Soil moisture sensor - using a digital o/p pin as power supply?

Hi,

I'm looking to build a quick and simple soil moisture sensor. A few minutes of googling suggests that the quickest and easiest technique is to measure the resistance of the soil using a pair of metal probes and reference resistor to make a simple voltage divider circuit.

Several posts mention the problem of electrolytic corrosion of the probes, they also mention that a possible solution is to only to turn the sensor on once every 10 minutes or so when a reading is required.

The easiest way to switch the sensor(s) on/off seems to be power them from a digital output on an arduino, according to the spec they can source 10ma per pin.

Will this be enough to power a moisture sensor? and does this seem like a sensible way of turning them on and off?

Thanks

if you do a web search for arduino soil moisture you you get plenty of useful links

Output power from a digital is enough power for a resistance sensor

If you used two analog pins one as the source the other as the drain, 10 minutes later one is the drain the others is The Source

Then you have a continually reversing electrolysis.