a transistor, but my question is... what is better in terms of efficiency and consumption?

My options basically are: transistor PNP or MOSFET? I'm sorry I'm not very good with electronics so far. Could you also let propose what kind of circuit do I have to implement?

Basically, the circuit would be something like the attached image?

For those who are not related with this sensor. I need to excite the EC-5 sensor with 3,3V for 10ms, the problem is that digital pins in arduino provides 5V at 40mA, and the sensor needs at least 10mA, so I want to activate the digital pin and let 3,3v line of arduino go to the sensor, and when the digital pin is deactivated the sensor will not get any voltage.

Thank you very much in advance.

Javier.



* transistor.png (4.29 KB, 240x141 - viewed 21 times.)
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Well, I guess my question has been trending topic on this forum. I would just like to make the point and correct myself saying that IT IS possible to use a voltage divider, just need to do some calculations and choose the proper resitors, and it simply works.

Another issue is the accuracy that you can get with the sensor, taking into account that arduino's ADC is from 0 to 5V. Therefore a signal amplifier circuit is important if you want to get aa accurate measurement.

Regards
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